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Island War

Standard Rules
for the games
Bloody Ridge, Saipan, Leyte, Okinawa

Copyright © 2009 Decision Games, California, USA and Decision Games, Fortrose, UK.


[1.0] Introduction

The Island War game system is a simulation of World War II ground combat in the Pacific Theater. Each game in the system represents a clash between American and Japanese forces on one of the many Pacific islands. The playing pieces represent the actual units which participated in the battles, and the map represents the actual terrain over which those units fought. Two sets of rules provided. These, the common rukes, contain Standard Rules, which are common to all the games in the Island War system. The Exclusive Rules for each game in the system contain the Initial Deployment, Reinforcement Rules, Scenario Specific Details and the Victory Conditions.

The game has been designed to insure maximum playability and maximum reality (in that order). In order to achieve these goals, the physical components, as well as the game rules, have been designed to make the game easier to understand and play. The components include a small, compact playing map, never more than a hundred playing pieces, and standardized rules.

The standardization makes it easier for the gamer to go from one game to another within the series. It also enables the games' designers to concentrate on the realism aspect of the games. (The standardization generally takes care of any playability problems.)

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[2.0] Game Equipment

[2.1] The Game Map

Each of the maps sheets portrays the battle area. A hexagonal grid is superimposed over the terrain features on the map sheet in order to regularize movement and the positioning of the playing pieces.

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[2.2] Charts and Tables

Various visual aids are provided for the Players in order to simplify and illustrate certain game functions. These are the Combat Results Table, the Terrain Key, and the Turn Record/Reinforcement Track.

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[2.3] The Playing Pleces

The playing pieces represent the actual military units that took part in the historical battle. The numbers and symbols on the pieces represent the strength, movement capability, and type of unit represented by the piece. These playing pieces will hereafter be referred to as 'units'.

[2.31] How to Read the Units

Unit Designations:

The regiment to which the battalion belongs is shown to the right of the slash. In Leyte, detached battalions bear only the identity of their regiment. Unit Sizes:

I = Company, II = Battalion, III = Regiment.

[2.32] Definition of Terms

Attack Strength is the relative strength of a non-artillery unit with regard to attacking other units, expressed in terms of Attack Strength Points.

Defense Strength is the relative strength of a unit with regard to defending against the attacks of Enemy units, and is expressed in terms of Defense Strength Points.

Barrage Strength is the relative strength of an Artillery unit when attacking Enemy units, and is expressed in terms of Barrage Strength Points. Final Protective Fire (FPF) Strength is the relative ability of an Artillery unit to add to the Defense Strength of Friendly units, and is expressed in terms of FPF Strength Points.

Movement Allowance is the maximum number of clear terrain hexes through which a unit may be moved in a single Movement Phase; each such hex requires one Movement Point of the Movement Allowance. More than one Movement Point may be expended for some hexes.

Range Allowance is the maximum number of hexes from the hex of an Artillery unit using its FPF or Barrage Strength (exclusive), to the defending Unit's hex (inclusive).

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[2.4] Game Scale

Each hexagon on the map sheet represents from 500 to 2000 yards of real terrain from side to side. Each Game-Turn is equivalent to one or two days of real time.

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[3.0] Setting Up the Game

The differently colored units represent forces of opposing sides. Unit values are listed as follows: Attack Strength / Defense Strength / Movement Allowance. For Artillery units: Barrage Strength / Final Protective Fire Strength / Range Allowance / Defense Strength / Movement Allowance. Units may be assigned specific set-up hexes or Players may be instructed to choose, the set-up hexes for their units, in which case one Player or the other will be instructed to deploy first. Each reinforcement unit should be placed in a space on the Turn Record/Reinforcement Track which depicts a unit of its type. If there is no quantity indication (x1, x2, etc.), only one unit of the type shown is received.

The date of the Game Turn is the opening date of the historical period represented.

The Scenario Special Rules indicate which Player is the First Player. The Scenario Victory Conditions tell how the game is won. Play proceeds according to the Sequence of Play for the number of Game-Turns specified in the Scenario.

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[4.0] Sequence of Play

This game is played in successive Game-Turns, composed of alternate Player-Turns. During each Game-Turn the Players maneuver their units and resolve combat in sequence, according to the following outline and within the limits provided by the rules which follow. At the conclusion of the last Game-Turn, the Victory Conditions are consulted and a winner is determined.

