Sensuikan: Japanese Fleet Submarines in WW2

Sensuikan: Japanese Fleet Submarines in WW2 Rulebook

Table of Contents

1.0 Introduction
2.0 How to Play
3.0 Game Components
4.0 Game Setup
5.0 Victory Conditions
6.0 Sequence of Play
- [6.1] General Rule
- [6.2] Sequence of Play Outline
7.0 Special Missions and Major Events
8.0 Combat
9.0 Reassignment to a New Submarine
10.0 Multiplayer and Tournaments
11.0 Optional Rules
11.8 Optional Name Generator
12.0 Example of Play
Designer's Notes
Selected Bibliography

1.0 Introduction

The rules of this game have been structured both to make them easy to understand on a first reading and to speed up later reference.

If the player has no experience with or familiarity with historical simulation games, there is no need to be alarmed. First, it is recommended to examine any of the submarine control sheets, the Combat Tables and the game counters; then a quick read-through of the rules should be made. One should not try to memorise the rules. Follow the game set-up instructions and then read section 2.0, which describes the general course of the game. Section 4.0 provides the initial framework for starting to play. As questions arise, simply return to the rules. After a few minutes of play, familiarity with the game's mechanics will be achieved. It should also be kept in mind that most of the game's tables are not even used in some games, or are only consulted once. A sense of being overwhelmed by such a quantity of tables should not be felt, since very few of them will be used depending on the submarine chosen.

Online game assistance is offered. Several options are available: visit the website compassgames.com (the Compass Games home page), or contact Compass Games by e-mail. Compass Games provides general customer service and the replacement of game components (see rule 3.7).

Throughout the rules, numerous indented sections like this one will be included. These contain examples, clarifications, play tips, design notes and other useful remarks intended to facilitate understanding of the text.

Rules cross-references are given in parentheses. For example, one may read: "The total number of torpedoes loaded will always equal the vessel's capacity. Exception: (7.10) Special Mission: Minelaying." This indicates that case 7.10 is related to that rule.

2.0 How to Play

Objective of the Game

The objective of the game is to carry out numerous patrols as commander of a Japanese submarine, to carry out special missions and to sink enemy ships. The success of each patrol is reflected in the total tonnage of ships sunk or in the completion of any special mission, which may lead to promotions in rank and the development of crew skills, culminating in the award of the highly coveted Order of the Golden Kite (Kinshi Kunshō).

The submarine and its crew will face relentless risks, since each patrol will be more dangerous because of the increasing effectiveness of Allied anti-submarine warfare (ASW) as time passes. The ultimate success achieved will depend considerably on the decisions taken on each patrol over the course of the military career. The evaluation of overall victory is determined at the end of the game on the basis of the total tonnage sunk, modified by the special missions successfully completed (which may also be determined posthumously if the captain is killed in combat).

The key game components used to facilitate play are the Submarine Control Sheet, to track the state of the submarine and its crew together with the track boxes of each assigned patrol; the Combat Tables, to resolve encounters with ships; and the Patrol Log Sheet, to record the activity and success of each mission. The various player aid cards are used to resolve the game's functions.

General Description

In general terms, the course of the game is built around carrying out numerous assigned patrols and resolving encounters at sea until the submarine returns safely to port. At the conclusion of each patrol, the success achieved is evaluated by consulting the Patrol Log, which may result in a promotion or decoration for the captain, or a possible improvement in the crew's skill. Between assigned patrols, the submarine will undergo maintenance and refit for one or more months, depending on the damage suffered. It may also need additional time for the recovery of any personal wounds before being in a condition to carry out the next patrol.

Directing Patrols

The Submarine Control Sheet shows the general state of the submarine and its crew, including its armament. When carrying out patrols, the submarine advances through the track boxes on the assigned patrol routes, checking for possible encounters in each track box entered, including the possibility of a random event.

In general, encounters involve contacts with ships or with aircraft. Ship encounters specify whether the enemy vessels are under escort, which plays a fundamental role when engaging them, since the submarine may be detected and exposed to repeated depth-charge attacks. For each ship encounter in which the decision is taken to engage in combat, decisions are made to determine the time of day, whether the combat will be fought on the surface or submerged, and at what range the target ships will be engaged and torpedoes fired. All ships engaged in combat are also recorded on the Patrol Log, noting whether they were damaged or sunk. When making surface attacks against unescorted ships, the deck guns may also be used if the submarine has them.

As combat develops, a roll is made to determine the amount of damage inflicted on the target ships by torpedoes (provided these have not missed) and/or by firing the deck gun.

Although unescorted ships are relatively easy targets, if they are not sunk quickly there is a risk that escorts will appear on the scene when attempting additional rounds of combat to finish them off.

Combat against escorted ships, typically when attacking a convoy, is full of risks, especially if the decision is taken to engage at close range (in which case the escorts may attempt detection before any torpedo salvo can be fired). The escorts will have the opportunity to detect the submarine and, once detected, the submarine may be exposed to repeated depth-charge attacks until it manages to escape further detection. It is even possible to attempt to exceed the test depth in an effort to shake off the escorts. The results of damage, including wounds to the crew, expose the submarine to greater risk while under attack and while trying to escape the escorts' detection.

Once the submarine escapes the escorts' detection, an attempt will be made to repair any damaged system; failed repairs will result in inoperative systems, which could potentially lead to the cancellation of the patrol. Once an encounter with escorted ships ends, there is the option of automatically tracking any damaged ship, or of attempting to engage the entire convoy again.

If a special mission is assigned, the players, in the track box where the mission is to be carried out, will possibly consult one of the three game modules. These modules may be considered temporary "subroutines" of the game in which special rules apply for operating midget submarines, the launch and recovery of aircraft on board, and kaiten operations, or "human torpedoes" (suicide torpedoes). Some special missions simply use the game's normal routines, such as the picket duty task.

Encounters with enemy aviation place the submarine at immediate risk while it attempts an emergency dive to avoid an imminent attack. Should an air attack succeed, anti-aircraft weapons will be used in the hope of damaging or shooting down the enemy aircraft. If the aircraft cannot be damaged or destroyed, there is a risk of suffering further air attacks, or even of escorts arriving in the area to hunt the submarine.

Submarine Refit and Maintenance

Once the submarine completes its patrol by returning to base (after any possible encounter in the last track box of the patrol indicator), it undergoes a period of maintenance and refit. The duration of maintenance and refit depends on the class of the submarine and on the amount of hull damage and inoperative systems requiring repair. In addition, the convalescence of the submarine's captain may cause delays. There is a possibility that a newer submarine will be assigned, or that part of the crew will be lost (because they need more time to recover from their wounds).

During maintenance and refit, it is also possible to evaluate the relative success of the patrol, which may result in an improvement in the crew's level or a promotion, including several decorations. After maintenance and refit, before the submarine begins its next patrol, all systems will be operational and the vessel will be fully resupplied with armament and with a full crew. The submarine could also be bombed during maintenance and refit from January 1944 onwards.

End of the Game

Once all patrol assignments up to July 1945 have been carried out, the game ends. In addition, if the player, as captain, is killed in combat, is captured, or if the submarine is sunk, scuttled or captured, the game ends immediately. Whether the player survives to the final patrol or not (ending after July 1945), the total tonnage of the sunk ships is tallied to determine the level of victory achieved and is adjusted according to the special missions successfully completed. In general, to record a complete military career, one should note all the ships sunk (including large warships), the final rank and the decorations obtained. Of course, if the player has gone down with the submarine, any awards and results will be recognised posthumously.

3.0 Game Components

[3.1] Submarine Control Sheet

The 9 Submarine Control Sheets (printed on both sides, for a total of 18 sheets) correspond to each class of Japanese submarine available to players. These include the specific patrol routes with their respective Track Boxes to track the progress of the mission. This sheet makes it possible to monitor and record the state of the crew and of the systems, including the available armament. The player selects the Control Sheet corresponding to the type of submarine chosen for the game. This sheet is the central element in developing the game and carrying out patrol missions. The use of this component is detailed in the corresponding section of the rules.

[3.2] Combat Sheet

The Combat Sheet [H1] is used to resolve combat against naval targets and is generally placed next to the Submarine Control Sheet during play. The use of this tactical board is detailed in the corresponding rules section.

[3.3] Game Counters

The game counters (markers) included with Sensuikan are supplied on two punched counter sheets. These counters are placed on the Submarine Control Sheet to track the state of the submarine and its crew, or on the Combat Sheet when resolving encounters. Counters are provided for individual ships, aircraft, crew members, individual torpedoes, ammunition shells, random events, and the state of the crew and systems.

Note: additional counters have been printed — for example, additional torpedo counters — as spares in case any are lost or damaged.

[3.3.1] How to Read the Counters

The set of Sensuikan counters provides markers for tracking the state of the submarine and for resolving combat. These markers may include information, such as modifiers to the dice roll, to facilitate play. An explanation of each type of counter is given below.

[3.3.2] Counter Types

Submarine: The submarine counter corresponds to the model the player has selected and is placed on the Submarine Control Sheet to track progress along the assigned patrol route. Each of the 17 submarine markers indicates its corresponding type.

Officer Rank: Three numbered officer rank markers (from 1, the lowest, to 3, the highest) are provided to track the player's level of promotion as submarine captain.

Medals and Decorations: Various medals, decorations and insignia may be awarded to the player depending on the success of his military career.

Crew Quality: Crew quality corresponds to the experience and performance of the player's crew. The crew begins at the "Trained" level. This level may rise to "Veteran" and then to "Elite", or may drop to "Green" (Novata).

Random Events: Although most random events are resolved immediately, some may be used later in the game, so these markers are to be placed on the Submarine Control Sheet until used.

Skills: Skill markers increase the player's chances of survival and success, and are obtained at the submarine school or by the player's choice every 3 successful missions.

Armament: Torpedo markers represent individual torpedoes by type. These are: Type 89 (steam), Type Year 6 (steam), Type 95 (oxygen) or Type 92 (electric). Midget submarines use a smaller 18-inch torpedo, the Type 97. Ammunition markers record the number of shells available for each deck gun.

Additional Markers: Additional markers include supplies, midget submarines, Kaiten, aircraft and a wide variety of other items.

Damage: Markers are provided to record damage to the hull, the level of flooding and any possible damage to engines and other systems. These markers are placed on the Submarine Control Sheet only when damage occurs.

Note: both system-specific counters, bearing the name of each system, and generic counters are provided. It is recommended to use the specific damage markers to track which system or systems are damaged or inoperative (useful in case the Submarine Control Sheet is moved accidentally and the markers shift).

Crew Status: Markers are provided to record the severity of wounds or the results of combat casualties (KIA). Specialist crew members may also be promoted to the "Expert" level (11.1), which provides certain benefits during play.

Combat Sheet Markers: Markers are provided for the Submarine Combat Sheet [H1] when resolving sightings. These markers include Day/Night, the range of the engagement, the type of ships set as targets, and markers for the quality of escorts and of aviation. Note that torpedo and ammunition markers are consumed and are moved from the Submarine Control Sheet to the Combat Sheet when resolving combat.

Terminology note: "DRM" (dice roll modifier; "MTD" in the Spanish text) means a dice roll modifier and is used throughout the rules and tables to indicate a whole number that modifies the result of a die or dice roll up or down. Whenever a result is modified above or below the indicated results because of a DRM, the maximum or minimum possible result, respectively, is considered obtained.

[3.4] Player Aid Sheets and Tables

Thirteen sheets are provided, containing game aid tables printed double-sided, plus one sheet printed on one side only, to facilitate play and to resolve the functions of the game.

Missing from this transcription: the player-aid and combat table sheets themselves (including the Combat Tables [A1]-[A4], [B1]-[B7], [T1]-[T5], [M1]-[M7], [K1]-[K3], [P1]-[P12], [F1]-[F4] and [H1]-[H2] referenced throughout these rules) are not contained in the source document, which is the Spanish rules text only. Their contents cannot be reproduced here, so any rule that depends on them cannot be carried out from this file alone. The use of these charts and sheets is detailed in the corresponding section of the rules. Specific charts and tables are referenced by their identifier in [square brackets].

When a dice roll is required, each table specifies the dice combination needed; in some cases this may include each die representing a different positional value. In such cases a die of a different colour should be used to distinguish the positional values. For example, for a roll of "1d10+1d10", the first d10 represents the tens value and the second d10 the units value. A result of "00" must be treated as "100", not "0".

[3.5] Patrol Log Sheet

The Patrol Log Sheet is used to record, in each play session, the type of submarine, its identification and the name of the captain, together with the individual patrol missions, the ships damaged or sunk, and the duration of maintenance and refit after each patrol. These sheets may be photocopied as needed.

[3.6] Game Scale

Each track box on the Submarine Control Sheet represents approximately four to six days of patrol. Generic crew boxes represent several of the approximately 70 to 100 men on board. Certain specific markers represent individual ships, aircraft, specific crew members, individual torpedoes and rounds of ammunition.

[3.7] Inventory

A complete set of Sensuikan includes the following components:

Two sheets of full-colour game counters.
A rulebook with designer's notes.
13 player aid sheets (Tables), printed double-sided.
One player aid sheet, printed on one side.
A pad of Patrol Log Sheets.
Nine Submarine Control Sheets (covering 17 submarine classes and one midget submarine), printed double-sided.
An operations map.
A Combat Sheet.
Two six-sided dice, one twenty-sided die and two ten-sided dice.
A game box with lid.
A set of game sequence cards (7 cards in total).

If any of these components is missing or damaged, please contact the publisher, Compass Games (see section 1.0).

4.0 Game Setup

General Rule

Game setup consists of selecting the type of submarine, preparing the Patrol Log and placing the corresponding Submarine Control Sheet in front of the player for the initial placement of markers before carrying out the first patrol. The Combat Tables should also be kept at hand, since they will be consulted when resolving encounters with enemy naval targets.

