25. SUBMARINE WARFARE
25.1 SUBMARINES
25.2 ASW
25.3 USE OF NAVAL UNITS IN SW BOXES
25.4 SUBMARINES AND ASW
25.5 SUBMARINE BASES
25.6 SUBMARINE WARFARE MODIFIERS
25.7 THE ATLANTIC
25.8 THE INDIAN OCEAN
25.9 THE PACIFIC

25.1 SUBMARINES:
25.11 TACTICAL AND STRATEGIC USE OF SUBMARINES: Submarines may operate on the board, basing, moving, intercepting and NRing like other naval units except where noted (22.9), or may operate in the SW boxes against enemy transports.
25.12 TRANSFER OF SUBMARINES TO AND FROM THE SW BOX: A player may move all, some or none of his submarines to or from an SW box during the redeployment phase. Submarines may not enter or leave an SW box during the movement phase.
25.121 Submarines which attacked enemy naval units on the board during their player turn and are then redeployed into an SW box during the redeployment phase of that player turn remain inverted until the end of the following enemy player turn, and are thus available for SW only during the owning player's next player turn.
25.122 Submarines which are redeployed onto the board from an SW box during the redeployment phase of their player turn remain inverted until the end of the following enemy player turn, whether or not they engaged in SW during their player turn.
25.13 USE OF SUBMARINES IN THE SW BOXES: In order to engage in submarine SW combat in an SW box, submarines must begin their player turn in that SW box. The use of submarines for SW combat is restricted as follows:
A. GERMANY:
B. ITALY:
C. JAPAN:

If Japan attacks the U.S. in Winter 1941, Japanese submarines may only enter the Pacific and Indian Ocean SW boxes in the redeployment phase of the Winter 1941 Japanese player turn, and the first Japanese submarine attacks against Western Allied transports would occur during the combat phase of the Spring 1942 Japanese player turn.

D. BRITAIN:
E. U.S.:
25.14 SUBMARINES MAY DECLINE SW COMBAT: Submarines in an SW box may decline to engage in SW combat. When this occurs, the defender’s transports are unaffected by the enemy submarines in that SW box.
25.15 GERMAN SUBMARINES IN THE MEDITERRANEAN: Germany may NR one submarine factor each turn past a Western Allied-controlled Gibraltar:
A. WESTERN FRONT PORT: Between a western front port and a Mediterranean port, subject to the range restrictions set out in 21.3612; or
B. ATLANTIC SW BOX: Between the Atlantic SW box and a Mediterranean port, without regard to range restrictions.
25.151 More than one German submarine factor may be transferred in a single turn if the Axis control Gibraltar. Italian submarines may not pass by a Western Allied-controlled Gibraltar.
25.16 WESTERN ALLIED SUBMARINES IN THE MEDITERRANEAN: Similarly, the Western Allies may transfer one submarine factor each turn between the western front and a Mediterranean port if the Axis control Gibraltar.

25.2 ASW:
25.21 ASW OPERATE FROM SW BOXES: ASW may only operate from an SW box. Newly constructed ASW may remain in port, change bases or deploy into an SW box, but may not operate from ports or mapboard boxes. ASW intercepted and attacked on the mapboard are treated as destroyers.
25.22 USE OF ASW IN SW BOXES:
A. The Western Allied ASW listed as a British starting unit begins the game in the Atlantic SW box.
B. The Western Allied ASW listed as a British allowable build may only be constructed in a British or Canadian shipyard and may deploy to any SW box.
C. The Western Allied ASW listed as an American starting unit and the Western Allied ASW listed as an American allowable build, which may only be constructed in an American shipyard, are both subject to the restrictions set out in 25.32 until the U.S. is at war in both theaters.
D. Western Allied ASW generated by production (42.23B) may deploy to any SW box if constructed in British or Canadian shipyards; if constructed in an American shipyard, such units are subject to the restrictions set out in 25.32 until the U.S. is at war in both theaters.
E. Japanese ASW may not deploy to the Pacific SW box prior to the outbreak of war between Japan and the U.S.