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[4.1] Sequence Outline

The Game-Turn

The Game-Turn is divided into a First Player-Turn and a Second Player-Turn. The Player whose Player-Turn is currently in progress is termed the Phasing Player. The activity which may take place during each Phase is outlined below.

1. First Player-Turn

A. Movement Phase: The Phasing Player may move all, some or none of his units as he desires within the limits and restrictions of the rules of Movement, Zones of Control, Terrain Effects and Exclusive Rules of the game. The Phasing Player may bring Reinforcements onto the map as allowed by his Reinforcement Schedule and the Reinforcement Rules. The non-Phasing Player may not move his units.

B. Combat Phase: The Phasing Player uses his units to attack the non-Phasing Player's units. The Phasing Player may execute his attacks in any order he desires. Each attack follows the following sub-sequence where appropriate.

a. The Phasing Player states the number and strength of his attacking ground units.

b. The Phasing Player allocates Barrage Strength Points (if he wishes) from Artillery units and Ground Support Points.

c. The system AI allocates allocates Final Protective Fire Strength on behalf of the non-Phasing Player from non-adjacent Artillery units and Ground Support Points.

d. The Combat Differential (total attacking strength minus total defending strength) is calculated, the terrain-type occupied by the defending unit is found and the combat differential column from that line is consulted. A six sided virtual die is rolled by the system referenced to the 'Combat Results Table' and the indicated result is immediately applied.

During the Combat Phase, neither Player may move his units, except when called for as a result of combat.

2. Second Player-Turn

The Second Player now becomes the Phasing Player and executes Movement and Combat in the sequence described above.

3. Game-Turn Record interphase

The Turn is advanced signaling the start of a new Game-Turn.

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[5.0] Movement

General Rule:

During the Movement Phase, the Phasing Player may move as many or as few of his units as he desires. The units may be moved in any direction or combination of directions.


Units are moved one at a time, tracing a path of contiguous hexes through the hex grid. As each Unit enters a hex, that unit pays one or more Movement Points from its Movement Allowance.


[5.1] Movement Restrictions and Prohibitions


Movement may never take place out of sequence. A Player's units may be moved during his own Movement Phase. During the Combat Phase, a unit which is either attacking or defending may be called upon to advance or retreat after Combat is resolved. During the Enemy Player's Movement Phase, and during both Players' Combat Phases, except when advancing or retreating as a result of Combat, Friendly units must not be moved.


A Friendly unit may never enter a hex containing an Enemy unit.


A unit may never expend more Movement Points than its total Movement Allowance in any one Movement Phase. A unit may expend all, some or none of its Movement Points in any one Game-Turn, but unused Movement Points may not be accumulated until another Movement Phase or transferred to another unit.


An American unit may never exit a Japanese controlled hex during any Movement Phase. A Japanese controlled hex may be exited only during a retreat or advance as a result of Combat.


Japanese armored or Artillery units may never exit an American controlled hex during any Movement Phase. These units may exit from an American controlled hex only during a retreat or advance as a result of Combat. Japanese infantry and engineer units may exit American controlled hexes (see 6.14).


Once a unit has been moved and second unit has been moved the unitial unit may not be moved any further during the Player Turn nor may it change its move without the consent of the opposing Player. (In some circumstances the 'Take Back' option will be available on the system menu bar).


There are no supply rules (unless otherwise noted in a specific game's Exclusive Rules). Units are considered to be 'in supply' at all times. Isolation has no effect on Movement or Combat.

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[5.2] Effects of Terrain


A unit must expend one Movement Point to enter a clear terrain hex. To enter other types of hexes, a unit must expend more than one Movement Point. When the Terrain Key calls for a Movement Point expenditure to cross a terrain hexside, this cost is in addition to the terrain cost for entering the hex. Movement Point costs are summarized on the Terrain Key on the map. Movement Point costs are cumulative.


A unit which moves from one road hex directly into an adjacent road hex through a road hexside expends only half a Movement Point, regardless of other terrain in the hex.


A unit which moves from one trail hex directly into an adjacent trail through a trail hexside expends one Movement Point, regardless of other terrain in the hex.