Table [K1] tracks the state of the commander and crew, as well as any skills they possess that affect play. The operations map shows the different areas of the Pacific in which the submarine will operate, together with any additional transit time required to reach distant patrol track boxes.

[4.1] Choice of Submarine Model

Begin by selecting one of the seventeen submarine types that the player wishes to command, placing the corresponding Control Sheet in front of the player. Only one submarine type should be selected. See [4.2] Start Date to check which submarine types are available on which dates. Earlier start dates allow more patrols to be carried out, while later start dates offer more advanced submarines. Play consists of embodying the commander of a single submarine, rather than simulating the control of several submarines on patrol.

Note: one may start with a more advanced model, such as the Type A (Modified), but this will not become available until May 1945, meaning the first months of the war will not be available to accumulate a higher score.

[4.2] Start Date

[4.2.1] The first patrol will begin in December 1941, unless a submarine type is chosen that is not available until later in the war.

[4.2.2] Availability dates are given for the whole war and are listed in chronological order for each submarine type:

Submarine type	Available from
Kaidai KD.3	December 1941
Kaidai KD.4	December 1941
Kaidai KD.5	December 1941
Kaidai KD.6	December 1941
Kaidai KD.7	September 1942
Junsen J.1M	December 1941
Junsen J.2	December 1941
Junsen J.3	December 1941
Kirai-Sen	December 1941
Tipo A (Type A)	December 1941
Tipo B (Type B)	December 1941
Tipo C (Type C)

Note: when a rule specifies Type A or Type B submarines, it refers only to the Type A and Type B submarines specifically, and not to the Type A (Modified) or Type B.3 variants.

[4.2.3] Under certain circumstances the commander may be reassigned, or may choose a more modern submarine model; however, in general he will remain in command of the same submarine until the end of the game or until it is sunk.

[4.3] Preparing the Patrol Log Sheet

[4.3.1] A narrative of your naval career should be prepared by recording the following information in the header of the Patrol Log Sheet:

Submarine class: corresponds to the submarine model chosen.
Identification (ID): usually designated "I-###".
Commander: the name chosen for the submarine's commander.

Note: the name of the submarine and the name of the commander have no impact on play, but help to create a narrative of your military career and to enrich the play session or later reports.

Optional: see section (11.6) for the historical submarine listing.

[4.3.2] The Patrol Log Sheet is used to record information about each assigned patrol, including which target ships were damaged or sunk, in order to help determine the level of victory achieved (5.2).

[4.4] Setting Up the Submarine Control Sheet

[4.4.1] Place in front of the player the Submarine Control Sheet corresponding to the type of submarine selected (see the example below). This sheet will be consulted constantly during patrols to record the state of the submarine and of the crew.

[4.4.2] The following markers should be placed on the Control Sheet:

Place the crew quality marker at "Trained" (Entrenada) in the crew quality box. This is the initial crew quality.
Place the submarine marker in the "In port" box (maintenance and refit) (located on the left side of the sheet), and place the current patrol marker on the map at the corresponding port.
Place the appropriate torpedo and deck gun ammunition markers in the armament section of the Control Sheet (4.5 and 4.6).
Place the starting base marker on the Control Sheet.

[4.5] Torpedo Loading (Stowage)

Comment: Japanese submarines normally carried a full load of 21-inch Type 95 oxygen torpedoes. These were the submarine versions of the feared "Long Lance" torpedo launched from surface ships, and they left a minimal wake. However, at the start of the war it was necessary to exhaust the stocks of the older steam torpedoes, Type 89 and Type 6. During the war an electric torpedo, the Type 92, was developed. The older steam torpedoes and the oxygen-propelled torpedoes ran at higher speed than the electrics and were therefore somewhat more accurate. The electrics were slower and therefore had a slightly lower probability of hitting at long range, but they left no trail of steam bubbles that could guide escorts to the submarine. This made them much better than steam torpedoes, and a little better than oxygen torpedoes, for use during the day, in order to reduce the possibility of detection by escorts. The electrics, although apparently inferior to the oxygen-propelled Type 95, were cheaper and easier to manufacture. Midget submarines used a scaled-down 18-inch diameter torpedo, the Type 97.

Procedure

Consult the initial load information on the Submarine Control Sheet.
Select a number of torpedo markers equal to the total load.
Until 7/42 (July 1942), the Kaidai (KD) and Type B classes will load 12 Type 6 torpedoes, the rest being Type 95.
Until 7/42, all other submarine classes must roll 1d6. On a result of 1-3, they must load 12 Type 89 torpedoes, with the rest of the load being Type 95. On a result of 4-6, they will load all Type 95 torpedoes.
From 7/42, it is assumed that stocks of the older torpedoes have been exhausted, but electrics are now available in quantity. All classes may load up to 6 Type 92 torpedoes, with the rest of the load being Type 95.

Example: The Type A class carries a total load of 18 torpedoes. Of these, the initial mix by torpedo type before 7/42 would be 12 Type 89 torpedoes and 6 Type 95 torpedoes if a 1-3 was rolled. It would be 18 Type 95 torpedoes if a 4-6 was rolled. From 7/42, the load would be up to 6 Type 92 (at the player's choice) and the rest Type 95.

Place individual torpedo markers in the numbered boxes corresponding to the bow and stern tubes. Remember that only one marker is permitted per box.
Place the remaining torpedo markers in the bow and stern reload boxes. Check the total capacity of the reload boxes and ensure that the number of torpedo markers equals that capacity value.
The total number of torpedoes loaded will always equal the submarine's capacity. Exceptions: (7.4) Transport Special Mission; (7.6) Evacuation Special Mission; (7.10) Minelaying Special Mission.
Torpedoes, once loaded and placed on the Control Sheet, may never be exchanged or transferred between the bow and stern positions. Only reloading is permitted.
Once torpedoes have been fired from the bow or stern tubes, they may be reloaded after combat. The bow torpedo tubes are reloaded with the torpedoes contained in the bow reload box. Likewise, the stern torpedo tube is reloaded with the torpedoes contained in the stern reload box.
Midget submarines always carry two Type 97 18-inch torpedoes. There are no reloads for midget submarines.

Reloading can only be carried out if torpedo markers remain in the corresponding reload box. Once a section's reload box has been exhausted, no further reloads are possible for the rest of the patrol.

[4.6] Ammunition Markers

[4.6.1] The Control Sheet is used to track the total number of deck gun ammunition shells available, up to the limit of its capacity.

[4.6.2] Initially, enough ammunition markers are placed in the deck gun ammunition box so that the point value equals the total ammunition capacity indicated.

[4.6.3] Each point value of an ammunition marker represents one round of ammunition for the gun combat. Up to two points of ammunition (or rounds) may be expended per combat round for each deck gun.

Note: each deck gun "round" of ammunition in the game represents roughly 25 real shells.

[4.6.4] Bomb markers represent the small bomb load that seaplanes sometimes carry, available in certain submarine classes. These are only placed on the aviation Control Sheet if the submarine has been given a bombing mission.

[4.6.5] Ammunition markers are not used for anti-aircraft weapons, since these have an unlimited supply (for game purposes).

Note: anti-aircraft weapons have no associated ammunition box; only the status of the weapon is tracked on the Control Sheet.

[4.7] Operations Bases

The submarine will have its operations base in one of five locations available during the game:

[4.7.1] Yokosuka. One of Japan's main naval bases. All initial submarines are considered to start here.

[4.7.2] Paramushiro. Japan's main northern base, and the base from which patrols to the Aleutians generally departed. If a patrol is assigned to the Aleutians and the submarine does not currently have its base at Paramushiro, it is first reassigned here and then departs on patrol. All subsequent patrols will be to the Aleutians until 7/43 (July 1943), at which point any submarine stationed here will be reassigned to Truk.

[4.7.3] Truk. Truk was unquestionably Japan's key central base in the Pacific. It ceased to function as a base in 3/44 (March 1944). Any submarine stationed there must change its base to Yokosuka if its patrol ends in 3/44 or at a later date. If it is in maintenance and refit at Truk when 3/44 occurs, the submarine is assumed to be lost, and the player loses one month while travelling to Yokosuka and receives a new submarine of his choice (if available at that time).

[4.7.4] New Guinea. Several bases operated in the New Guinea area, mainly Rabaul and Shortland. Although isolated by the Allied "island-hopping" strategy, these bases remained active until the end of the war.

[4.7.5] Dutch East Indies (DEI). Japanese raids into the Indian Ocean were organised from the Dutch East Indies. Several bases remained active, and the abbreviation "DEI" stands for any of them, including Singapore, Penang and Sabang.

[4.7.6] Air raids on ports. From January 1944, during the maintenance and refit phase, the presence of air raid damage must be checked when the submarine is in any port, with the exception of Paramushiro. Roll 2d6:

Roll	Air raid result
2	Submarine destroyed in the air raid. One month must be spent travelling to a new vessel in Yokosuka.
3	Submarine severely damaged in the air raid. Add 2 months to the current maintenance and refit.
4	Submarine damaged in the air raid. Add 1 month to the current maintenance and refit.
5-12	No effect.

[4.8] Training Schools

Before the game begins, the player must attend the Kure Submarine School (and, if applicable, the Midget Submarine School and the Kasumigaura Naval Aviation School). These schools grant possible initial skills to the various crew members and to the commander.

[4.8.1] Kure Submarine School, Table [F1]. A training roll must be made for the commander, his second-in-command and his engineer. Any skill marker obtained is placed on the Log Sheet [K1]. In addition, the player must choose one of three options for using his free time at the school; each one grants a different game benefit. Only one of the three options may be selected.

[4.8.2] Midget Submarine School, Table [F2]. Only if the submarine is equipped with a midget submarine (Type C class) is the roll made in this section. The skills actually belong to the midget submarine's commander, who travels on board until the midget submarine is launched, but they are tracked on the Captain and Crew Status record [K1]. If the midget submarine's commander is killed or lost, a replacement will be received during the next maintenance and refit. This replacement will also attend the school first. This type of submarine is only carried if the current patrol has a major event marker, and that marker has a midget submarine mission on its reverse side.

[4.8.3] Kasumigaura Naval Aviation School, Table [F3]. Only if the submarine is equipped with aviation is the roll made in this section. The skills belong to the aviation pilots, but are tracked on the Captain and Crew Status record [K1]. If the submarine carries several aircraft, the roll is made separately for the pilot of each aircraft. If any pilot is lost, replacement pilots will arrive during the next maintenance and refit, but they too will attend the school first.

[4.8.4] Kaiten Training School, Table [F4]. Only if the submarine is to carry out a Kaiten mission is the roll made in this section. Furthermore, as these are suicide missions, a roll must be made for a new set of possible skills before each Kaiten patrol, since the previous Kaiten operators will have died.

5.0 Victory Conditions

General Rule

A complete campaign consists of carrying out numerous patrols through July 1945 inclusive.

The game may end early if the submarine is sunk, or if the commander dies in action or is captured after scuttling the submarine.

Although the results of each patrol may lead to promotions and to improvements in the crew's quality (or, conversely, to a decline in crew quality due to poor performance), the overall level of victory is determined at the end of the game on the basis of the total tonnage of ships sunk.

[5.1] End of the Game

[5.1.1] The game ends upon completion of the last patrol through July 1945 inclusive; no patrol assignments are made after July 1945.

[5.1.2] If, when calculating the maintenance and refit period, it is determined that the next patrol will begin after July 1945, the game ends.

[5.1.3] The game ends immediately, regardless of date, if the commander dies in action or is captured as a prisoner by the enemy.

[5.1.4] Once the game has ended, the level of victory is determined.

[5.2] Determining Victory

[5.2.1] The Patrol Log Sheet is consulted at the end of the game, and the total tonnage of ships sunk during the service record is added up.

[5.2.2] Based on the total tonnage of enemy warships and naval targets sunk, the level of victory (adjusted by the special missions) and the performance as a submarine commander can then be determined:

DEFEAT: 0 to 9,999 tons sunk, or if the submarine is captured because of a failed scuttling attempt (voluntary sinking). Note: at the moment the submarine is captured because of a failed attempt to scuttle the vessel, an automatic "Defeat" is declared, regardless of the tonnage of ships sunk and the special missions completed. "You are a disgrace to the Emperor, your ancestors, your family and yourself. If you have survived, you will return to the bombed ruins of your home to contemplate your mistakes."
DRAW: 10,000 to 19,999 tons sunk. "You have fulfilled your obligations to the nation. Your neighbours sometimes regard you with suspicion or subtle social disapproval."
MARGINAL VICTORY: 20,000 to 49,999 tons sunk. "You have achieved a modest success on your record as a submarine commander. Your crew respects your abilities and skills."
CONSIDERABLE VICTORY: 50,000 to 99,999 tons sunk. "You are one of the best officers of the elite submarine force of the Imperial Japanese Navy, and you have earned the respect of your comrades, your crew and your commanders. You are often mentioned in the nation's newspapers, and in 1945 you are offered command of a Sen-Toku class submarine."
DECISIVE VICTORY: 100,000+ tons sunk. "You are the scourge of the seas and the pride of the entire Imperial Navy. Your legendary exploits place you at the pinnacle of the naval elite, and you are prominently mentioned in propaganda media. Your comrades are astonished at your bold successes. After the war, you return to the bombed ruins of your hometown and wonder what it was all for."

[5.2.3] Your level of victory rises one step for every 10 special missions successfully completed.

[5.2.4] If the commander dies in combat, the level of victory is determined posthumously. The same procedure applies if he is taken prisoner of war.