25.3 USE OF NAVAL UNITS IN SW BOXES:
25.31 DEPLOYMENT OF NAVAL UNITS TO AN SW BOX: The U.S., Britain and Japan (Pacific only) may deploy both inverted and uninverted naval units, ASW and transports, regardless of supply status and oil effects, to the SW boxes during the movement (EXCEPTION: Submarines - 25.12) or redeployment phases; Germany may deploy submarines to the Atlantic and Indian Ocean SW boxes during the redeployment phase. Western Allied naval units may be freely transferred between all three SW boxes during the redeployment phase and are subject to the normal effects of redeployment (24.52, 25.121, 28.82), but their deployment to the SW boxes is otherwise subject to the following restrictions:
A. ATLANTIC: British and American naval units deployed to the Atlantic SW box must be based in a western front port, the Atlantic U.S. box or the South Africa box. Axis naval units may not deploy to the Atlantic SW box (EXCEPTION: German submarines deployed to the Atlantic SW box must be based in a Western front or Mediterranean port).
B. PACIFIC: British and American naval units deployed to the Pacific SW box must be based in Pearl Harbor, Tahiti or the Pacific U.S. or Australia boxes. Japanese naval units deployed to the Pacific SW box must be based in Japan or Truk.
C. INDIAN OCEAN: British and American naval units deployed to the Indian Ocean SW box must be based in Suez, Basra, Abadan, Colombo, Madras or the South Africa, Australia or India boxes. German submarines deployed to the Indian Ocean SW box must be based in a Mediterranean port. Japanese submarines deployed to the Indian Ocean SW box must be based in Japan or Singapore.
D. Only British and American naval units may enter SW boxes. Other Western Allied naval units may not enter the SW boxes.
25.32 TENSION RESTRICTIONS:
A. USAT:
B. USJT: If the USJT level is 40 or greater, the U.S. may deploy one ASW factor (25.22C, D) per turn to the Pacific SW box.
25.33 INTERCEPTION: Naval units may not be intercepted when moving or redeploying between mapboard boxes and SW boxes. Movement and NRs to and from SW boxes may be intercepted in mapboard hexes as follows:
A. ATLANTIC: British and American naval units may be intercepted as they move between western front ports and the western edge of the mapboard.
B. PACIFIC: British and American naval units may be intercepted as they move between Pearl Harbor or Tahiti and the eastern edge of the mapboard. Japanese naval units may be intercepted in Truk or a port in Japan.
C. INDIAN OCEAN: Western Allied naval units may only be intercepted by air as they move or redeploy from Suez, Basra or Abadan to the southern edge of the European mapboard. British and American naval units may be intercepted by Japanese air and naval units as they move between Colombo or Madras and the western edge of the Pacific mapboard.
25.34 REDEPLOYMENT OF INVERTED NAVAL UNITS: Inverted naval units may be redeployed to an SW box, but they remain inverted and may not perform any functions during the next opposing player turn.
25.35 FUNCTIONS: While in an SW box, uninverted naval units are restricted to the following functions:
A. Conducting or protecting naval activities which employ transports in that SW box (oil shipments, sea supply, naval missions or BRP grants - 20.64A-D) or protecting sea supply in the Pacific theater (30.361D-F).
B. Shore bombardment or fast carrier missions associated with seaborne invasions from the U.S., Australia or India boxes (Western Allied naval units only) (21.523, 21.553), provided that the seaborne invasion originates solely from the mapboard box (5.931D).
C. The protection of naval units changing base or redeploying to or from a mapboard box, through that SW box (21.224, 28.72B, 28.73D).
D. Anti-submarine warfare (CVEs only) (25.362).
E. Raider interception (Western Allied naval units only) (21.5342G).
25.36 MULTIPLE FUNCTIONS: Naval units in an SW box which participate in or protect naval activities passing through their SW box are not inverted unless damaged in combat or withdrawn from the SW box (25.37), and may therefore be used more than once to protect different naval activities which pass through their SW box at different times in the same player turn (such as sea supply during initial supply determination, sea transport, seaborne invasions, BRP grants during post-combat supply determination and NRs). If more than one naval activity of the same type is being carried out at the same time, such as sea supply lines being traced to different ports during the same phase, the moving player must indicate which naval units are protecting which naval activity before enemy air or naval attacks on that naval activity are announced or attempted.