A unit may not enter a hex if it does not have sufficient Movement Points remaining to pay the Movement Point cost to enter the hex itself and the hexside being crossed.


Armored units may enter only clear and Town hexes; they may enter any other hex only via a road or trail hexside.

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[5.3] Effects of Other Friendly Units


A Friendly unit may move through hexes occupied by other Friendly units (at no extra Movement Point cost), but may not end the Movement Phase stacked in the same hex with another Friendly unit. Stacking is prohibited.


There is no limit to the number of Friendly units that can pass through a single hex in one Game-Turn.


Friendly controlled hexes never interfere with Friendly movement.

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[6.0] Zones of Control

General Rule:

The six hexagons immediately surrounding a hex constitute the Zone of Control (ZOC) of any unit in that hex. Hexes upon which a unit exerts a Zone of Control are called Controlled Hexes and inhibit the movement of Enemy units. All units must cease movement when they enter an Enemy controlled hex.


[6.1] Effects on Movement


All units exert a Zone of Control at all times, regardless of the Phase or the Player-Turn, during the entire Game-Turn. The presence of Zones of Control is never affected by other units, Enemy or Friendly.


Units do not pay any additional Movement Points to enter an Enemy-controlled hex.


There are only two ways for a unit (except Japanese infantry and engineer units) to exit an Enemy controlled hex: either by retreat or advance as a result of Combat, or by removal of the Enemy unit exerting the Zone of Control as a result of Combat.


Japanese infantry and engineer units which begin the Movement Phase in an American controlled hex may move to any adjacent hex. They may move one, and only one hex; they may even move directly from one American controlled hex to another American controlled hex. Note that this rule does not allow Japanese units to retreat into or through American controlled hexes as a result of Combat.


Zones of Control extend into all types of terrain hexes and across all types of terrain hexsides.

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[6.2] Multiple Zones


If there are both Enemy and Friendly Zones of Control cast over a given hex, they have no affect on each other; both Zones co-exist and the hex is mutually controlled by both Players.


There is no additional effect when more than one unit casts its Zone of Control onto a given hex.


Obviously, if a given unit is in an Enemy controlled hex, the Enemy unit is also in its controlled hex. The two units are equally and mutually affected.

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[7.0] Combat

General Rule:

Combat between adjacent opposing units is mandatory. Artillery units (8.0) are the only units which may attack units to which they are not adjacent. See also Ground Support Rules (9.0).

The Phasing Player is termed the Attacker; the other Player the Defender, regardless of the overall strategic situation.


Total the Attack Strength, Barrage Strength and Ground Support Strength of all attacking units involved in a specific attack; total the Defense Strength and the Final Protective Fire of all units which are the object of a specific attack. Subtract the total Strength of the defending units. The result is the Combat Differential expressed in Points. It may be either a positive or a negative number.

Consult the Combat Results Table, find the terrain-type which the defending unit occupies, directly across that line find the appropriate combat differential column, roll the die under that column heading, and then apply any Combat Results immediately, before resolving any additional attacks that are being made in the same Combat Phase. Example: If thirteen Strength Points were attacking a unit with four Strength Points in a Jungle hex, the Combat Differential would be a +9. The attack would be resolved at +8-9 on the line corresponding to Jungle terrain. [A die roll of one would result in a D-3.]

Having determined the proper column on the Combat Results Table (7.61), the attacker rolls the die. The result indicates a line which is cross-indexed with the proper column. The intersection of line and column yields a Combat Result. This should be immediately applied to the involved units, before going on to resolve any other combat. Separate combats may be resolved in any order that the attacker wishes, so long as all combats are resolved during that Combat Phase.


[7.1] Which Units Attack


Each non-Phasing unit that has a Phasing unit adjacent to it must be attacked by some Phasing unit during that Combat Phase. The Phasing Player may resolve these attacks in any fashion desired, so long as all adjacent units are attacked within the requirements of rule 7.2.


All of the Phasing Player's units which end the Movement Phase in an Enemy controlled hex must attack some Enemy unit during the ensuing Combat Phase. The Phasing Player may choose which units will attack each defending unit, as long as all adjacent Friendly units participate in an attack.