6.0 Sequence of Play

[6.1] General Rule

Sensuikan follows a defined sequence of play for carrying out successive patrols. At its most schematic level, the sequence consists of carrying out patrols, followed by a period of maintenance and refit at the end of each patrol. Although there are no numbered "game turns" as in other turn-based systems, the game is divided into monthly increments, as reflected on the Patrol Log Sheet. The game begins on the availability date of the selected submarine class (first assigned mission), and patrols follow one another through July 1945 (7/45). Completing each patrol takes at least one month, while the number of months required for maintenance and refit may vary depending on the circumstances (submarine class, amount of damage and/or crew injuries).

The following sequence of play applies once the submarine has been selected and all markers have been placed on the corresponding Control Sheet (4.0, Game Setup).

[6.2] Sequence of Play Outline

1. Determine the assigned patrol

A. To start the game in December 1941, the active Major Event markers are placed on the map, specifically at Pearl Harbor, the Dutch East Indies, Malaya and the Philippines. Likewise, any Major Event markers that have expired are removed from the board.

B. The Patrol Assignment Table [A1] is consulted to determine the current assignment. C. The patrol assignment is recorded on the Patrol Log (in the row corresponding to the patrol's start date), and it is checked whether there is a special mission assignment if the patrol is heading to an area with an active Major Event marker. If the submarine is capable of carrying out that type of special mission, that will be the assignment. If the submarine cannot carry out any of the special missions indicated, it is simply considered to be on patrol in that area. The special missions are listed on the reverse of each Major Event marker.

D. The submarine marker is placed on the map in the first track box of the assigned patrol.

Map note: several patrol areas on the map involve a much longer transit to reach than others (Australia, Europe, Hawaii, the US West Coast, etc.). The map shows additional Transit boxes for these areas. Encounters must be checked in these map transit boxes as well as in the Transit boxes on the Control Sheet.

2. Conduct the patrol

A. Patrols consist of moving through a number of track boxes, with the possibility of carrying out a special mission, and then returning to base. Track boxes are divided into two types: "Transit Boxes" (long-distance voyages with a low probability of contact) and "On Station" boxes. Each patrol begins (and ends) with a Transit Box, as shown on the Control Sheet. Any special mission will be carried out in the first "On Station" track box.

Some patrol areas are quite distant from Japan, and travel there will involve additional track boxes (shown on the operations map, but not on the Control Sheets). These areas are Pearl Harbor, the US West Coast, Australia, the Panama Canal and Europe.

Important note: these additional track boxes on the map reduce the number of "On Station" boxes for that patrol, and they are split evenly between the start and the end of the patrol (if there are 3 additional Transit Boxes, they are distributed as 2 at the start and 1 at the end).

Example: a Type C class submarine begins the war heading to Pearl Harbor. The Type C Control Sheet has one Transit box, five On Station boxes and one final Transit box. Because of the additional Transit boxes to Pearl Harbor, this patrol effectively consists of two Transit boxes, three On Station boxes (in the first of which the midget submarine is deployed), and then two final Transit boxes.

If the Type C had been sent to the US West Coast, the patrol would consist of three Transit boxes (1 normal + 2 additional), followed by two On Station boxes, followed by the 2 final Transit boxes (1 normal + 1 additional).

As a last example, if the Type C begins the war heading to the Dutch East Indies, the patrol is carried out exactly as shown on the Control Sheet, since there is no additional transit time. It would therefore consist of one Transit box, five On Station boxes and one final Transit box.

B. Check for encounters in each occupied track box by consulting the Encounter Table [A3]. If no encounter occurs, repeat this step for the next track box entered. If an encounter is obtained on the roll, the following steps must be followed:

Encounter resolution

a. Determine the random event (if obtained on the roll, Table [B11]), or resolve the naval or aerial encounter (8.0). Engaging enemy ships in combat is always voluntary.

b. Additional rounds of combat may be carried out if necessary against unescorted ships (8.2.8), or the submarine may attempt to "Track" escorted ships or convoys (8.4), until the encounter ends, reloading torpedoes between rounds.

c. Additional rounds of combat may also occur if the submarine is detected and subjected to repeated depth-charge attacks. This cycle repeats automatically until the submarine escapes the detection of the escorts or is sunk.

d. An attempt must be made to repair any damaged system of the submarine once all combat rounds have concluded (8.5).

Note: "Tracking" of damaged ships is still permitted once the submarine has escaped detection, even if it has been through many rounds of depth-charge attacks.

C. The submarine must advance to the next track box and repeat the process until it enters and resolves any possible encounter in the final track box. On completion, the submarine marker is placed in the "In Port" box (maintenance and refit).

Terminology note: all the boxes on the map are track boxes. However, some track boxes are called "transit" boxes; these are found at the start and end of a patrol. Track boxes in the patrol area of the mission may be called "on station" track boxes. The first track box that is not a transit box is sometimes called the "mission box". Regardless of name, they are all still track boxes.

3. Refit of the submarine

A. The damage to the submarine and the duration required to complete all repairs (8.5.10) are evaluated. The duration of the refit is recorded on the Patrol Log by writing an "R" in each month of maintenance and refit, so that it can be determined when the next patrol will begin. Note that the different submarine classes have different different patrol durations: some are two-month patrols and others are three-month patrols. To reflect this, a "P" is added in the month after the patrol for submarines with two-month patrols, and another "P" is added in the month after that for submarines with three-month patrols. This indicates that the submarine is still on patrol during those months. After the last month marked with a "P", an "R" is placed for each month of required maintenance and refit. Normally this is one month, but it may be extended by the damage suffered by the submarine.

Note: if the start date of the next patrol is after 7/45 (July 1945), the game ends.

B. Refit sequence (as printed). The following items are checked during the refit, in order:

A. Crew recovery and possible replacements are checked (8.5.9.1).
B. Crew quality improvement is checked (8.7).
C. Awarding of decorations and/or promotions is checked (8.8 and 8.9).
D. The possible reassignment of the submarine is checked (9.0).
E. The submarine is resupplied, its torpedo loads are configured (4.5) and its ammunition markers are replenished (4.6) for the next patrol. All damage and crew wound markers must be removed from the Submarine Control Sheet in preparation for the next patrol.
F. The possible removal of the deck gun/aviation and the installation of Kaiten are checked (7.12).
G. Possible bombing damage from January 1944 onwards is checked (4.7.6).

The game proceeds according to the above sequence until the game ends (see 5.1), at which point victory is determined (5.2). These activities are dealt with in the respective sections of the rules.

7.0 Special Missions and Major Events

There are many special missions in the game that reflect the concepts of the Japanese high command on the employment of its long-range submarines. These missions are linked to the Major Event markers active on the map. If a submarine is assigned to a patrol in which a Major Event is active at that time, it will have a special mission, which will be carried out in the first track box of the patrol that is not a transit box. If the patrol is toward an area where there is no Major Event in progress, or if the submarine is incapable of performing the type of special mission required, then it will carry out a normal patrol.

Special missions, when successfully completed, count as two successful patrols instead of one for the purposes of acquiring skills and for improving the crew's level. This also applies to a patrol in an area with a Major Event marker if the marker indicates "Patrol", even though such a patrol is not technically a special mission.

If the submarine can perform more than one special mission listed on the reverse of a Major Event marker, it is assigned the first mission on the list for which it is qualified, proceeding from top to bottom on the marker.

Some special missions (those involving aviation, midget submarines or kaiten) require the use of the corresponding module.

[7.1] Reconnaissance

A reconnaissance mission requires (only) that a submarine equipped with aviation launch its aircraft and carry out a (theoretical) reconnaissance of the area. Therefore, not all classes will be able to carry out this mission. The Aviation Module must be consulted upon reaching the first non-transit patrol box (the "mission box"). After resolving the aircraft's mission under the rules of that module, the mission succeeds if one or more of its aircraft survive (whether recovered or not). An aircraft is considered recovered in that same track box if it passes the recovery roll.

[7.2] Picket Duty (Picket Line)

This mission requires the submarine to form part of a picket line (in military jargon, "línea de descubierta"), with the aim of intercepting US forces heading into or withdrawing from an area. Essentially, the submarine remains stationary (in the same place), hoping to locate a warship as a target. In game terms, the main effect of being on a picket line is that the submarine is not allowed to engage in combat or to track any merchant traffic it may encounter. Success in picket duty requires having engaged in combat with at least one warship or capital ship (sinking it is not mandatory).

[7.3] Midget Submarine Attack

This mission requires the submarine to release its midget submarine near a port, after which the midget submarine will carry out an attack against the warships moored there. The mission is considered a success if the midget submarine is released and attacks at least one ship; any damage it may or may not inflict is irrelevant to success, and it is not necessary for the midget submarine to survive. However, any tonnage the midget submarine manages to sink is added to the submarine's total for victory points and decorations. The mission is also considered a failure if the midget submarine cannot be deployed (because of damage to the craft itself, or because of the death or serious wounding of the midget submarine's crew before reaching the mission box). Whether the midget submarine actually damages any merchant or warship is again irrelevant to calculating mission success; it only matters that it has been deployed and has engaged something. Midget submarine attacks are resolved by consulting the Midget Submarine Module.

[7.4] Transport

Successful completion of this type of special mission requires the delivery of supplies (to Guadalcanal or New Guinea, for example). When assigned to supply transport, the submarine has its torpedo tubes loaded, but carries no reloads.

The "Supplies" marker must be placed in the reload area. To deliver the supplies, the submarine must make a roll on the Special Missions encounter column of Table [A3] upon reaching the first non-transit patrol box (a process similar to that of a reconnaissance mission). If no encounter occurs, the supplies are delivered and the mission is a success. If an encounter occurs, it is resolved, and the submarine must then roll again until there is no encounter and the mission is completed.

[7.5] Strategic Transport (to Europe)

This mission applies only to Type A and Type B submarines; for any other type, re-roll. These missions were code-named "Yanagi" (Willow) missions. The submarine has been selected to deliver strategic minerals and supplies to a German-controlled port in France. It must set course for the Indian Ocean transit boxes pointing towards Europe and then make one roll per box for an encounter in the Special Missions / Additional Combat Round section of Table [A3]. At that point, Europe will have been reached. The process must be reversed to return to Japan. This patrol lasts 3 months in each direction. The patrol is considered a success if the supplies are delivered in Europe.

[7.6] Evacuation

Evacuation missions require the submarine to travel to the Aleutian Islands and help evacuate Japanese personnel from the islands. When assigned to an evacuation mission, the submarine has its torpedo tubes loaded, but carries no reloads. The submarine must make a roll in the Special Missions encounter section of Table [A3] upon reaching the Aleutians, since it is more vulnerable while embarking passengers. If no encounter occurs, the passengers are embarked and the patrol is a success, assuming the submarine returns to base with the passengers unharmed. If an encounter occurs, it is resolved, and the submarine must then roll again until there is no encounter and the mission is completed. The passenger counts as a pilot on the Crew Wounds Table.

[7.7] Bombing Mission

Although somewhat misguided in concept, some Oregon forests were bombed by aircraft launched from submarines in the hope of causing large forest fires. Late in the war, a plan to bomb the Panama Canal was also considered. To carry out either mission, the submarine must travel to the West Coast or Panama track box, as appropriate, then launch its aircraft and make the bombing run according to the Aviation Module. The mission is a success if the bombing takes place, even if no ship is sunk in the rest of the patrol and even if the aircraft is lost. If no bombing takes place, the mission is considered a failure, even if other ships were sunk during the patrol. Only the Type A (Modified) and Sen-Toku classes will be assigned the mission to bomb the Panama Canal.

[7.8] Kaiten Attack

This mission requires the kaiten to be released near a port, after which they carry out an attack against the warships moored there. The mission is considered a success if the kaiten are released without the submarine having been detected; any damage they may or may not inflict is irrelevant. The mission is also considered a failure if no kaiten can be deployed (because of damage to the craft themselves, or because of the death or serious wounding of the kaiten crews before reaching the mission box). However, any tonnage the kaiten manage to sink is added to the submarine's total for victory points and decorations. Kaiten attacks are resolved using the Kaiten Tables sheet. Being a suicide weapon, the kaiten and their crews are considered lost regardless of whether the targets are hit or missed. Kaiten missions are carried out by consulting the Kaiten Module once the submarine arrives at the location of the Major Event marker.

[7.9] Coastal Bombardment

Coastal bombardment requires that the submarine surface within range of the deck gun off the west coast of the United States and expend all of its deck gun ammunition (theoretically, this is done by simply removing all deck gun ammunition markers). The mission is considered a success if the submarine returns to base. Again, as in most special missions, a roll must be made in the Special Missions section of the Encounter Table [A3] before the attempt, and the submarine must survive any encounter before the shelling can take place. If an encounter occurs, it is resolved, and the submarine must then roll again until there is no encounter and the mission is completed.

[7.10] Minelaying

This mission requires that mines be carried stowed in the torpedo tubes. This reduces the torpedo load by an amount equal to the number of tubes used. When the mines have been successfully laid, the tubes may be reloaded with torpedoes.

Note: the Kirai-Sen class is a specialised minelayer and has special mine compartments, from which mines are laid from the rear of the submarine by means of a stern dispenser. This class does not reduce its torpedo load in a minelaying patrol and, in fact, every patrol with a Kirai-Sen class submarine is automatically a minelaying mission, even if otherwise indicated on the Patrol Assignment Table. Unlike other classes, the Kirai-Sen class does not receive the credit equivalent to two successful patrols for carrying out minelaying work.

To carry out this mission, the submarine travels to the first track box of its area. On arrival, a roll is made in the Special Missions section of Encounter Table [A3]. If no aircraft appears, it is assumed that the mines are laid. If an encounter occurs, it is resolved and the roll is repeated until the area is finally clear and the mines can be laid. After laying the mines, the rest of the patrol is carried out normally, and it is considered a success, regardless of whether any tonnage is sunk.