A prudent Western Allied player will place a TF in the Atlantic SW box as long as there is an Axis naval threat against the Atlantic transports. This speeds play, because most Axis players won't even try to intercept protected Western Allied transport activities, and even a weak TF will buy time for additional Western Allied naval units to arrive on the scene if the Axis do intercept. The TF need not be as strong as the threatening Axis naval forces, although it could and often should be, and only the Western Allied player will know for sure. Until the German navy is destroyed or hemmed in by Western Allied land-based air, the Western Allied player should also keep additional naval forces available to counter-intercept.
If the German navy is super-sized or the Axis have captured Gibraltar and the Italians are also coming to the party, the Western Allied player will have to deal with it.

25.361 DESTROYERS: Japanese, British and American destroyers in an SW box may absorb losses from enemy onboard submarine attacks (22.9432).
25.362 CVEs: CVEs are used for anti-submarine duties while in an SW box. The number of uninverted CVEs modifies the SW combat dice rolls for submarines and ASW. Fast carriers have no effect on SW.
25.363 RAIDERS: Uninverted naval units in an SW box are eligible to engage enemy raiders.
25.37 WITHDRAWAL OF UNITS FROM SW BOXES: Naval units and SW units (submarines and ASW) may be withdrawn from SW boxes during either the movement (EXCEPTION: Submarines - 25.12) or redeployment phases, whether or not they were employed during the owning player’s turn or the preceding opponent’s player turn. Naval units and SW units must withdraw to a location from which they were eligible to enter the SW box in question (25.31). Japanese naval units which withdraw from the Pacific SW box to Japan or Truk during the redeployment phase may protect naval redeployments to Japan or Truk, as the case may be. Western Allied transports may be redeployed between SW boxes, but must always end the turn in a SW box; Japanese transports must always end the turn in the Pacific SW box (20.622).
25.371 WITHDRAWAL OF DAMAGED NAVAL UNITS: Naval units which are damaged during naval combat while in an SW box must withdraw to an adjacent port or mapboard box (25.31) at the end of that naval combat.
25.372 INVERSION OF WITHDRAWING NAVAL UNITS:
A. Naval units which withdraw from an SW box in the movement phase are inverted for the remainder of their player turn.
B. Naval units which withdraw from an SW box in the redeployment phase are inverted for the remainder of their player turn and for the next opposing player turn.
25.38 TRANSFERS OF UNITS BETWEEN SW BOXES: Naval units and SW units may be transferred between SW boxes during the redeployment phase, whether or not they were employed during the owning player's turn or the preceding opponent's player turn, are not inverted after transfer, and may be used in the next player turn (24.52).

25.4 SUBMARINES AND ASW:
25.41 SUBMARINES: The attacker's submarine level is determined by the number of submarine factors in the SW box in question.
25.42 ASW: The defender's ASW level is determined by the number of ASW factors in the SW box in question.

25.5 SUBMARINE BASES:
25.51 PORTS: Submarine warfare depends on the availability of bases from which the submarines in the SW box in question are considered to be operating:
A. GERMANY: German submarines may conduct SW in the Atlantic SW box only from an Axis-controlled operational port on the western front, and may conduct SW in the Indian Ocean SW box only from an Axis-controlled operational Suez.
B. JAPAN: Japanese submarines may conduct SW from any operational port controlled by Japan.
C. U.S.: American submarines may conduct SW from the Australia box or any Pacific front operational port controlled by the Western Allies.