A defending unit may be attacked by as many as six adjacent units, with possible additional Artillery Barrage Strength (see 8.0) and Ground Support (see 9.0).


No unit may attack more than once per Combat Phase, and no Enemy unit may be attacked more than once per Combat Phase.


Non-Artillery units may attack only if in a hex adjacent to the defending unit.

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[7.2] Multiple Unit and Multi-Hex Combat


If a Phasing Player's unit is in a Zone of Control of more than one Enemy unit, it must attack all those adjacent Enemy units which are not engaged by some other attacking unit.


Units in two or more different hexes may combine their Combat Strengths and attack a single hex, if all the attacking units are adjacent to (or are within range of) the Enemy occupied hex.


Attacks may involve any number of attacking or defending units. For the attacks to be resolved as a single combat, however, all the attacking units must be adjacent to all the defending units, with the addition of Barraging Artillery units, which need not be adjacent.

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[7.3] Combat Strength Unity

A given unit's Attack and Defense Strengths are always unitary. That is, a unit's Strength may not be divided among different combats, either for attack or defense.

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[7.4] Effects of Terrain


Defending units, only, benefit from the terrain in the hex they occupy and/or that hex's perimeter hexsides. Terrain in hexes occupied by attacking units has no effect on combat.


Defending units do not benefit from River hexsides unless all units attacking that defending unit are attacking across River hexsides.


The effect of terrain (on combat) has been integrated into the Combat Results Table. Simply find the terrain which the defending unit benefits from, trace over to the proper Combat Differential column, and roll the die under that column heading.


Terrain benefits for combat are not cumulative. A defending unit always benefits only from the most advantageous terrain. Example: A unit in rough terrain behind a River hexside would benefit from the rough terrain only.


When two or more defending units are being attacked in a single combat and are on two different types of terrain, each having a different effect on the Combat Differential, then all defending units benefit from the terrain most favorable to the defender.

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[7.5] Diversionary Attacks


In making a series of attacks, a Player may allocate his attacking units so that some attacks are made at 'poor' Differentials, so that adjacent attacks may be made at more advantageous Differentials (by allotting most of the attacking force to the major objectives). These attacks are known as diversionary or holding attacks.


The Phasing Player may never voluntarily reduce the Differential of any given attack. That is, he may never voluntarily shift to the left of his Combat Differential column.

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[7.6] Combat Resolution

[7.61] Combat Results Table

(See separate sheet.)

[7.62] Explanation of Results

D1, 2, 3 = Defender Retreats the indicated number of hexes (1,2,3). The computer AI retreats all players units. These must retreat his units in accordance with the Retreat Rules (see 7.7). Units may not retreat across prohibited hexsides (see Terrain Key).

A1, 2, 3  = Attacker Retreats as above.

Ae = Attacker Eliminated. Defender may advance into the hex (The computer AI decides on this and will usually only advance to take an objective or to change the current game result).

De = Defender Eliminated. Attacker may advance into the hex.

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[7.7] How To Retreat

When the Combat Result requires a Player's unit(s) be retreated, the Owning Player must immediately move those units the indicated number of hexes away from their combat position. This movement is not normal movement and is subject to the following restrictions. If the unit is unable to retreat within these restrictions, it is eliminated instead.


In retreating, a unit may initially leave an Enemy controlled hex; thereafter it may not enter an Enemy controlled hex. Friendly units do not negate Enemy Zones of Control for purposes of retreat.


A retreating unit may not cross a prohibited hexside (see Terrain Key).


Where possible, a retreating unit must retreat into and through vacant hexes. If no other route is available, the retreating unit may move through Friendly occupied hexes, displacing every Friendly unit whose hex it moves into or through (see 7.8).


In all cases, the retreating unit must terminate its retreat the Combat Result-indicated number of hexes away from its former combat position. If it cannot, and can retreat only a portion of the number of obligated hexes, it is eliminated in the last hex to which it is able to retreat. The retreat path (see 7.91) terminates in the hex a unit is eliminated in.

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[7.8] Displacement


If Friendly units occupy hexes in the only possible retreat route available to a retreating unit, those Friendly units are displaced (moved out of their hexes) by the retreating unit. The displaced unit is moved one hex (by the Owning Player) as if it were itself retreating. Then the retreating unit enters the vacated hex and, if necessary, continues its retreat. The retreating unit may displace as many units as necessary to retreat the indicated number of hexes.