[7.11] Passenger Delivery

This mission requires the delivery of a VIP passenger to a given location (either New Guinea or India). To do so, the submarine travels to the first track box assigned in its area. On arrival, a roll is made in the Special Missions section of Encounter Table [A3]. If no aircraft appears, it is assumed that the passenger has been landed successfully by rubber boat. If an encounter occurs, it is resolved and the roll is repeated until the area is clear and the passenger can be landed. After landing, the rest of the patrol is carried out normally and the mission is considered a success. If the passenger is killed or seriously wounded before landing, the mission fails. The passenger counts as a pilot on the Crew Wounds Table.

[7.12] Removal of Deck Gun/Aviation and Access to Kaiten

As the war progressed, the Japanese took desperate measures to change the course of events. One of these measures was the installation of "Kaiten" suicide manned torpedoes on the decks of some submarines, to release them near American ships in port, as a sort of "kamikaze" of manned torpedoes. To make room for them, certain classes had their deck guns and/or aviation removed. These classes have annotations on their Control Sheets indicating the date on which this occurs. Once removed, deck guns are not reinstalled, even if subsequent missions do not involve kaiten operations.

[7.13] Completion of Special Missions

A special mission completed successfully counts as two successful patrols for the improvement of the crew's level, whether or not any ship was sunk. Its failure denies the consideration of a successful patrol, even if sinkings had been achieved. This double credit for successfully completing special missions does not apply to the Kirai-Sen minelayer class, which carries out a minelaying mission on every patrol.

[7.14] Major Event Markers

There are 27 Major Event markers for use during play. At the start of each patrol, the new markers that are active (by date) are placed on the map, and those that have expired are removed. The front of each Major Event presents the historical title (Pearl Harbor, Indian Ocean, Midway, etc.), together with the months and years in which the event is active. The reverse of the markers includes a list of one to three special missions available for that Major Event.

Submarines assigned to patrol an area with an active Major Event marker, instead of carrying out a normal patrol, will carry out one of the special missions mentioned above that appear on the reverse of the event marker. The special missions on the Major Event marker must be checked in order, and the first one on the list, from top to bottom, that the submarine is capable of carrying out is performed. It is possible that a submarine cannot carry out the special mission in question. For example, a "Midget Submarine Attack" mission on the list cannot be carried out by a class of submarine that does not carry a midget submarine. A special mission of "Bombing" cannot be carried out by a submarine that has no aviation, and so on. If none of the special missions listed on the reverse of the Major Event marker can be carried out by the current submarine, the event marker is ignored and the submarine carries out a normal patrol. However, some Major Event markers have a "Patrol" mission on the reverse. Although any submarine can carry these out, they still count as a special mission for the purpose of earning two successful patrols.

[7.15] Aircraft Launch and Recovery

Aircraft can be launched in the game from submarines equipped with a hangar (Types A, A (Modified), B, B.3, Junsen J.2, Junsen J.3 and Sen-Toku). They were stored disassembled in watertight hangars on the deck, to be assembled and launched afterwards. Normally, aircraft are launched and recovered in the same track box. However, several setbacks may prevent this:

The aircraft cannot be launched if its pilot is seriously wounded (SW) or killed in combat (KIA).
The aircraft cannot be launched if the hangar is damaged or inoperative. Each time a hangar suffers damage, the destruction of one of the submarine's aircraft is assumed (some Japanese submarines carried up to 3 aircraft). If the hangar is repaired, any surviving aircraft may then be launched.
A damaged or inoperative crane does not prevent the aircraft from being launched; it simply means the aircraft cannot be recovered.

Launching an aircraft requires a dice roll according to the Aviation Module, even if the submarine is not on a special mission and the aircraft is used only for reconnaissance tasks. An aircraft may be launched even when not on a special mission, for the purpose of reconnaissance. If this is done, an "additional" encounter roll is obtained for that track box. If, on the other hand, the encounter roll results in an aviation encounter and the submarine's own aircraft is in the air, it is automatically considered lost. Launch and recovery are not automatic; rolls are made on Tables [P1] and [P2] respectively, belonging to the Aviation Module.

[7.16] Midget Submarine Module

The module applies only if the submarine is equipped to carry a midget submarine and is assigned a midget submarine attack, as indicated on a Major Event marker.

If a midget submarine is carried, the Midget Submarine Training School, Table [F2], must be rolled for the midget submarine's commander before setting out on patrol. This is done on every patrol for which there is a new commander, in case the previous one was killed in combat.

There are 4 midget submarine attacks in the game: Pearl Harbor (M1), the port of Sydney (M2), Diego Suárez (M3, in Madagascar) and Guadalcanal (M4). When this mission is assigned, the submarine travels to the location of the Major Event marker in the normal way, making encounter rolls along the way.

At the location of the Major Event, play passes to one of the four harbour maps (Tables [M1 to M4]) and the game continues with the Midget Submarine Control Sheet. Note that the harbour maps have "travel circles" (as opposed to track boxes), which serve merely as a reminder that operations are now being conducted at a smaller scale.

Once the Major Event marker box is reached, the game continues according to the following sequence:

Place on the Midget Submarine Control Sheet two Type 97 torpedoes and any other applicable markers obtained from the training school. The midget submarine marker is also placed in Transit Box 1 on Tables [M1 to M4], as appropriate for the current mission.
Advance from box to box, making one roll on the Midget Submarine Encounter Table for each Transit Box (including the first) and once in the Target Box. Encounters in each box must be resolved before advancing to the next. In some harbours there are detector loops, which may cause an attack by escorts once passed, and/or anti-submarine nets (which may also cause an attack by escorts, or possibly trap the midget submarine).¹
Midget submarines have their own encounter tables for use in the Transit Boxes and the Target Boxes. Encounters in the Transit Boxes will sometimes require consulting the Midget Submarine Events Table [M6].
All midget submarine attacks are carried out submerged, regardless of whether it is day or night. In addition, midget submarines cannot use the game mechanic of exceeding the test depth. Otherwise, all attack and detection rolls are made using the standard rules of the game, with the exception that attacks against static naval targets (in the Target Box) are made with a DRM of -1 to hit on Table [B1], and a DRM of -1 to damage on Table [B3].
Once the encounters in the final Transit Box have been checked, roll 1d6 to recover the midget submarine. On a result of 1-3 it is considered lost; on a result of 4-6 it is considered recovered (consult Table [M7]).
After the recovery attempt, the player must return to his standard Control Sheet and to the Patrol Map to continue his patrol.

Note: the term "escorts" used above in the Midget Submarine Module technically refers to a variety of small anti-submarine warfare (ASW) vessels, but the term "escorts" is used in order to match the terminology of the combat rules of the main game and reduce confusion.

¹ Detector loops: submarine electric cables laid on the seabed at the entrances to harbours. When a metal submarine passed over them, it altered the magnetic field and gave an alarm signal at the shore base, alerting patrols to attack it.

[7.17] Aviation Module

This module applies only if the assigned submarine class is equipped with one or more aircraft on deck, disassembled and stored in watertight hangars. If so, the first step is to make a roll for the pilot or pilots to attend the Flight School (Table [F3]). This may give them special skills or abilities for use during missions. An aviation mission may take place if the submarine is assigned to an area with a Major Event marker and that marker has been assigned a special mission classed as Reconnaissance or Bombing. Once inside the Major Event box, the game continues according to the following sequence:

The Aviation Control Sheet is placed in front of the player, together with any other applicable markers obtained at the training school. The corresponding aviation marker is also placed in Transit Box 1, on Maps [P7] to [P12], as appropriate for the current mission (the numbers on the reverse of the Major Event markers for Bombing and Reconnaissance missions are linked to these maps).
Take-off is made by rolling 2d6. On a result of 2 or 12, a roll must be made on the Mishaps and Malfunctions Table [P1].
Advance from box to box, making an encounter roll in each one (beginning with Transit Box 1). The encounter results listed in the Transit, Reconnaissance or Target columns of Table [P3] must be used, as appropriate. An aircraft damaged by another aircraft or by anti-aircraft fire must abort the mission. In bombing missions, the bombing is executed in the Target Box using Table [P6].
After making the encounter roll in the final Transit Box (and resolving it, if necessary), the submarine's recovery roll on Table [P2] must be made. If the recovery fails, the crew and the aircraft are considered lost. If the submarine's crane is inoperative, the aircraft cannot be recovered; however, if the recovery roll succeeds in this case, the crew will be rescued (they are picked up from the water and the aircraft is left behind).
If the pilot is killed (or missing in combat), a new pilot must be generated through the Flight School the next time the submarine is at base, and a new aircraft is received. Rear gunners who are killed in combat or seriously wounded are replaced directly at base.
The Type A (Modified) class has two aircraft. For aviation operations with this class, the Flight School process must be carried out twice, and each pilot will be granted independent skills depending on the choices made. The same procedure applies to the Sen-Toku class with its three aircraft.

Terminology note: the abbreviation "A/C" stands for "aircraft" (aviación) where it appears in the rules or tables.

[7.18] Kaiten Module

Hard to translate, "kaiten" means "turning the sky", but here it is rendered as "the turning of the will of Heaven" or "the Sky Shaker". Kaiten were manned suicide torpedoes. Like "kamikaze" aircraft, kaiten were modified torpedoes with very large explosive warheads, guided to the target by a suicide operator. Several submarine classes were modified to routinely carry six units on deck, although some carried fewer. Although they promised good results on paper, kaiten were not very successful in practice. Being difficult to steer and operate, many suffered faults and mechanical problems, which sometimes caused launch failures and, more unpleasantly, premature detonations. A few penetrations into ports were successful but, in general, the programme was inefficient. Only the sinking or damage of 3 American ships by kaiten action was confirmed, at the cost of more than 100 kaiten pilots.

This module applies only if the submarine is equipped (or can be equipped) to carry kaiten, and is assigned a kaiten attack as indicated on a Major Event marker. There are five kaiten events in the game: three against the port of Ulithi (K2) and two considered in the open sea (K3) near Iwo Jima and Okinawa. When this mission is assigned, the submarine heads to the location of the Major Event marker in the normal way, making encounter rolls along the patrol track boxes. For each kaiten, the Otsujima Kaiten Training School, Table [F4], must be consulted, choosing one advantage for each pilot. The advantages chosen apply only to that pilot; they need not all be the same.

At the Major Event location, play passes to one of the two kaiten maps (Tables [K2] and [K3]) and the game continues with the Kaiten Control Sheet. Note that the kaiten maps have circular track boxes (in contrast to the square track boxes), which serve merely as a reminder to the player that he is now operating at a smaller scale.

Once inside the Major Event box, the game continues according to the following sequence:

The Kaiten Control Sheet and one of the two kaiten maps [K2] or [K3] must be at hand. Kaiten are launched one by one, rolling 1d6 (1-3 success, 4-6 mechanical failure). A check is then made for premature detonation: on a roll of 6 on 1d6, the kaiten explodes prematurely and is removed. Each kaiten that is successfully launched and survives the premature-detonation roll is placed in Transit Box 1.
Advance from box to box, making a roll on the Kaiten Encounter Table once for each Transit Box (including the first) and once in the Target Box. Encounters in each box must be resolved before advancing to the next. If attacking the port of Ulithi, each kaiten must roll to cross the atoll reef, succeeding on a result of 9 or more on 2d6. A failure results in the loss of the kaiten. This check must be made on arrival at the Target Box, before the encounter roll.
A detection roll by the escorts must be made on reaching the Target Box. If the kaiten is not detected, or survives any detection, the naval target is determined and the target is chosen. Any surviving kaiten makes a roll to hit. If it hits, a defective torpedo check must be made according to Table [B2]. Kaiten that explode inflict +2 additional damage points (for a total of between 3 and 6 points).

Note: the explosive warheads of the kaiten were significantly larger than those of the Type 93 Long Lance torpedoes on which they were based.

Once all kaiten have exploded or failed to launch, the mission is considered complete and play returns to the maps and tables of the main game. The player must then make a roll in the Additional Combat Round section of the main game's Encounter Table. After resolving any encounter, the submarine continues on its patrol route.

8.0 Combat

[8.1] General Procedures

[8.1.1] Combat rounds. Combat is resolved in each patrol track box in rounds, each round being made up of several turns. There may be additional combat rounds if the encounter is not completed in the first round. This is at the discretion of the commander; he is not obliged to keep tracking a damaged ship, for example.

[8.1.2] No encounter. If no encounter occurs in a patrol track box after consulting Table [A3], nothing happens. The submarine advances one patrol track box along the route and makes a new roll. Submarines equipped with radar have a second chance to obtain an encounter if the first roll was a "5", provided the radar is operational.

[8.1.3] Ship encounters. If a ship is obtained on the encounter roll, roll 1d6 to determine its size. This is the simplest encounter for the submarine, since it involves a ship sailing alone. A roll of 1-4 indicates a small ship. A roll of 5-6 indicates a large ship. The result "SHIP(S) + ESCORT" is also possible, in which case it is one or two single ships that have escort protection. Once the size has been determined, roll on the corresponding target table [T1] or [T2] to identify the exact ship or ships intercepted.

[8.1.4] Capital ship encounters. If a capital ship is obtained on the encounter roll, roll on Table [T4] to determine which ship it is. Those intercepted in the Dutch East Indies, Malaya, Indochina or the Indian Ocean are determined on the British sub-list. These encounters always have escorts. Unlike The Hunters, sinking any of them automatically awards the Order of the Golden Kite (4th or 5th class, depending on the commander's rank). Their escorts were normally very numerous and, consequently, receive a DRM of +1 on the detection table against the submarine.

