Arimaa/Attacking/Positioning

Squares adjacent to the trap are key to any trap attack. For simplicity, examples will have Gold attacking the c6 trap. Naturally, the same principles apply when Gold attacks f6, or when Silver attacks c3 or f3.

Positioning the elephant

While attacking the c6 trap, the gold elephant would most often want to occupy d6. On b6 or c7, an attacking elephant would be decentralized and might become blockaded. In most cases, an attacking elephant would rather be on d6 than on c5:

• A d6 gold elephant prevents a fork between c6 and f6.
• A d6 gold elephant blocks silver defenders arriving from the east.
• A d6 gold elephant impedes the forward development of silver pieces in the center.
• A d6 gold elephant can easily move to e6 to defend or attack the f6 trap.
• Blocking Silver out of d6 could later compel her to occupy c5, which is not ideal for a trap defender. Any non-elephant silver piece on c5 could be pushed or pulled to c4, and Gold might then have threats in both c3 and c6. To avoid this, the silver elephant might defend its home trap, but then Gold might create a threat elsewhere and overload Silver.

Nevertheless, a trap attack can be effective even with the attacking elephant on c5, where it might prefer to be if something is occurring around c3.

Once on d6, an attacking elephant should stay in place until it is not needed there, or until it is more needed elsewhere. If the attacking elephant leaves the trap, other attacking pieces could then be at risk in that trap. Even if the gold elephant moves from d6 to c5, that might allow Silver to fork a piece between c6 and f6.

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h

Diagram 1: Silver to move can do little to counter Gold's attack on c6.

Diagram 1 shows an ideal attack. No matter which side has the next move, Gold has firm control of the c6 trap. Notice these positional features:

• The silver elephant would need more than one turn to reach c5.
• The gold elephant stands between the silver camel and the advanced gold horse.
• The a5 dog is the only silver piece that could immediately reach c5 (with da5e ra8s ra6s db5e) and thus become a second silver defender of c6. However, a gold horse could then push or pull the dog to c4, creating a double threat while the gold elephant remained on d6.
• Silver cannot scatter in time to prevent a c6 capture; even if Silver could do so, Gold could then advance a rabbit on the c-file, threatening goal.
• If the gold elephant were instead on c5, Silver could move her e7 horse to d6 and also move her elephant a square west.

Silver to move cannot occupy b6 or d6, and cannot safely occupy c5. Silver's forces are quite unbalanced, but would be in better shape if the d6 square were accessible.

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h

Diagram 2: With the gold elephant on c5 rather than d6, c7 is not a safe square for a gold attacker.

By contrast, Gold is very weak in diagram 2 with Silver to move. Silver can play ed5nns Hc7e, freezing the gold horse and preparing to fork it between c6 and f6; this is a risk of having an attacking piece on c7 without the attacking elephant on d6. As an aside, Silver should probably go after the c7 horse immediately, so that Gold can't re-align around c6. The attack on f3 can wait, and will be more effective if Silver already has a threat elsewhere.

Although an attacking elephant should generally not be decentralized, there are exceptions. If an attacking elephant can move through the trap and push the defending camel to a middle row, as occurred on 21g of this game, the double-threat may justify temporarily marginalizing the elephant. In other cases, the gold elephant might go to c7 to unfreeze a b7 hostage. A goal threat might sometimes be strengthened by an elephant on or beside the goal line. Such moves require great caution, however, as an elephant can often become blockaded in a corner. In this game, Silver may have felt safe placing her elephant on c2 and then c1, as Gold's forces were depleted. However, Gold used silver pieces to help box in the silver elephant.

Key squares

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h

Diagram 3: Gold cannot gain access to b6 or c7.

A successful opening attack usually gets the attacker's horse or camel safely onto a decentralized key square. In this game, Gold attacked in the west, but Silver kept b6 and c7, which Gold is now blocked from. If the gold elephant leaves the trap, Gold will lose material; Silver can now overload Gold, whose western attack has backfired. For most of the game, rabbit advances must be connected to the activity of strong pieces other than the elephant.

a b c d 8 7 6 5 4

Whether an attacker is better on b6 or c7 depends on the position:

• A gold attacker on b6 is freer to retreat if it becomes necessary to abandon the attack.
• A gold horse on b6 denies the silver horse its ideal defensive square. In the diagram at left, the a6 silver horse is passive.
• A gold attacker on b6 restricts the development of silver pieces in the west, securing a space advantage for Gold.
• An attacking gold horse might be taken hostage by the silver camel, which could often reach and hold c7 more easily than it could b6.
• A gold attacker on c7 might be pulled toward the f6 trap.

On the other hand:

• A gold attacker on b6 might block other gold pieces, whereas a gold attacker on c7 would not stop further gold advances on the flank.
• A strong gold piece on c7 would block silver reinforcements coming from the east.
• A gold attacker on c7 could weaken the silver goal line.
• Often, a b6 attacker cannot move and then hope to return to b6; at left, the a6 silver horse is ready to reclaim b6 if the gold horse moves. Were the gold horse on c7, it might be able to step away and return later, meaning that Gold could free his elephant while retaining a long-term threat to c6.
• A gold piece on c7 could go east if Gold decides to attack f6.

A b6 attacker might later move to c7. Above, Silver blocks that by occupying b8, a7, b7, c7, c6, and c5.

Once Gold has firm control of b6 or c7, he might swarm the trap, perhaps freeing the gold elephant while further restricting the silver elephant. If an elephant does not defend its besieged home trap, the attacker might quickly clear space for a goal.

Positioning a rabbit

a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h

Diagram 4: Silver to move could push the gold rabbit onto c6 and delay any capture by Gold.

While rabbits can participate in a trap attack, a friendly rabbit may be a liability for a trap attacker trying to capture material. In diagram 4, it might appear that Silver to move cannot prevent a loss in c6. However, Silver has one "nuisance move" that will delay a capture: hd6s Rc5n hd5we would leave the gold rabbit on c6 and the silver horse on d5, precluding any one-turn capture by Gold. On d5, the silver horse would be less vulnerable than it might seem: if the gold camel went to d6, Silver would have a chance for a camel trade. If the gold camel went to c5, Silver could then place defenders on both c7 and d6. If the gold camel stayed away from the silver horse, the horse might go south and start something. If not for the gold rabbit on c5, Silver could not have avoided an immediate loss of at least a dog. Gold still has a strong position as long as he is careful with his camel, but this shows how one misplaced rabbit can be exploited by the opponent. If both sides were actively attacking, such a delaying tactic could prove decisive. Since a rabbit cannot back out of a trap, it is often best to avoid placing a rabbit next to a trap in which one hopes to make captures.