If the displacement would cause any of the displaced units to be eliminated, the retreating unit is eliminated instead. Displaced units can themselves displace other Friendly units in a sort of chain reaction of displacement, if that is the only permitted path of displacement open to them. A unit may be displaced more than once per Combat Phase, if that is the only alternative. Displaced Artillery units which have not yet engaged in combat, may not fire during that Combat Phase. Units may not displace other Friendly units if they have other paths of retreat open to them.


If a retreating unit displaces a unit in a hex which the Phasing Player had intended to Barrage Attack, the attack against that hex may not take place. Of course, the displaced unit may be Barrage Attacked in its new hex.

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[7.9] Advance After Combat


Whenever an Enemy unit is forced to retreat (or is eliminated) as a result of combat, it will leave a path of vacant hexes behind it called the Path of Retreat (this includes hexes vacated pursuant to 7.74). Any or all Friendly victorious units which participated in the combat and were adjacent to the retreated unit are allowed to advance along the Enemy Path of Retreat.


The advancing victorious units may cease advancing at any hex along the Path of Retreat.


Advancing victorious units may ignore Enemy Zones of Control.


Only victorious units which were adjacent to the retreating unit during the combat and participated in that combat may advance. Non-adjacent Artillery units may not advance after combat.


An advancing unit may not stray from the Path of Retreat.


The option to advance must be exercised immediately before any other combat resolution. Units are never forced to advance after combat. After advancing, units may neither attack nor be attacked in that Phase (see 7.14), even if their advance places them next to Enemy units whose battles are yet to be resolved, or who were not involved in, combat. However, advances are useful in cutting off the retreat of Enemy units whose combat has not yet been resolved.


Example: A defeated unit retreating three hexes may be followed by up to three victorious units in its Retreat Path.

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[8.0] Artillery

General Rule:

Artillery units may participate in combat from adjacent and non-adjacent hexes. The Artillery unit's Barrage Strength may be used to attack Enemy units. The Artillery unit's Final Protective Fire Strength may be used to supplement the Defense Strengths of other Friendly defending units. In either case, Artillery units need not be adjacent to, but must be within range of the defending unit. An Artillery unit may use both its Barrage Strength and Final Protective Fire Strength in a single Game-Turn. When attacked, an Artillery unit defends itself with its own Defense Strength.


[8.1] Barrage Attacks


Artillery units may attack non-adjacent Enemy units up to the extent of their Range Allowance, but they are never forced to attack an Enemy unit merely because it is within range. Artillery units are not subject to Line of Sight restrictions.


Range from the Barraging Artillery unit to the defending unit is counted by including the target hex (defending unit's hex), but not the Barraging unit's hex.


Artillery units may only attack a single Enemy-occupied hex when barraging, except when making a combined attack with other units attacking from adjacent hexes (see 8.2).


Barraging Artillery (Artillery attacking from a non-adjacent hex) suffer no Combat Results; they are never destroyed or retreated as a result of their own attacks. Of course, other units cooperating with the Barraging Artillery units from an adjacent position would be affected by Combat Results.


In attacks made solely by barraging(non-adjacent) Artillery and/or Ground Support Strength, only Combat Results of D2, D3 and De affect the defending unit.

[8.2] Combined Attacks


Artillery units may attack alone, in concert with other Barraging Artillery and/or Ground Support, or in concert with any Friendly units making adjacent attacks, adding their bombarding Combat Strength to the attack. These attacks are called Combined Attacks.


When Friendly units are attacking adjacent Enemy units in more than one hex, the Barraging Artillery units need be within range of only one of the defending units to add their Barrage Strength to the attack.

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[8.3] Adjacent Attacks


When adjacent to an Enemy unit, Artillery units must participate in an attack against adjacent Enemy units. In making this attack, the Artillery unit uses its Barrage Strength.


When attacking from an adjacent hex, Artillery units may attack as many units as they are adjacent to, but may not attack non-adjacent units.


Artillery units attacking from an adjacent hex must suffer all the Combat Results of their attacks.