Not all of them require 5 points of damage to be sunk; the largest battleships need 6 or 7. Additionally, like warships, some are "Fast Targets" because of their high speed, applying a DRM of +1 when torpedoes are fired at them. These have an indicator on their counter.

[8.1.5] Warship encounters. If a warship is obtained on the encounter roll, roll on Table [T3] (or on [T5] if in the Indian Ocean, Malaya, Indochina or the Dutch East Indies) to determine which warship it is. Warships are always considered escorted. All warships are considered "Fast Targets", meaning they are harder to hit because of their high speed, so a DRM of +1 applies to the hit roll when torpedoes are fired at them. In addition, destroyer escorts (DE), destroyers (DD) and generic escort targets receive an additional DRM of +1 to the hit roll when torpedoes are fired at them because of their small size. This modifier applies cumulatively with the +1 DRM for being Fast Targets.

[8.1.6] Convoy encounters. If a convoy is obtained on the encounter roll, three dice are rolled to determine the number of targets closest to the attack position. A roll is then made for each ship individually on the corresponding table to identify the exact vessel intercepted. Convoys are always considered escorted by active escorts.

Note: convoys had many more ships than a single submarine could attack. Therefore, only three of them are represented in the submarine's "window of opportunity" for that encounter.

[8.1.7] Aviation encounters. If aviation is obtained on the encounter roll, roll the die on Table [A4], applying the corresponding modifiers. These encounters are resolved as described in section (8.3).

[8.1.8] Random events. The first natural "12" obtained in a patrol track box does not generate the listed encounter, but a random event. Consult the random event table, roll the die again and resolve it. Only one random event is allowed per patrol; any subsequent "12" in a track box is resolved as the normal encounter indicated on the patrol table.

Note: at the start of the war, transit boxes do not generate encounters. However, the die must still be rolled to check whether a "12" is obtained, which would trigger a random event for that patrol.

[8.1.9] Time of day. Roll 1d6 to determine the time of day: a result of 1-3 indicates day; a result of 4-6 indicates night. Night surface attacks may only be carried out at night. During the day it is easier to spot the wakes of steam torpedoes; therefore a DRM of +1 to detection applies to such attacks.

[8.1.10] Changing between day and night. If one wishes to engage a daytime contact after obtaining a "night" result (or vice versa), the change may be made, assuming a small risk of losing the contact. Roll 1d6: a result of 1-4 is a success. On a result of 5-6 the contact with the target is lost (ending the encounter in that patrol track box).

[8.2] Ship Encounters: Attacks against Naval Targets

Once the time of day and the targets have been determined, the submarine's commander must decide how to proceed with the attack.

[8.2.1] Choice of range. The range of the attack is chosen. Each range has advantages and disadvantages. At medium or long range, fire is opened first, but with a lower probability of a hit. At short range, a detection roll must first be made on Table [B4]; to avoid detection one must roll "9" or less on 2d6. If the commander holds the Order of the Golden Kite, a DRM of -1 applies. Without prior detection, fire priority is maintained. If detected, the submarine cannot attack and suffers a counterattack on Table [B5]. Unescorted ships have no detection, so there is no short-range penalty in that situation.

[8.2.2] Night attacks. If the encounter occurs at night, one must also decide whether to carry out a night surface attack.

Although this permits slightly better torpedo calculations, owing to the use of the conning-tower optics, a DRM of +1 applies to the detection roll. This represents the growing availability of Allied surface radar. A night surface attack also suffers a DRM of +1 on Table [B5] during the first round, and the submarine cannot exceed the test depth in that round, since it is, in essence, still too close to the surface at that moment.

A submarine may launch a "second salvo" from the other end of its hull when carrying out a night surface attack. However, these torpedoes are fired with a DRM of +1 to hit. For example, all torpedo tubes may be fired against a convoy, firing the first salvo normally (usually the bow tubes) and the stern tubes with a DRM of +1 to hit (in addition to any other DRM to hit).

Historical note: second salvos were not feasible while submerged, since the submarine would take too long to turn 180 degrees under water. For this reason, they are only permitted when carrying out a surface attack.

[8.2.3] Attack procedure. One or all of the bow or stern torpedoes may be fired against any target, but all must come from the same end of the submarine (unless a "second salvo" is fired (8.2.2)). All shots are declared before the rolls are made; a roll is then made to check whether the torpedoes hit. After a hit, a roll is made to determine which torpedoes are defective, on Table [B2]. ("Defective" is used to represent any malfunction that causes the torpedo not to explode or to detonate prematurely. Although fairly reliable, torpedoes were still at times an imperfect weapon.) For any torpedo that hits and is not defective, a further roll is made to determine the damage inflicted on Table [B6]. A variable amount of damage, depending on the size of the ship, is required to sink it.

NOTE: all capital ships (regardless of their actual tonnage) require 5 to 7 points of damage to be sunk, as indicated for each ship.

[8.2.4] Deck gun fire. In addition to firing torpedoes in the first turn of combat, the submarine may fire two deck gun shots per available deck gun against unescorted ships (each "shot" of deck gun actually represents about 25 shells in real life). Note that deck gun ammunition is limited per patrol. The results of deck gun fire may be evaluated before the next shot (one shot at a time, as needed or as desired).

[8.2.5] Escort detection. After the first torpedo salvo against escorted ships, a roll is made for the escorts on Table [B4] to attempt to locate and attack the submarine. If it remains undetected, the combat turn ends.

If detected, the submarine immediately suffers an attack on Table [B5]. For each "hit" obtained on Table [B5], a roll is made on it to determine the depth-charge damage. Once the damage has been applied to the submarine, and after checking whether additional flooding occurs on Table [B6], the cycle continues. A detection roll must be made again, applying the "+1" DRM for prior detection and any new DRMs, such as those for damage to the diving planes or fuel tanks. If detected again, another roll is made on Table [B5]. The rounds continue with the detection and attack process until the submarine escapes on Table [B4] or is sunk. Evading detection is harder in the later rounds if a large amount of damage has been suffered.

In Sensuikan, each attack cycle may involve a "special attack" instead of a normal one. From May 1944, before the escorts' attack, 1d6 is rolled. On a result of 1-5, the normal attack is carried out. On a result of 6, a "special attack" occurs instead, which is resolved in the "Hedgehog" section of Table [B5]. This does not occur more than once per encounter.

Although the submarine may "sneak in" at short range on obtaining a "9" or less on detection, all rolls after the start of combat are made with a DRM of +1 if at short range. This approach against escorts is extremely dangerous in the final stages of the war, and must be undertaken with caution.

[8.2.6] Exceeding test depth. Submarines may attempt to evade escorts by exceeding the test depth, but this is considered a risky procedure. Before making the escorts' detection roll on Table [B4], one must decide whether to attempt to increase the chances of escaping by exceeding the test depth and diving deeper than is safe. The submarine automatically suffers one point of hull damage, and 2d6 is rolled. If the result of the roll is less than the current number of hull damage boxes, the submarine implodes and sinks. If the result equals the number of hull damage boxes, one additional point of hull damage is suffered and the roll is made again immediately. (If there is only a single hull damage box, the roll must still be made, even though implosion is impossible at that moment. In that case, if a "2" is obtained, another hull damage box is suffered and the roll is made again immediately.) If the result is greater than the current number of hull damage boxes, no effect occurs and the escorts' detection roll receives a DRM of -1. The submarine must suffer additional hull damage and roll for each combat round in which it wants a DRM of -1. Test depth cannot be exceeded in the first turn following a night surface attack.

Designer's note: taking the submarine deeper than it was designed for is obviously dangerous if significant hull damage has already been suffered. However, there may be situations in which there is still little or no hull damage, but fuel tanks have leaked, batteries have been damaged, etc. In such a case, the use of this option might be considered; although some players may think they can abuse this rule by using it frequently, the mandatory hull damage means that one will always be in maintenance and refit for at least one additional month per patrol, which will reduce the time at sea in the long term.

[8.2.7] Automatic evasion. Regardless of how unfavourable the DRMs for the detection cycle, a natural "2" ("snake eyes") always results in "not detected", and the submarine evades.

[8.2.8] Additional combat rounds. If for any reason an unescorted target has not sunk (or the torpedoes missed), one may choose to start an additional combat round, reloading the torpedo tubes if desired, and rolling on Table [A3] under the "Additional combat round" section.

If no escorts or aviation arrive, one may fire torpedoes again, or carry out up to 2 deck gun shots from short range, according to the normal combat procedure.
If an escort arrives, a detection roll must be made immediately on Table [B4].
If not detected, one may attack under the normal rules and make a new detection roll after the attack; in essence, the process is starting from scratch against the target, which is now escorted.
If detected, one cannot attack and is subjected to the normal escort attack procedure.
If the result indicates the arrival of aviation, the attack must be aborted, an immediate dive made, and a roll made under the aviation encounter rules.

Up to two additional combat rounds may be carried out in the same track box. If a third additional round is required (or desired), one must first advance to the next track box and then continue. The same applies to each subsequent box (only 3 combat rounds in total per box), although such a situation would be extremely rare. This action cannot be taken in the last non-transit track box, since one must set course for port at that point because of fuel limits.

No additional combat rounds are permitted against escorted ships once a combat round has been completed. Instead, one may choose to attempt to sink any ship using the "tracking" mechanic. (In short: additional combat rounds are used against unescorted targets, while "tracking" is used against escorted targets.)

[8.2.9] Special Procedure for Encounters with Enemy Submarines

[8.2.9.1] Initiative roll. The enemy submarine has a high probability of attacking first. Roll 1d10. On a result of 1-3, the player's submarine gains the initiative and may attack or avoid contact. On a result of 4-10, the enemy submarine has detected the position and attacks first, firing four torpedoes at the player's submarine. This attack is made from medium range. Then a roll is made for an additional combat round, or contact is broken, according to (8.2.9.4). After this "surprise attack" by the enemy submarine, the player's submarine, if it has survived, may return fire in any subsequent combat round. Note that the range will be medium in this case. It may also withdraw, and the encounter ends.

[8.2.9.2] The player attacks first. If the player's submarine attacks first, the usual procedure is followed: one must decide whether to attack from medium or long range, or whether to risk a detection roll to approach at short range. Enemy submarines cannot be attacked with the deck gun. Note that an enemy submarine is harder to hit, since it receives the "+1" DRM for warships when torpedoes are fired at it. If detected while attempting to approach at short range, the attack is aborted and the enemy submarine attacks first from short range. If the player's submarine has the initiative (a roll of 1-3 on 1d10), it may also simply reject combat, and the encounter ends.

[8.2.9.3] The player sinks the enemy submarine. If the enemy submarine is sunk in the first combat round, the encounter ends without requiring any further action. Only 1 point of damage is required, so any non-defective hit sinks the submarine.

[8.2.9.4] The player fails to attack the enemy submarine. If the attack against the enemy submarine fails, the enemy submarine makes a detection roll applying the corresponding DRMs. If detected, the enemy submarine fires four torpedoes at the player's submarine, hitting on a result of 2-4 at short range, 2-3 at medium range, or 2 at long range (2d6). Enemy submarine torpedoes are defective on a roll of "1". Any non-defective torpedo hit by the enemy submarine will sink the player's submarine. At this point, assuming the enemy submarine has not sunk the player's own, there is the option of rolling for an additional combat round or breaking contact. If contact is broken, the turn ends and one advances to the next track box. If an additional combat round is chosen, the tubes are reloaded and an encounter roll is made; a result of aviation or escort means the enemy submarine escapes (and the new threat must be dealt with). If no aviation or escort arrives, a new combat round is then started from scratch against the enemy submarine.

[8.2.10] The Combat Sheet. The Combat Sheet (Table [H1]) is provided to assist during combat against ships and convoys, if desired. Its use is not mandatory, but it can be useful for tracking which torpedoes are heading towards each target, etc.

[8.2.11] Combat against escorts. Unlike the war in the Atlantic, combat against escorts (or warships in general) occurred more regularly in the Pacific, for various reasons. To represent this, it is permitted (but not required) to attack an escort accompanying the target ship or ships.

To attack an escort, a generic escort target (2,000 tons) is added. This ship is now added to the other target ships available and is attacked normally under the attack rules. (Although there may be more than one escort, just as there are more than four cargo ships in a convoy, it is assumed that only one will be within the "window of opportunity" for the attack at the start.) Escorts are significantly faster and smaller than cargo ships, so they receive a DRM of +2 on torpedo hit rolls (+1 for being fast and +1 for being small, for a total of +2; this is the same DRM given to the DD and DE warship targets).

[8.2.12] Sinking an escort. If the escort is sunk, detection rolls for the rest of the combat are made with a DRM of -1 (and, of course, credit is received for that escort's tonnage). If the escort survives the salvo, even if damaged, detection rolls are made with a DRM of +1 for the rest of the combat. If the optional escort quality rules are used, the escort's quality is not rolled again. If it was only damaged, the escort can still be attacked at a later time.

Designer's note: although this may seem a very advantageous option, it should be noted that several torpedoes will (probably) be spent on a ship of extremely small tonnage, and they may not even hit, owing to the built-in +2 DRM to hit a small, fast warship. One should think twice before attacking escorts on one's own initiative. It may be better to deal with the depth-charge attack, because if the escort is not sunk or damaged, it will counterattack with an additional DRM of +1 on the detection roll.

[8.3] Aviation Encounters

[8.3.1] Quick dive roll. Once an aviation encounter is obtained, a roll is made to determine whether combat occurs, on Table [A4], rolling 2d6 and applying the corresponding DRMs. If the modified result is "6" or higher, no combat occurs. The aircraft was sighted in time, the submarine makes a quick dive, and nothing further happens.