25.6 SUBMARINE WARFARE MODIFIERS:
25.61 SUBMARINE AND ASW SW COMBAT DICE ROLLS: The following modifiers apply to submarine and ASW SW combat dice rolls (positive modifiers favor submarines):

SW Combat Modifiers Table

Submarine warfare

General:

+/-#

Naval Nationality DRM (22.552A)

+/-#

air range research levels

+#

attacker torpedo research level

-#

defender ASW research level

Atlantic:

-1

for every 6 CVEs in the Atlantic SW box (round down): 0-5: 0; 6-11: -1; 12-17: -2; 18-23: -3; 24+: -4

+2

Axis control Brest, Lorient, St. Nazaire or La Rochelle

+1

Axis control La Coruna, Vigo, Lisbon or Cadiz

+1

Axis control Gibraltar

+1

Germany and the U.S. are at war

+#

Germany and the U.S. are at war: first turn: +2; second turn: +1 (25.66)

+1

a diplomatic result for Ireland of "7" or more

+/-1

Ultra codebreaking advantage

Indian Ocean:

-1

for every 3 CVEs in the Indian Ocean SW box (round down): 0-2: 0; 3-5: -1; 6-8: -2; 9-11: -3; 12+: -4

+1

Japan controls Colombo (Japanese submarines only)

+/-1

Ultra codebreaking advantage (German submarines only)

+/-1

Magic codebreaking advantage (Japanese submarines only)

Pacific:

-1

for every 3 CVEs in the Pacific SW box (round down): 0-2: 0; 3-5: -1; 6-8: -2; 9-11: -3; 12+: -4

+1

Japan controls Townsville, Noumea, Suva or any port in the Hawaiian Islands (Japanese submarines only)

+2

Allies control Manila (American submarines only)

+/-1

Magic codebreaking advantage


25.62 GENERAL MODIFIERS:
25.621 NAVAL NATIONALITY DRMs: The attacker's and defender's Naval Nationality DRMs are compared.
25.622 TORPEDO AND ASW RESEARCH RESULTS: The attacker's torpedo and the defender's ASW research results are compared. The attacker's ASW and the defender's torpedo research results are disregarded. An "8+" ASW research result is implemented gradually, over two turns (41.84).
25.623 AIR RANGE: The attacker's and defender's air range research results are compared. ASW modifiers resulting from air range research apply only when resolving SW combat. Air range modifiers do not affect the resolution of submarine attacks on the board.
25.63 INITIAL MODIFIERS:
25.631 NAVAL NATIONALITY DRMs: Germany and Japan begin the game with a +1 advantage in Naval Nationality DRM in submarine warfare.
25.632 JAPANESE TORPEDOES: Japan begins the game with one torpedo research result to reflect the Japanese Long Lance torpedoes. Because the Japanese torpedo result was achieved prior to the outbreak of war, Japan does not incur a -1 modifier from its pre-war torpedo research result.
25.64 CVEs: The number of CVEs in an SW box (25.362) modifies the SW combat dice rolls for both sides as follows:
A. ATLANTIC:
B. PACIFIC AND INDIAN OCEANS:
25.641 FAST CARRIERS NOT COUNTED: Fast carriers may not be used for anti-submarine warfare.
25.65 DISTANCE FROM SUBMARINE BASES: The control of specified fully supplied ports modifies submarine warfare, as set out in 25.723 (Atlantic Ocean), 25.811 (Indian Ocean) and 25.92 (Pacific Ocean).
25.66 EFFECTS OF WAR BETWEEN GERMANY AND THE U.S.: The outbreak of war between Germany and the U.S. affects submarine warfare as follows:
A. Each turn Germany and the U.S. are at war, a pro-German +1 modifier applies to German and Western Allied submarine/ASW SW combat dice rolls.
B. In addition, regardless of which country declares war on the other:
25.67 CODEBREAKING:
25.671 NUMBER OF CARDS PLAYED COMPARED: Each turn the number of Ultra/Magic submarine warfare and ASW cards played are compared for each of the possible submarine warfare campaigns, as follows:
A. ATLANTIC AND INDIAN OCEAN (German submarines): European Axis Ultra submarine warfare cards vs. British Ultra ASW cards.
B. PACIFIC AND INDIAN OCEAN (Japanese submarines): Japanese Magic submarine warfare cards vs. American Magic ASW cards.
C. PACIFIC (American submarines): American Magic submarine warfare cards vs. Japanese Magic ASW cards.
25.672 EFFECTS: The play of a submarine warfare card, unless offset by the play of an opposing ASW card, generates a favorable +1 modifier for submarine warfare in the affected SW boxes for that turn. Similarly, the play of an ASW card when there is no opposing submarine warfare card to offset it generates a favorable -1 modifier against submarine warfare in the affected SW boxes for that turn.
25.673 MAXIMUM +/-1 MODIFIER: The play of two or more submarine warfare or ASW cards more than the opponent still only generates a favorable +/-1 modifier for strategic submarine warfare in the affected SW boxes for that turn.