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[8.4] Final Protective Fire


A non-Phasing Artillery unit, which has not yet been subject to a successful attack in the current Combat Phase, had suffered no adverse Combat Results in the previous Combat Phase, and is not adjacent to an Enemy unit, may use its Final Protective Fire Strength (FPF) to supplement the Defense Strength of a Friendly unit which is under attack. If a non-Phasing Artillery unit has been displaced, had suffered a Combat Result in the previous Combat Phase, or is adjacent to an Enemy unit, it may not use its FPF during the current Enemy Combat Phase.


The Friendly defending unit receiving Final Protective Fire must be in range of the Artillery unit providing the FPF. This range is computed to the hex occupied by the defending unit [the Friendly unit], not to the hex occupied by the attacking unit [the Enemy unit].


FPF Strength Points are simply added to the Defense Strength of the unit receiving Final Protective Fire.


When an Artillery unit supplies FPF, it neither benefits nor suffers from the Combat Result.


FPF may not be used to supplement the Defense Strength of a Friendly unit which is under attack solely by Enemy Artillery (either adjacent or non-adjacent) and/or Ground Support.

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[8.5] Defense

When an Artillery unit is attacked In any fashion, it uses its Defense Strength, not its FPF.

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[8.6] Terrain Effects


An Artillery unit may use its Barrage or FPF Strength anywhere within its Range Allowance, regardless of intervening terrain or units (either Enemy or Friendly).


Defending units benefit fully from the terrain in the hex they occupy when attacked by Artillery (regardless of range). Defending units do not receive any hexside benefits if attacked solely by Artillery and/or Ground Support. Defending units do receive hexside benefits if they are subject to a Combined Attack involving adjacent non-artillery units, all of which are attacking across the terrain hexside type in question.

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[9.0] Ground Support

General Rule:

Some Artillery and/or Air Power in the game is not represented by units, but rather by the allocation of Ground Support Points, on a Game-Turn by Game-Turn basis. These Points are allotted on the Turn Record/Reinforcement Track. The game system records the allocation and expenditure of Ground Support Points. Ground Support Points are presumed to come from off the playing area and do not have any range limitations (unless otherwise stated in the Exclusive Rules).


Ground Support Points may be used during any Combat Phase, almost exactly as if they were Artillery, and can function as Barrage or FPF. Example: A Player has 10 Ground Support Points allocated in a given Game-Turn. When he is the Phasing Player, he may use these Points as Barrage Strength Points. When he is the non-Phasing Player, he may use these same Points as FPF.


[9.1] Restrictions and Prohibitions


One Ground Support Point equals one Artillery Strength Point (both Barrage and FPF).


A Player may assign all available Ground Support Points to one target unit, or he may split them up between as many targets as he sees fit.


Ground Support Points have unlimited range. They may attack any Enemy unit on the map.


Ground Support may not be accumulated from Game-Turn to Game-Turn. If they are not used in the Turn allocated by the Track, they are lost.


Ground support points may not be used to attack on their own. They can only be used to support an existing attack or defence of a ground unit.

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[10.0] Japanese Massed infantry ("Banzai") Attacks

General Rule:

The Japanese Player may elect to convert any regular combat involving infantry/engineer units into a massed infantry ('Banzai') attack. See the 'Banzai' option on the top game menu bar.


The Japanese Player declares that a regular attack will become a 'Banzai' attack before the die is rolled (By pressing the Attack button) for that combat. He then doubles the Attack Strength of all Japanese infantry and engineer units involved in that combat. The die is rolled and cross-referenced with the new Differential column on the CRT and the result is applied as in normal combat. At this point, the Japanese Player must remove infantry and engineer units whose total printed Attack Strength equals the printed Defense Strength of the American unit. These units are destroyed to reflect the suicidal nature of the tactics employed in such an attack.


[10.1] Effect


The Japanese Player may double only the Attack Strength of infantry or engineer units involved in the combat. Armor or Artillery may not be doubled in this type of attack.


When removing units whose Attack Strength equals the Defense Strength of the American unit, the computer system will remove infantry and/or engineer units first.  If there are not enough units of this type to meet the requirement, then he must remove armor and adjacent Artillery units in that order.  Where there is a choice of units to remove the computer system will remove the least number of Japanese units that equal or exceed the required strength point loss.


Barraging Artillery units may not be removed to meet the exchange requirements of these rules.

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