[8.3.2] Aviation attack. If the modified result is 5 or less, one (or possibly two) attacks are made on Table [B5], applying a DRM of "+2" per aviation attack (for a normal attack). From May 1944, 1d6 is rolled to check whether a "special" attack occurs instead of the normal one. On a result of "6", the special attack is carried out, assuming that the aircraft was equipped with a special attack weapon (see 8.3.3). Damage is applied (or the submarine is sunk outright). Likewise, a crew casualty roll is made in addition to any other damage caused (except in special attacks). The submarine may fire its anti-aircraft weapons. Combat is considered simultaneous, so a submarine may shoot down the aircraft that is sinking it (as happened historically). The following results are determined according to the anti-aircraft fire against the aviation:

Aircraft shot down: the second attack does not occur (if a modified result of "1" was obtained on Table [A4]). No further actions are taken in this track box, except possible repairs.
Aircraft only damaged: the second attack does occur (if a modified "1" was obtained on [A4]). However, no further actions are taken in this track box apart from possible repairs; the damaged aircraft must immediately return to its base, concluding the encounter.
Aircraft suffers no damage from anti-aircraft fire: it will shadow the submarine after completing its own attack. The submarine is considered to have dived at this point. Roll in the "Additional combat round" section of the Encounter Table [A3]. This may result in the arrival of an escort, which will roll for detection on Table [B4] (from medium range), or the appearance of new aviation, which will attack by means of Table [B5]. Note that an aviation attack may chain into another aviation attack in succession if an unfavourable run of rolls on Table [A3] occurs. The escorts must roll to detect the submarine, but they receive the +1 DRM for "prior detection". However, new aviation generated by the "Additional combat round" table goes directly to the attack section and hits the submarine.

Note: aircraft following the first one do not cause an automatic crew casualty, since the submarine is considered already submerged. After resolving all combat, the submarine advances one track box in its patrol.

Editorial note: in the source text, the paragraphs on the outcomes of anti-aircraft fire and the historical note on the FIDO table each appear twice with minor wording differences ("Tabla de combate [A4]" / "hoja de combate [A4]"; a repeated sentence fragment). They are transcribed here once; the wording is otherwise unchanged.

[8.3.3] Special FIDO aviation attacks. Acoustic-homing FIDO torpedoes allow aviation to attack without causing automatic crew casualties, but a direct hit results in automatic sinking or 7 hits to the submarine. This mechanic equates the special capability of escorts with Hedgehog torpedoes. For more information, see the Sensuikan rules.

Historical note: players may think the FIDO combat table underestimates its effectiveness. It does not, since it is based on historical results. When one takes into account the fact that this is a first-generation homing torpedo, the results make more sense.

[8.3.4] "Hounded to exhaustion". If any combination of aviation or escorts occurs four times consecutively within the additional combat round cycle, the submarine is considered to have been "hounded to exhaustion". With almost no oxygen and little remaining battery power, it must surface and scuttle the vessel.

[8.3.5] Specific DRMs for anti-aircraft artillery. Many submarines had two or more anti-aircraft guns; therefore, if at least two of them remain operational, a DRM of "-1" applies to hit. If one has been put out of service, fire is made without that modifier. Obviously, if a submarine has all of its anti-aircraft guns inoperative, it cannot fire against aircraft. Deck guns cannot fire against aircraft. For game purposes, anti-aircraft ammunition is unlimited. Submarines did not usually "stay and fight" on the surface against aircraft; if they had the misfortune of having to fire their anti-aircraft guns, it is considered that they dive immediately afterwards. Twin and triple 25 mm mounts count as a single system (gun) for the purposes of Table [A2].

[8.4] "Tracking" a Convoy or Ship

[8.4.1] General rule. Once all combat in a round has been concluded, the player advances the submarine marker one track box along the corresponding patrol route. However, if one wishes to continue attacking a convoy or escorted ship, one may remain in the same track box and attempt to track it.

[8.4.2] Tracking damaged ships. Tracking is automatic if any escorted ship was previously damaged but not sunk. If the ship was escorted, it is considered to remain escorted with a result of 1-4 on 1d6, applying the normal combat rules, and the ship keeps its previous damage. With a result of 5-6, the ship becomes an unescorted "straggler". If tracking was of two (or more) ships and a 5 or 6 is obtained, they become unescorted but "scatter", and one must choose which to pursue.

If the tracking is of a damaged escort (or other ship), it becomes another naval target. The escort itself remains escorted with a result of 1-5 on 1d6, like any other damaged ship. If it is not escorted, it may be attacked, but not with the deck gun, and only while submerged and using torpedoes (never the deck gun).

If the damaged ship is a capital ship, tracking is not automatic, since they were quite fast. In the game it depends on the amount of damage inflicted, since it is assumed that greater damage will reduce the speed of the ship to the point of allowing it to be caught. Roll 1d6. A modified result of "1" means that tracking of the capital ship has been successfully carried out. This die roll has a DRM of -1 for each point of damage the capital ship has, and a DRM of -1 if radar is operational.

Example: 2 points of damage are inflicted on a capital ship. To track and attack it again, apply a DRM of -2 for the damage, succeeding on a result of 1-3.

[8.4.3] "Stragglers". If one or more ships formed part of a convoy and were damaged according to (8.4.2) above, they are considered to "stay together" if escorted (rolling 1-5 on 1d6), but they become independent stragglers if unescorted (rolling 6 on 1d6). If they separate, one must choose which of them to finish off. If they are together but still escorted, one may attack any or all of them under a normal encounter, except that they are already damaged. If one decides to attack the previously damaged ship(s), one loses contact with the original convoy and cannot track it again. The decision may be profitable, depending on the situation of the submarine (whether or not it is damaged), to attempt to track the convoy instead of opting for the automatic tracking of a single damaged ship.

[8.4.4] Tracking a convoy. If only a convoy (or two escorted ships) is to be tracked, tracking is attempted with a roll of 1d6. A result of 1-4 succeeds, and the convoy may be attacked as if a convoy had been obtained on the Encounter Table [A3]. A result of 5-6 means that the convoy or ships have escaped, and the round ends. The submarine marker is advanced one track box and the patrol continues. Having an operational radar gives a DRM of -1 to the tracking die roll.

Note: a bird in the hand is worth two in the bush, so to speak. It is almost always advantageous to try to track a convoy unless one firmly desires some other type of encounter. Since convoys are automatically escorted, having a seriously damaged submarine may influence this decision.

[8.4.5] Multiple tracking attempts. A convoy or escorted ship(s) may be tracked up to 2 times (for a total of 3 attack rounds) during the same track box. If one wishes to track the convoy or ship again, the submarine marker is advanced one track box and tracking is attempted by the normal procedure, instead of making the usual encounter roll for that track box. If this is unsuccessful, no other encounters occur in that track box. Tracking cannot be carried out into a transit box, since at that point one must head for port because of fuel limits.

[8.5] Damage to the Submarine

[8.5.1] General rule. Submarines will receive non-lethal damage in the course of operations, which can possibly be repaired at sea. In addition, damage has effects on combat as indicated in Table [B7]. Further explanations of those effects are detailed below.

[8.5.2] Repair after combat. At the end of a combat (not a combat turn), the submarine's crew, under the direction of the engineer, may attempt to repair any damage the submarine has received. A roll is made to repair all damaged systems except the hull. All "DMG" (damaged) markers are removed from the equipment or systems that have been repaired. For any item that fails the repair roll, the "DMG" markers are turned over to their "INOP" (inoperative) faces. If the engineer is an "expert", all rolls are made with a DRM of "-1". If the engineer is dead or seriously wounded, the repair rolls are then made with a DRM of "+1".

[8.5.3] Flooding. During combat, at the end of each turn, the submarine checks for additional flooding only if it has received one or more flooding damage boxes in that turn.

There is no need to check whether, for example, flooding occurred three combat turns earlier. With a result of 5-6 on 1d6, one additional point of flooding damage is received. If the engineer is an "expert", all rolls are made with a DRM of "-1". If the engineer is dead or seriously wounded, all additional flooding rolls are made with a DRM of "+1".

If all flooding boxes are full, the submarine must blow ballast, surface immediately and make a scuttling roll. Unlike other types of damage, all partial flooding is completely removed, without rolling the die, once combat is complete, provided the submarine survives. It is assumed that the water is pumped out by the bilge pumps.

[8.5.4] Engines. Electric motors are used when submerged; diesel engines are used on the surface. If a diesel engine fails, the submarine must abort the mission and make two encounter rolls for each track box on its return route to base. If both diesel engines become inoperative, the submarine will be towed to base if it is one track box away from it; otherwise it is scuttled, and the crew makes a rescue roll. The loss of the electric motors has serious effects in combat, as detailed in Tables [B5] and [H1].

[8.5.5] Hull. Hull damage cannot be repaired at sea. If the submarine has all of its hull damage boxes marked with the damage marker, it is considered sunk with the loss of the entire crew. On return to base, every three hull damage markers (or fraction thereof) add one month of maintenance and refit before the next patrol can begin. This is added to any normal maintenance and refit time.

[8.5.6] Fuel tanks. If the fuel tanks are damaged and fail the repair roll, the submarine must abort the mission immediately at the end of combat. Significant combat penalties also apply, since the submarine is easier to detect.

Note: having the fuel tanks in the "INOP" state does not mean that they do not function or are empty. Rather, it means that the leak could not be repaired and will continue to lose fuel for the rest of the patrol.

[8.5.7] Batteries. Having damaged batteries has negative effects, as detailed in Table [B5].

Note: having the batteries in the "INOP" state means that they have suffered significant damage that cannot be repaired, and that they will not function at full capacity for the rest of the patrol. It does not mean that they are completely exhausted or useless.

[8.5.8] Radar. Having an operational radar set gives benefits when changing between day and night, when tracking, and in encounter rolls. If it becomes inoperative, those benefits are lost.

[8.5.9] Crew casualties. Japanese submarine crews numbered approximately 100 men, with variations according to the type of vessel. The game tracks five specialist crew members, the generic crew and, if any, the pilots of the aircraft and the midget submarine crew. There are three possible results from crew casualties: lightly wounded (LW), seriously wounded (SW) and killed in combat (KIA). If the result is SW or KIA, the crew member cannot perform his functions, with the following results:

Captain: the executive officer (Exec) assumes command of the submarine. Torpedo/gun hit rolls suffer a DRM of +1, and escort detection rolls suffer a DRM of +1. Additionally, if he is seriously wounded (SW), he must remain at base for 1d6 months while recovering. This time runs concurrently with the submarine's maintenance and refit.
Executive officer (Exec): no effect, unless he was in command. If so, the navigation officer (NAV) assumes command of the submarine. Torpedo/gun hit rolls suffer a DRM of +2, and escort detection rolls suffer a DRM of +2.
Navigation officer (NAV): no effect, unless he was in command. In that case, the engineer assumes command of the submarine, and it must immediately abort and return to base.
Doctor: if incapacitated, all crew members with serious wounds (SW) have a chance of becoming KIA. A 1d6 roll must be made at the start of each track box: on 1-3 the crew member survives; on 4-6 he dies from his wounds. If the doctor is not incapacitated, no survival rolls are required for crew members with serious wounds (SW).
Engineer: repair rolls are made with a DRM of +1, including additional flooding rolls during combat.
Crew: no effect. However, if all generic "crew" boxes are marked SW or KIA, aviation encounter rolls on Table [A1] are made with a DRM of -1. This represents the additional difficulty the submarine would have in diving when operating short-handed. Unwounded crew members receive wounds before second wounds are applied to crew members previously wounded, and those with light wounds (LW) receive second wounds before crew members with serious wounds (SW).
Pilot: the pilot or pilots fly the aircraft carried on the submarine. If they are in the SW or KIA state, they cannot fly them. Multiple wounds are handled according to Table [B7]. However, a light wound (LW) has no effect on a crew member who is already seriously wounded (SW).

[8.5.9.1] Duration of wounds. For serious wounds (SW), 1d6 is rolled to determine the months of recovery for any crew member, once returning to base. If that time is greater than the current required maintenance and refit, that crew member is replaced (and all special benefits he may have had are lost). If all generic "crew" members are replaced after a single patrol, whether because of prolonged wounds or because they are KIA, crew quality drops one level (to a minimum of "Trained"). If the captain is incapacitated and this period is longer than the maintenance and refit time, his submarine will be assigned to another captain, and he will receive a new submarine of his choice when he is discharged. It should be borne in mind that this means any skills his former crew had acquired will be lost. However, the player may make a roll on the Submarine School Table [F1] to obtain his new executive officer (XO) and engineer.

[8.5.9.2] Crew casualties under depth charges. If depth-charge damage causes a crew casualty, it is automatically a light wound (LW). A roll is simply made to determine who is affected. However, these wounds accumulate and may eventually cause serious wounds (SW).

[8.5.9.3] Effects of an expert doctor. If the doctor has the expert upgrade, a roll is allowed for each light wound (LW) among the crew after an encounter. A result of "1-3" on 1d6 eliminates the LW. Additionally, an expert doctor reduces the recovery time of crew members with serious wounds (SW) by 1 month, representing the reduction of convalescence time due to the care received during the return voyage to base.

[8.5.10] Multiple damage results. If the table indicates damage to a system that is already damaged (or that is not present, such as a hangar hit on a Type C class submarine), it is treated as "no effect". The only submarine damage that "accumulates" is flooding and hull damage (and, as an exception, battery hits on a Sen-Taka class submarine). Note that a second "AA gun" result will damage the second anti-aircraft gun if two are present.