25.7 THE ATLANTIC:
25.71 GENERAL: German submarines operating in the Atlantic SW box may conduct submarine warfare against the Western Allied Atlantic transports in the Atlantic SW box (24.6, 25.4, 25.6).
25.72 SUBMARINE EFFECTIVENESS:
25.721 German submarines in the Atlantic SW box may not be used for SW if the Axis do not control an operational port on the western front.
25.722 The number of Western Allied CVEs in the Atlantic SW box modifies the SW combat dice rolls for both sides (25.64).
25.723 Germany receives the following modifiers for submarine warfare in the Atlantic: +2 if the Axis control Brest, Lorient, St. Nazaire or La Rochelle; +1 if the Axis control La Coruna, Vigo, Lisbon or Cadiz; +1 if the Axis control Gibraltar. To gain each favorable modifier at least one of the listed ports must be controlled and fully supplied by the Axis. Each "+" modifier generates a corresponding "-" modifier and vice versa.
25.724 Germany obtains a favorable modifier for submarine warfare when it goes to war with the U.S., because the American east coast shipping is not yet organized into convoys (25.66).
25.725 Germany receives a +1 modifier in the Atlantic if a "7" or greater diplomatic result for Ireland is in effect.
25.726 Either side may obtain a favorable modifier for codebreaking (25.67).
25.73 ADVANCED SUBMARINES: German advanced submarines make a separate SW combat dice roll against Western Allied transports after the resolution of raider combat and conventional submarine warfare:
A. Each advanced submarine factor counts as three factors on the SW Combat Table.
B. No modifiers are applied to the advanced submarine SW combat dice roll.
C. No SW combat dice roll is made by the Western Allies.
D. One Western Allied transport is eliminated for each advanced submarine in the SW box.

25.8 THE INDIAN OCEAN:
25.81 JAPANESE SUBMARINES: Japanese submarines may not enter the Indian Ocean SW box until the turn in which war breaks out between Japan and Britain.
25.811 JAPANESE SUBMARINE EFFECTIVENESS: Japan receives a +1 modifier for submarine warfare in the Indian Ocean if it controls and fully supplies Colombo.
25.83 JAPANESE AND GERMAN SUBMARINES IN THE INDIAN OCEAN: If both German and Japanese submarines are operating in the Indian Ocean SW box, the Western Allies split their ASW forces as desired and two separate submarine warfare SW combats are resolved simultaneously.

25.9 THE PACIFIC:
25.91 SUBMARINE EMPLOYMENT: Japanese and American submarines may not enter the Pacific SW box until the turn in which war breaks out between Japan and the U.S. or the USJT level reaches 40 or more. Both sides may use submarines based on the mapboard to attack enemy naval units. Submarines may not pass by an enemy-controlled Singapore (hex EE11).
25.92 SUBMARINE EFFECTIVENESS:
A. JAPAN: Japan receives a +1 modifier for submarine warfare in the Pacific if it controls and fully supplies one or more of Townsville, Noumea, Suva or any port in the Hawaiian Islands.
B. U.S.: The U.S. receives a +2 modifier for submarine warfare in the Pacific if it controls Manila.