For simplicity, many examples below will assume that Gold is attacking the c6 trap. Naturally, the same theories apply equally in all four quadrants.
Positioning the elephant
The attacking elephant should usually remain centralized. Moving the elephant to a square such as b6 or c7 will usually lead to a failed attack or even a blockaded elephant, though there are a couple of exceptions discussed below. In most cases, an attacking elephant would rather be on d6 than c5:
- The elephant is the only friendly piece which can safely occupy d6, since any other piece would be vulnerable to capture in f6.
- If no enemy defender can occupy d6, the c6 trap is vulnerable unless the enemy elephant stays nearby; if the enemy loses b6 or c7 in addition to d6, having nothing on c5 would cede the c6 trap, but any non-elephant piece they place on c5 could then be threatened in both c6 and c3.
- A d6 elephant keeps a gold piece on c7 safe from being taken as a central hostage.
- A d6 elephant blocks silver defenders arriving from the east.
- A d6 elephant impedes the forward development of silver pieces from their back ranks.
- A d6 elephant can easily move to e6 to defend or attack the f6 trap.
However, c5 is an acceptable square for the attacking elephant, and may be better if, for instance, there is an important fight happening around c3.
Once an attacking elephant occupies d6, it should often stay there to deny silver pieces that square, until a specific opportunity appears elsewhere (such as the e6 square during a double-attack).
The ideal situation in diagram 1: The gold elephant and horse have taken control of the c6 trap with devastating efficiency. Notice all of the following features of the position:
- The silver elephant, usually the key defender against an elephant and horse attack, is more than four steps away from the c6 trap.
- The silver camel, also highly effective against an elephant and horse attack, is on the wrong wing.
- The a5 dog can reach c5 with da5e ra8s ra6s db5e, but Gold can easily push the dog to c4, with double-trap threats at c3 and c6.
- The defender cannot scatter all pieces away from the c6 trap and, even if Silver were able to do so, it would allow Gold to begin a highly potent rabbit advance such as Rd1n Rd2n Rd3w Rc3n.
- If the gold elephant were on c5 rather than d6, then Silver could temporarily defend with two steps such as he7s he6w, and still bring their elephant toward the northwest quadrant with Rf4s eg4w.
Two important keys to this powerful gold attack are the combination of b6 and d6 attackers that prevent the nearby silver pieces from sharing control of the trap, and the lack of balance in the silver army, with its four strongest pieces all on the same wing.
By contrast, the position in diagram 2 will turn into a disaster for Gold with Silver to move. Notice that Silver can immediately play ed5n ed6n ed7s Hc7e, holding the gold horse hostage. As discussed in another chapter (provide link), a hostage that is frozen by an elephant on d7 is very difficult to protect. For example, if Silver plays ed6s hd7s on the subsequent move, the horse will be forked between the c6 and f6 traps. This illustrates both the danger of a hostage piece in the d- and e-files and the importance of having an elephant on d6. As an aside, Silver should not continue with the camel and horse attack in the southeast quadrant until first holding the gold horse hostage on d7 - otherwise, Gold will likely retreat the c7 horse from danger while still having sufficient time to defend the southeast trap.
Although the elephant should generally not be decentralized during an attack, there are exceptions. If there is a silver camel on b6, then it could be worthwhile to temporarily place a gold elephant on b6 in order to push the camel south. This could eventually lead to a camel hostage near the c3 trap. Also, if Gold has a powerful goal threat in the northwest quadrant then it may be worthwhile to decentralize the elephant and move it onto the 7th or 8th rank. Be very, very careful when doing so, however, as an elephant can easily become blockaded if it ventures into the corners. Use a weaker piece to support a rabbit advance on the perimeter whenever possible.
Controlling the b6 and/or c7 squares is vitally important for the great majority of Arimaa attacks. A strong piece should be used to secure these important squares; in the opening, usually a horse or camel. To see why control of b6 and c7 is so important, the reader should study diagram 3 from this game. Gold had planned to aggressively advance pieces on the west wing before gaining control of either b6 or c7. However, Silver was able to keep Gold's strong pieces away from key squares, and now the gold elephant is pinned to d6 with no prospects for continuing the attack (other than a futile attempt to control c5). However, any piece that stands on c5 is at risk of being pushed to e5, creating a double-threat certain to result in a material gain for Silver. Eventually, Gold had to abandon the c6 square and suffered through an inferior position in the middlegame. It cannot be stressed enough that advances of weak pieces (especially rabbits) need to be connected to a threat to control b6 or c7 with a strong piece.
Once the attacker has firm control over key squares, it becomes possible to either flood the trap with rabbits, cats and dogs or, if the silver elephant is not in the vicinity, it may become possible to begin capturing material around the trap.
Whether an attacker is better on b6 or c7 depends on the position:
- An attacker on b6 is freer to retreat if it becomes necessary to abandon the attack.
- A horse on c7 is vulnerable to being hostaged by the silver camel if the camel is in its back ranks.
- A horse on b6 denies the silver horse its ideal defensive square. In the diagram at left, the a6 silver horse is passive.
- An attacker on b6 restricts the development of silver pieces in the west, securing a space advantage.
On the other hand:
- Moving an attacker to c7 makes room for a second attacker to come into b6, possibly framing a silver piece on c6.
- A gold piece on c7 prevents Silver from bringing reinforcements from the east. This is especially important when pursuing a goal attack.
- It is usually easier for a c7 piece to scatter, giving the gold elephant some freedom while retaining long-term shared control. At left, the gold horse cannot move without ceding trap control and leaving the gold rabbits vulnerable. Were the horse on c7, it might be able to move—for instance to c8—and return to a key square later.
After a trap is fully controlled, the c7 square will often become more important than the b6 square, since Silver will counterattack from the east.
Positioning a rabbit
A rabbit can be a very useful piece during a swarm attack, but can often be a liability for the attacker if the objective is to capture material. In diagram 4 with Silver to move, it might appear at first glance that Silver cannot prevent the loss of material at the c6 trap. However, there is one "nuisance move" at Silver's disposal that will delay a capture: hd6s Rc5n hd5w hc5e. If Gold responds with Rc6e Mc7s Mc6s Db3n then Silver will be able to counter with dc8s cd8s Rd6e cd7s. Although Gold should be able to win material in this tactical melee, the game will not proceed as smoothly as initially expected. This loss of time by Gold may not be a decisive factor in this game, but in many open, tactical games it is crucial to prevent nuisance or delaying tactics by the defender. Note that Gold could have immediately won material if not for the rabbit on c5. Due to the weakness of the rabbit and its inability to retreat, rabbits are much better employed for goal threats and blockades, and should be placed near an important trap only with care.