[8.5.11] Maintenance and refit rules. Submarines always have a minimum maintenance and refit time of one month. This means that if a submarine makes a one-month patrol in July 1943 and suffers no damage, August 1943 is considered a maintenance and refit month, and the next patrol will be in September 1943. Various events may extend this maintenance and refit process:

[8.5.11.1] Additional maintenance and refit due to damage. Any type of damage other than hull damage that has not been repaired on return to base is repaired "for free", up to a maximum of 2 systems. If 3 or more systems (boxes) are in the INOP state on return, this adds one month. This extra maintenance and refit time will not exceed one month; any number of damaged systems above 2 still adds only one extra month. Crew wounds are not counted for this rule.

[8.5.11.2] Additional maintenance and refit due to hull damage. For every 3 hull damage boxes (or fraction thereof), one month of maintenance and refit is added. For example, if a submarine returns with its periscope, fuel tanks, diving planes and 5 hull damage boxes damaged, it will require 4 months: one base month, one for the damaged systems (as it exceeds 2 systems), and 2 additional months for the hull damage.

[8.5.11.3] Variable patrol duration and "P" months. Different Japanese submarine classes had patrol durations of from 1 to 4 months. Each Control Sheet details the duration of that class if it exceeds one month. For each month after the first, a "P" (patrol) is written on the Patrol Log upon returning to base, before placing the "R" months of maintenance and refit. Because the patrols are longer, the "P" indicates that the submarine is still at sea that month. For example, if a patrol for a Type A class (2 months) starts in September, a "P" (still on patrol) is written in October and an "R" (maintenance and refit) in November. The submarine would set out again in December if it had suffered no damage.

[8.6] Cancelling a Patrol

[8.6.1] General rule. Certain damage will force the submarine to abort the mission and return to base (damaged fuel tanks or a diesel engine out of service). A submarine may always abort the patrol by order of the captain. This may be for any reason the captain considers, although usually it is because of significant damage or a shortage of torpedoes.

[8.6.2] Abort procedure. To abort, the submarine heads for base from the nearest transit box after combat and makes encounter rolls normally, which may require moving in reverse along its route. If it has a diesel engine out of service, it makes two encounter rolls per patrol track box. Submarines that abort cannot initiate combat, but may be attacked if detected by ships or aviation, continuing towards base or being sunk. If a class with 2-month patrols aborts before halfway along its route, no "P" is written on the Patrol Log (as it was out for only one month or a fraction of one). This procedure applies to 3- and 4-month patrols: the actual time at sea is calculated to the nearest month and rounded down.

[8.6.3] Scuttling the submarine. In some situations, the crew may be required to scuttle its submarine. If all flooding boxes have flooding markers in them, the crew must surface immediately and attempt to scuttle the submarine with a 2d6 roll:

2d6 roll	Result of scuttling
2-11	Success. The crew is captured and becomes prisoners of war (POW).
12	Failure. Submarine captured.

+1 to the roll if the captain is in the SW or KIA state.

A submarine with both diesel engines inoperative must also scuttle if it is more than one sea zone away from base, but this is automatic if it is out of combat. A 2d6 roll must be made for the rescue of the crew:

2d6 roll	Result of rescue
2-10	Success. Rescued.
11-12	Failure. Lost at sea.

+4 to the roll if the radio is inoperative.

[8.7] Crew Skills and Improvements

[8.7.1] Procedure. The various crew members, including the captain, may increase their skills during the course of the war. The general level of the crew may also increase. For every 3 successful war patrols, one option must be chosen from the table below. (A successful patrol is defined as one in which the submarine returned to base and at least one ship was sunk, or a special mission was successfully completed.) A marker must be placed in the specific crew position on the Submarine Control Sheet.

Effects of skills

Crew member / skill	Effect
Engineer: Expert	-1 DRM on a repair roll.
Engineer: Mechanical genius	Can repair a system that failed its repair roll and is currently inoperative (INOP). Usable only once per patrol.
Doctor: Expert	Roll 1d6 once to reduce a Light Wound (LW) to none; succeeds on a 1-3. Also applies a DRM of -1 to the die roll for a Serious Wound (SW), for each month of incapacitation.
Second officer (XO): Expert	No penalty when in command; -1 DRM on surface torpedo hit rolls.
Lookout (XO)	+1 on Table [A4] Aviation encounters.
Gunner: Expert (XO)	-1 on deck gun hit rolls on Table [B1].
Anti-aircraft gun expert (XO)	-1 on the AA Table [A2].
Navigation officer: Expert	The "Run Aground" event has no effect. The submarine need not abort if the navigation officer is in command. The submarine gains 1 extra track box per patrol if desired. Re-roll encounters in any track box (other than a transit box).
Captain: Shibumi (Mastery)	Difficult to translate; it may be understood as "effortless perfection". Once per patrol, the captain may pass a dice test without rolling. It may be used for a torpedo hit roll, the defective-torpedo check, the emergency dive, the sighting from an aircraft on Table [A4], and for a test-depth check.

*The crew quality levels are: Green (Novata), Trained (Entrenada), Veteran (Veterana) and Elite (Élite).

[8.7.2] Crew levels. The submarine's crew begins at the level of "Trained". If one chooses to improve it, the level rises to "Veteran". The veteran crew fires anti-aircraft guns with a DRM of -1 against aircraft on Table [A2]. A veteran crew may be promoted to "Elite". The elite crew fires anti-aircraft guns with a DRM of -1 on Table [A2], and additionally adds a DRM of +1 to the emergency dive rolls in aviation encounters on Table [A4]. The crew cannot be promoted above "Elite" nor drop below "Green". The "Green" crew has a DRM of +1 to hit with all weapons, and receives a DRM of -1 on aviation encounter rolls on Table [A4].

[8.7.3] Decrease in crew level. If all generic crew markers receive serious wounds or are killed in combat (KIA) during a patrol, the crew quality level drops one level (if above "Trained"). If a submarine has 3 consecutive unsuccessful patrols, the crew level drops by one (possibly down to "Green").

[8.7.4] Promotion of an expert executive officer. At the end of each patrol, 2d6 is rolled if the executive officer is an expert. A result of 2-3 indicates that he has been assigned his own submarine and must be replaced by a new executive officer.

[8.8] Decorations

The game includes a series of decorations for Japanese submarine commanders of the Second World War. Except for the Order of the Golden Kite, the decorations have no impact on play and are included for historical interest.

[8.8.1] Order of the Golden Kite (Kinshi Kunshō), 4th class. Highly coveted, this was awarded to successful submarine commanders for their valour in the performance of duty (the 4th class may be considered equivalent to the US Navy Cross). In the game, it is awarded to commanders for having sunk a capital ship, or after a patrol in which their tonnage exceeds 50,000 tons. Players who hold the Order of the Golden Kite receive a DRM of -1 on all detection rolls (not cumulative with the 5th class decoration). This decoration is only awarded to commanders of senior officer rank (commander and captain). If the player already holds the Order of the Golden Kite, 5th class, obtained when he was a lieutenant commander, the award criterion for the 4th class decoration becomes 100,000 tons or a capital ship.

[8.8.2] Order of the Golden Kite (Kinshi Kunshō), 5th class. Awarded to successful submarine commanders for their valour in the performance of duty (the 5th class may be considered equivalent to the US Silver Star). In the game, it is awarded to commanders for having sunk a capital ship, or after a patrol in which their tonnage exceeds 50,000 tons. Players who hold it receive a "-1" DRM on all detection rolls (not cumulative with the 4th class decoration). This decoration is only awarded to commanders of lower officer rank (lieutenant commander).

[8.8.3] Order of the Rising Sun (Kyokujitsu-shō), 8th class. A decoration for meritorious service. Received after the second year of service (24 months in the game).

[8.8.4] Order of the Sacred Treasure (Zuihō-shō), 8th class. Another decoration for service. Received after 12 months of service.

[8.8.5] Wound Badge (Shōigunjinshō). Awarded after being wounded on patrol. It may be received posthumously.

[8.8.6] Greater East Asia War Medal (Daitōa Sensō Jūgun Kishō). [2] Awarded after the first patrol (whether successful or not).

[8.8.7] Submarine Badge (Kaigun Sensuikan Shūgyō Kishō). Awarded on graduating from the Submarine School at the start of the game.

[2] Established 21 June 1944. It was a "ghost" decoration: it was manufactured in a limited number. Japan's imminent defeat prevented its official award before the surrender.

[8.9] Promotions

The captain of the submarine was the "commander"; however, his rank varied. At higher ranks, commanders have greater influence over submarine command, which has several positive effects on play.

[8.9.1] Ranks. The ranks and their associated abilities are:

Lieutenant Commander (Kaigun Shōsa). The lowest possible starting rank for the player. No special abilities.
Commander (Kaigun Chūsa). Allows a specific patrol to be requested with a result of "1" on 1d6. If this occurs, one may choose the next patrol area from the list active at that time on Table [A1]. If the roll fails (with a result of 2-6), one proceeds to roll normally for a random assignment. It should be borne in mind that this is voluntary; the player is not required to attempt to choose a specific patrol.
Captain (Kaigun Taisa). Allows a specific patrol to be requested with a result of 1-2 on 1d6, using the same procedure as above. It also allows any repair time between patrols to be shortened by one month, provided it is 3 months or more (it has no effect on repairs of 1 or 2 months). This represents his greater influence and ability to manipulate the system in order to obtain faster repairs.

[8.9.2] Promotion mechanics. Each promotion attempt is made after month 12 of service and every 12 months thereafter. For example, a player who began in 12/41 would make his first promotion roll in 12/42, and again every December. Failing a promotion roll simply means remaining at the current rank and waiting until the next period for a new consideration. Each successful promotion grants the player a submarine upgrade marker (see 9.3).

Promotion to the next higher rank occurs with a successful result of 1-4 on 1d6, applying the following DRMs:

-1: for the award of the Order of the Golden Kite (any class) during the period.
-1: for sinking 5 ships during the period.
+1: for each unsuccessful patrol during the period.

Multiple positive or negative DRMs may accumulate, depending on the course of the year. For example, it is possible to have a DRM of +3 due to three bad patrols in that year; in that case, promotion would be quite unlikely.

Commanders with the "Leadership" skill do not make promotion rolls. They are promoted automatically at each attempt.

[8.9.3] Starting rank. The game begins with the player as a lieutenant commander.

[8.9.4] Rank requirements for upgrades. The player must hold the rank of commander or higher in order to request a more advanced model, such as the Type A (Modified) or a Sen-Toku class.

9.0 Reassignment to a New Submarine

Reassignment to a newer submarine model may be received under certain circumstances:

[9.1] Reassignment Due to Hospital Stay

If a serious wound requiring 5 to 6 months of healing is suffered, a new submarine of the same type as the original will be assigned automatically (with a new crew that begins at the "Trained" level and without special skills for the other crew members). Any type of vessel available at that time may be chosen, returning to sea 1 month after being discharged from hospital.

[9.2] Reassignment Due to Prolonged Refit

If the current submarine returns and requires a maintenance and refit period of 5 months or more, a new vessel of the same type will automatically be received (and of the latest model, in the case of the Junsen and Kaidai classes). In this case, the same crew is retained with all the skills they possess, and the crew returns to sea after one month of maintenance and refit, instead of the more than 5 months otherwise required.

[9.3] Reassignment on Request

At the end of the patrol in which a commander receives the Order of the Golden Kite (4th or 5th class), he obtains an upgrade marker, which he may use to request a newer submarine model (if a more recent type is available) or to change to a different class. One or more of these upgrade markers may be kept for a later month if desired (for example, if the submarine model one wishes to obtain is not yet available). In that case, the commander retains his previous crew and puts to sea in the new vessel 1 month after having received it. The "new submarine" marker is removed from the game.

10.0 Multiplayer and Tournaments

[10.1] Two-Player Game

Both players must begin with the same type of submarine in the same month (for example, both may begin in December 1941 with Type A submarines) and continue until both have been sunk, or until a previously agreed end date. The player with the greatest tonnage sunk wins. Patrols alternate, so that one player operates his submarine while the other makes the dice rolls for the escorts' detection, their attacks, damage, and also for the aviation attacks. If optional rules are used, the player who controls the submarine at that time must decide which evasive manoeuvre to use, and the player who controls the escorts must choose a direction before the two are revealed.

[10.2] Greatest Tonnage Tournament

All players must begin on a previously agreed date, with the same type of submarine, and carry out patrols until they are destroyed or until the end of July 1945. The player with the greatest tonnage sunk wins (regardless of whether he survives or not).

[10.3] Survival Tournament

This format uses the same rules as the greatest tonnage tournament, except that the submarine is required to survive until the end of July 1945.

[10.4] Mixed Submarine Tournament

This format uses the same rules as any of the previous tournaments, except that the requirement that all players use the same type of submarine is removed; that is, players are free to choose any available class according to personal preference.

11.0 Optional Rules

[11.1] Standard Tonnage Values

If players wish, they may use a standard tonnage instead of determining ships at random by dice rolls. This should speed up play by reducing the number of rolls, at the expense of some variability and historical interest. The values are:

Small merchant: 3,500 t
Large merchant: 7,000 t
Tanker: 9,000 t

Encounters with capital ships and other naval targets must still determine their tonnage and identification (ID) through the corresponding dice rolls.

[11.2] Historical Target Selection

Players who wish to add greater historical flavour to their game, at the cost of additional control, may write the names of their targets below the tonnage on the Patrol Log Sheet. If a ship already sunk reappears as a target later on, the roll must be repeated until a previously unsunk ship is obtained. Thus, one will never sink the same ship twice in a game. Normally this is not a problem in standard games, since it rarely occurred during the testing phases in the course of a single game (although it did happen occasionally).

[11.3] Evasive Manoeuvres

At the cost of increasing the time taken by the combat sequence, players may use this optional rule to add greater tactical variety when trying to evade depth-charge attacks.

