Arimaa/Distribution of Force

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Neither gold horse can fight either silver dog. (game)

An important element of Arimaa is the overall distribution of pieces. One basic concern is efficiency: one should use the weakest piece possible for any particular job, sparing stronger pieces for other duty. In the current position, Silver would gain no further advantage by having a horse on g3, so the silver dog is efficiently placed there. Another basic concern is activity: strong pieces should be kept flexible and available for duty. The b2 gold horse is passive, since its development is blocked and it cannot easily do anything useful. The a3 gold horse is less blocked, but still poorly placed, as it is very far from both silver dogs. With an active gold horse nearby, a silver dog could not easily hold a key square.

Although pieces are often passive because they are blocked in at home, even a functional advanced piece is passive if it does not usefully fight for trap control.

Having the strongest local piece is often crucial. For example, a camel and dog might take control of a trap against two horses, but not vice versa. The strongest local piece can also help with goal attack, goal defense, mobility fights, etc.

The army which is better distributed overall will have the advantage.

Alignment[edit]

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Silver is dominating the entire board (game).

Alignment refers to the general positioning of the army relative to the opposing army. An efficient alignment is one where each piece dominates the next-weaker opposing piece, while avoiding the next-stronger opposing piece. Elephants should attack camels, camels should attack horses while avoiding elephants, horses should attack dogs while avoiding camels, etc.

In the diagram, Silver has a large alignment advantage: the silver elephant is fighting the gold camel, the silver camel is fighting gold horses, and the c2 horse is fighting a gold dog. The silver camel and c2 horse are both strongest local pieces, while Gold does not have the strongest piece in any area.

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The silver elephant and camel ignored the gold horse, letting it create a strong goal threat.

A poor alignment can lose a nearly won game. In this endgame, Silver had a camel advantage, but still let the one remaining gold horse beat her. When it went north on 36g, Silver took no notice. With nothing to stop the gold horse in the northeast, it created a one-turn goal threat on 38g. At that point, Silver had only one way to stop it, and that left her elephant on the f3 trap square. The elephant was lost.

Balance[edit]

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Silver needs a dog on each wing.

It is usually best to have some strength on each wing. In the position at right, from this endgame, the strongest remaining pieces are the elephants, horse, and dogs. Gold has split his horse and dog; the dog has just advanced in the west, and the horse is poised to advance in the east. The silver elephant cannot fight both at once, but would do best to confront the horse, which could otherwise dominate the east. Silver would however be left vulnerable in the northwest if the silver elephant went east.

Having both silver dogs in the east is pointless; a second dog is not needed to defend f6, and doesn't improve Silver's prospects for taking over f3. The e7 dog should move west, to counter the gold dog and delay any Gold takeover of c6. In the actual game, Silver left both dogs in the east, and soon got into trouble. Had Silver balanced his dogs, he would have had time to counterattack in the east.

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In this game, the silver elephant is stuck defending a horse and dog, but the gold elephant is stuck defending goal.

It is also often important to balance weak pieces, which are vital to home defense and to goal threats. With three gold pieces already gone, and eleven gold pieces tied up in the hybrid frame–hostage–partial elephant blockade, Gold is very weak in the west. The gold elephant is currently stuck defending goal, so the silver camel is free to disrupt Gold's eastern position. Using one's elephant to defend against rabbits is extremely inefficient.

Centralisation[edit]

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The gold camel cannot safely advance without the support of the gold elephant. (Game)

Ideally, an elephant should be able to quickly get anywhere it might be needed. Thus it should stay fairly centralized, unless it could decidedly improve its side's overall position by going to the outskirts.

The diagram at right illustrates the tactical dangers of elephant decentralisation. The gold elephant has gone far away from f3, allowing Silver to start an attack there despite the gold camel's presence; until the gold elephant comes east, the gold camel cannot safely chase the g3 horse. If Gold played Me2n De1n Me3e De2n, Silver could push the gold camel to f4 (De3s ee4s Mf3n ee3e), where it would be doomed to capture in f6. This would not work for Silver were the gold elephant in the centre.

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Gold pieces can move through the center. (Game)

Control of the center itself is also important; pieces blocked or threatened in the center will have a harder time navigating the board. If one elephant becomes marginalized, the opponent will likely have greater central control. Such is the case in the diagram at left: any silver piece that goes into the centre risks being forked between c3 and f3, whereas gold pieces can move much more freely.

Shared control of an away trap may be an opportunity to take central control; if the opponent has complete control of only one trap, pieces in the center are often safe. It is sometimes even possible to blockade the center.

Development[edit]

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In this game, Silver's advantage is partly a result of Silver's better development.

When one army is more advanced than the other, the more advanced army has more room to maneuver and gets the first chance to attack. The opponent must then divert resources to defense, perhaps allowing the advanced army to develop further.

In the diagram at right, each side is missing a camel and horse; with fewer pieces to threaten capture, advanced pieces are safer. In the opening, advances would tend to be riskier, though it is usually good to have advanced pieces on a wing where one may get a strong attack—for instance on one's camel wing if camels are on opposite wings in the opening. In a slow opening, the attacking potential of advanced pieces may be outweighed by the risk of capture in away traps.

Of course, the need for development must be tempered by the need to defend one's home traps and goal line. If direct home defense is sparse, the advanced army must stop threats from getting that far.

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Silver's advanced pieces stop Gold from advancing. (Game)

In the position at left, the board is still full, but Silver has developed to a point where Gold would have trouble advancing anything. Any western Gold advance would be slow and, due to Silver's potential goal threat, dangerous. Any gold piece that advanced in the east would risk quick capture in f6. With the situation in the west, the gold elephant can scarcely afford to go east.