Arimaa/Introduction to Strategy/Early Ideas

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Early Arimaa players had no blueprint, and could only experiment. The object was to get a rabbit to goal first, but was it better to aggressively go for it, or bide one's time and focus mainly on home defense? If defense proved most important, would Arimaa become a stalemate?

Direct Goal[edit]

The most direct strategy in Arimaa is to try to rip a hole in the goal line and then march a rabbit through. If both players go this route, the game turns into a race; if a race begins right away, it may favor Gold since Gold goes first. Fortunately for Silver, racing is not one's only option.

In the opening, it is easy enough to defend against a direct onslaught; a full army can prevent attackers from simply tearing through. Other than the elephant, attacking pieces risk capture in the defender's home traps. The attacking elephant can protect one trap, or perhaps help threatened pieces retreat, but having one's elephant on defense is not a promising way to force a goal.

As long as there is no real opening in the goal line, it is futile to advance a rabbit for the purpose of reaching goal. Remember that an advanced rabbit can't retreat, and thus is quite vulnerable to capture. Generally speaking, it would be extremely wasteful to use one's elephant to protect a rabbit.

In short, going for a direct goal is a poor strategy which can quickly set one back. Nevertheless, a goal path must eventually be cleared somehow.

Capture[edit]

The next obvious strategy is that of capturing pieces, though that is not straightforward either. An opponent committed to defense will have two or three pieces next to each home trap, so an elephant alone can't force a capture in an enemy trap. Even if attackers try to overwhelm a particular trap, the defending elephant can protect it and likely turn the tables on an attacker.

A safer approach would be to use the elephant to drag an enemy piece toward one's own home traps. This seems promising, since a piece could be forked between traps, and it would be difficult for the opponent to defend both. However, a defending army can make it hard to pull pieces down, since pieces can unfreeze each other and (except for rabbits) retreat. It is easiest to drag down a piece on a flank, but then it could likely only be threatened in one trap, which the defending elephant could stay beside, protecting that trap while also blocking the path to the attacker's other home trap.

The key to progress is to make threats around two different traps. The enemy elephant can only defend one, and any other piece which tries to prevent a capture might be captured itself. It must also be kept in mind that one's own elephant can only defend one trap at a time, and that an elephant which stays next to a trap is quite limited.

When a threat is in place, an important question is who has the strongest free piece. For example, if the gold elephant corners the silver camel, and the silver elephant must stay next to a trap to save its camel, the gold camel is the strongest free piece, if in fact that camel is still on the board and able to move around. The gold camel could then create a second threat, which only the tied-up silver elephant or camel could defend against.

That configuration became known as a camel hostage. Once players realized the problems with direct goal or capture, camel hostages became quite popular. Once again, however, it is hard to directly force this, since a camel can stay at home where it has friendly support. Thus one shouldn't actively try to force a camel hostage, unless the enemy camel has already advanced. One benefit of advancing one's elephant in the center is that it can effectively cut off the enemy camel from most of the board. A horse might then safely advance on the wing where the enemy camel can't go; the enemy elephant could take the horse hostage, but a horse-by-elephant hostage is not usually an advantage. If the enemy elephant stays beside the horse, the friendly camel can then advance on the other wing, while the enemy camel is still quite limited by the centralized friendly elephant, which could abandon its horse but capture that camel should it expose itself.

With one's elephant advanced in the center and another strong piece advanced on a wing, one can begin to form capture threats in both traps on that wing. Weak enemy pieces can be pulled or flipped toward one's home trap, and if the enemy elephant defends that trap, its own home trap will be vulnerable. Moreover, one can advance pieces on the other wing; if the enemy elephant goes after them, the centralized friendly elephant can quickly come to their defense, while the enemy elephant no longer defends either trap on the first wing.

Elephant mobility[edit]

A recurring theme in Arimaa strategy is elephant mobility. Sometimes an elephant gets blockaded, but more often it is restricted by the cost of leaving a particular trap. If one elephant is even slightly more free than the other, this advantage can quickly snowball.

Camel Hostage