Before each dice roll on the Combat Table (assuming that detection has occurred), the player chooses a number from 1 to 6 to determine his evasion direction (left, right, or straight ahead):

1, 2 = Evasion to the left
3, 4 = Evasion to the right
5, 6 = Evasion straight ahead

A 1d6 roll is then made to determine the escort's direction:

1, 2 = Escort to the left
3, 4 = Escort to the right
5, 6 = Escort straight ahead

If the escort's direction is different from the submarine's evasion direction, the submarine receives one hit less on the Attack Table [B5] when the attack is rolled. If the escort's direction coincides with the submarine's direction, but the number chosen is not exactly the same, the submarine receives an additional hit on the Attack Table (in addition to the total hits obtained; for example, if a result of "12" is obtained, the submarine would receive 6 hits, not 5). If the escort's number is exactly the same as the evasion number chosen by the submarine, it receives 3 additional hits.

Example: the player commanding the submarine chooses the number "6", meaning he makes a straight-ahead evasion. These are the possible results of the 1d6 roll to determine the escort's direction:

1 = Wrong direction, 1 hit less.
2 = Wrong direction, 1 hit less.
3 = Wrong direction, 1 hit less.
4 = Wrong direction, 1 hit less.
5 = Correct direction, but no exact match; 1 additional hit on Table [B5].
6 = Correct direction, exact match; 3 additional hits on Table [B5].

In two-player games, both players choose their direction simultaneously and in secret, before revealing it at the same time.

Evasive manoeuvres cannot be used if the submarine has hydrophone damage.

[11.4] Variable Escort Quality

Even at the start of the war, there were significant differences in the quality of escort commanders. Some were extremely cautious (and even inept), while others were highly aggressive, determined and persistent in their attacks and tactics. In addition, there were notable differences in the quality of the equipment itself (ships, radars, sonars, etc.).

To represent this situation, players may use this rule if they wish. After making an attack against a ship (or ships) protected by escorts, but before the detection dice roll, the quality of the escort is checked by rolling 1d6:

Year	Novice	Trained	Veteran	Elite
1941-42	1	2-5	6	-
1943-44	1	2-4	5	6
1945	1	2-3	4-5	6

Novice escorts cause 1 hit less than the dice roll indicates on Table [B5].
Trained escorts use the tables normally.
Veteran escorts cause +1 hit in addition to those from the dice roll when using Table [B5].
Elite escorts apply a DRM of +1 to detection, in addition to causing +1 hit on Table [B5].

[11.5] Variable Aviation Quality

There were significant differences in the quality of the Allied air crews that pursued submarines. Some were very skilful, while others simply did not drop their depth charges or bombs accurately. In addition, different types of aircraft carried different armament. To represent these factors, players may use this optional rule. After a failed emergency dive, but before the aviation attack roll, the quality of the air crew is determined by rolling 1d6:

Year	Novice	Trained	Veteran	Elite
1941-42	1	2-5	6	-
1943-44	1	2-4	5	6
1945	1	2-3	4-5	6

Novice aviation causes 1 hit less than the dice roll indicates on Table [B5].
Trained aviation uses the tables normally.
Veteran aviation causes +1 hit in addition to those from the dice roll when using Table [B5].
Elite aviation automatically causes 2 crew casualties (instead of one automatic casualty), in addition to causing +1 hit on Table [B5].

[11.6] Historical Submarine Identification

For players who wish to assign a "historical" numeral to their submarine, a list of submarines classified by number, corresponding to the main subtypes included in the game, is given below:

Class	In-service ID
Junsen J.1M	I.5
Junsen J.2	I.6
Junsen J.3	I.7, I.8
KD.3	I.53 (later I.153); I.55 (later I.155); I.54 (later I.154); I.58 (later I.158); I.56 (later I.156); I.57 (later I.157); I.59 (later I.159); I.60; I.63
KD.4	I.61; I.62 (later I.162); I.64
KD.5	I.65 (later I.165); I.66 (later I.166); I.67
KD.6	I.68 (later I.168); I.69 (later I.169); I.70; I.71 (later I.171); I.72 (later I.172); I.73
KD.7	I.76 to I.85 (later I.176 to I.185)
Tipo A (Type A)	I.9 to I.12
Tipo A (Mod) (Type A (Modified))	I.13; I.14
Tipo B (Type B)

[11.7] Special Skills

This optional rule grants each captain (and sometimes the executive officer) an initial ability at the start of the career, although most of them grant advantages that reduce the difficulty of the game. Some of these abilities coincide with skills obtainable under rule (8.7). A 1d20 roll is made at the start of each career (or the preferred option is chosen):

1 = Lucky: begins the game with a "Maneki Neko" marker.
2 = Tracker: no roll is required to maintain contact with ships or convoys.
3 = Capital ship hunter: applies an additional DRM of -1 to hit capital ships.
4 = Teamwork: the crew begins at the "Veteran" level.
5 = Carrier hunter: applies an additional DRM of -1 to hit CV (fleet carrier) and CVE (escort carrier) targets.
6 = Aggressive: must always attack any ship contact if possible. Must always start an additional combat round against non-sunk targets that are unescorted.
7 = Bold: allows a change to a closer range if a "12" is obtained on the detection dice roll.
8 = Expert: allows bow and stern torpedoes to be fired without applying the "to hit" penalty.
9 = Vigilant: applies an additional DRM of "+1" to emergency dive rolls. (The executive officer receives the skill.)
10 = Anti-aircraft expert: anti-aircraft fire is made with an additional DRM of "-1".
11 = Leadership: promotion rolls are made after every two successful patrols, instead of after every three.
12 = Tanker hunter: applies an additional DRM of "-1" to hit targets identified as tankers.

Good luck!

11.8 Optional Name Generator

Table [H2], Names of Japanese Submarine Commanders, may help players who wish to generate a random Japanese name for the captain of their submarine.

12.0 Example of Play

Bob chooses a Type C submarine available at the start of the war. According to rule [4.5] (procedure 4), a 1d6 roll results in a 2: 12 Type 89 steam torpedoes must be stowed as reloads, and the bow and stern tubes are completed with Type 95 oxygen torpedoes. The Yokosuka marker is placed on the Control Sheet (mandatory start in December 1941), together with 5 deck gun ammunition markers and the midget submarine with its two torpedoes. He then attends the Kure Submarine School (Table [F1]). No officer gains skills, but the meditation (Gosei) grants a "Maneki Neko" amulet marker for the Control Sheet. The midget submarine's commander attends his own school (Table [F2]) and gains the skill of Superior Communications, whose marker is placed on Table [K1].

Bob now places the four initial Major Event markers on the operations map. After this, he makes a dice roll on Table [A1] to determine his patrol. Fortune finally smiles on him, since a result of "8" means that he has been assigned the attack on Pearl Harbor. On turning over the Pearl Harbor Major Event marker, the special missions shown are "Midget Submarine 1 / Reconnaissance 7 / Patrol". Since he has a midget submarine, the first special mission on the list is carried out, which is Midget Submarine 1 (this means that map M1 is used).

He then sails from Yokosuka, moving the submarine marker from "In port" to the first transit box. According to the note on Table [A3], there will be no normal encounters in transit until July 1942, unless a "12" (random event) is obtained. After obtaining an "8", the patrol proceeds. Although five track boxes are shown, the two additional transit boxes to Pearl Harbor reduce the time available, leaving only 3 effective boxes in the assigned area. As nothing happens in the second transit box, he reaches the first track box in order to carry out the special mission.

Bob now switches to map M1 for his midget submarine operation. Being a special mission, this constitutes his encounter for the first track box. He places the midget submarine in front of him, with its two torpedoes stowed and ready, places the marker in the first circular transit box, and rolls on Table [M5] for an encounter. There being none, he must now pass through the net of boats and torpedoes as shown on the map. He rolls a "5" and barely manages to cross the net, advancing to the next circular transit box. Unfortunately, here he rolls a "10", which triggers a midget submarine event (where more than one may occur). A roll of "4" on Table [M6] means that he has involuntarily surfaced, exposing the conning tower, but he then rolls a "6" and regains control under the surface. He moves to transit box no. 3, where a "7" gives another event. Here his luck runs out: a "2" means that the midget submarine is definitively lost, because Bob, unfortunately, rolls two more hull damage results in addition to the first.

Bob skips the midget submarine recovery routine, since it cannot be carried out, concluding the first track box. For the second box, he rolls a "5" on the Pearl Harbor section of Table [A3]; this would have been a re-roll had he had radar but, as he does not have it, the result is "no encounter". In his third and last track box he rolls a "7", which is a ship plus escort. A "3", according to the note below, indicates a small ship, so he consults Table [T1] and rolls a "77": the Nancy Moller, of 3,900 tons. A "2" on the day/night check (8.1.9) means it is day.

After the failure of his midget submarine, Bob decides to take revenge and fires the four bow torpedoes from medium range. Being submerged and using Type 95 torpedoes, no DRMs apply, so any result from 2 to 7 is a hit. He gets 2 hits out of the four fired, a good result, since on checking Table [B2] he sees that one is defective. The cargo ship requires two points of damage to sink, but the only Type 95 that detonates inflicts 3 points on a "2" on Table [B3], so the Nancy Moller sinks and Bob records it on his Patrol Log.

Now the escort comes looking for him but, being oxygen Type 95 torpedoes (not steam), he suffers no negative DRMs on Table [B4]. A roll of "6" means that he remains undetected and escapes. The last two transit boxes pass without incident, and Bob returns safely to Yokosuka, where he receives the Greater East Asia War Medal (8.8.6). The mission was not considered successful according to [7.3], so he gets no credit for buying skills or for advancing the crew's level. Being a Type C class ship making 2-month patrols, he was deployed in December 1941 and January 1942, with February 1942 the maintenance and refit month. His submarine will set out on its second patrol in March 1942, as it suffered no damage. The lost midget submarine will be replaced.

Designer's Notes

The creation of Sensuikan responds to requests from players who wished to experience the submarine war in the Pacific from the Japanese side. This proved complex, since the standard system of The Hunters could not be applied without major changes. In Japanese military doctrine, the submarine force was conceived as part of the "decisive battle" against the enemy fleets, and not for the interruption and harassment of lines of communication or the destruction of merchant traffic. To replicate this aspect, a system of special missions linked to the principal events of the war was designed. Instead of carrying out a patrol route with total freedom in search of ships, the Japanese player will often be obliged to maintain a picket line, transport supplies or carry out reconnaissance work. It is hoped that players will perceive the limitations that the Navy imposed on the commanders of Japanese submarines.

Another complex aspect of development lay in the eccentric designs of the Japanese Navy; "innovative" may be the more precise term. There were submarines with aviation in watertight hangars on the deck, units fitted to transport midget submarines, and kaiten suicide torpedoes. Suggestions from a close collaborator urged the inclusion of extremely detailed mini-games for these three areas. A consensus was finally reached through the development of "modules" that allow the player to focus on the direct action when midget submarines, aviation or kaiten are involved. This adds a slight degree of complexity to the game, but these modules apply only if the specific assigned submarine class has that technical capability, thus avoiding overloading the player. It is possible to complete an entire game without using any of these modules, so it was judged that this increase in complexity was acceptable, considering that its use is purely occasional. Nevertheless, the modules give the game a deep strategic dimension, something that would not have been possible without the arduous work and original concept of their designer.

Several historical factors explain the poor performance of Japanese submarines during the conflict. They had superb torpedoes and adequate fire-control systems, but suffered from a chronic lack of radar for most of the war. In addition, although Japanese submarines generally enjoyed great endurance, their diving manoeuvres were slow, they were noisy vessels, and they suffered from poor manoeuvrability underwater. Beyond these technical problems, the greatest obstacle to their effective employment was the doctrine of the Japanese high command on how they should be used. They were conceived mainly as a force multiplier for the surface fleet, and not as a force intended to paralyse or destroy enemy merchant traffic (although on occasion they did perform that task).

Add to this the formidable anti-submarine warfare (ASW) capability of the United States as the conflict advanced, and it is no surprise that the performance of these vessels was poor and that they suffered such catastrophic losses from 1943 onwards.

[The designer's signature and the names of contributors have been omitted, as credits.]

Selected Bibliography

Bagnasco, Erminio. "Submarines of World War Two." Cassell and Co, 2000. An excellent general reference work on the submarines of the principal nations, including comments on doctrine and operations. Highly recommended.
Boyd, Carl and Yoshida, Akihiko. "The Japanese Submarine Force and World War II." Naval Institute Press, 1995. [A reference work, without additional comments in the original.]
Costello, John. "The Pacific War." Atlantic Communications, Inc., 1981. Another global historical account of the whole war, but with a higher level of operational detail than other publications.
Hashimoto, Mochitsura. "Sunk: The Story of the Japanese Submarine Fleet 1941-1945." Henry Holt & Co, 1954. A faithful account from the Japanese perspective. It contains several very useful appendices.
Jordan, Roger. "The World's Merchant Fleets 1939: The Particulars and Wartime Fates of 6,000 Ships." Naval Institute Press, 1999. A work used in compiling the lists of naval and merchant targets for the game. It is not light reading, but it is an excellent reference source.
Orita, Zenji. "I-Boat Captain." Major Books, 1976. A solid first-person account written by the commander of a Japanese submarine. It presents certain subjective biases proper to the author, an aspect that is understandable given the nature of the work.
Rohwer, Jürgen. "Axis Submarine Successes of World War Two." Greenhill Books, 1999. Although most of the records correspond to the German U-boats, the sections dedicated to Japanese submarines have proved of incalculable value for the development of the game.
Spector, Ronald. "Eagle Against the Sun." The Free Press, 1984. A large-scale general historical account of the entire Pacific War.
Stille, Mark. "Imperial Japanese Navy Submarines 1941-45." Osprey Publishing, 2007. A classic Osprey publication with excellent illustrations and technical details of the submarine arm.