Epaminondas is an abstract strategy board game invented by Robert Abbott and originally introduced in Sid Sackson's A Gamut of Games as Crossings. While the original version used an 8x8 checkerboard, the current game uses a 12x14 board and different rules for capture. It is named after the Theban general Epaminondas who made use of phalanx strategy, and the concept of the phalanx is integral to the game.

In the game, a phalanx is defined as a horizontal, vertical, or diagonal line of stones of the same colour, with no empty spaces or enemy stones between them. An isolated stone could be considered a phalanx of one, but officially all phalanxes consist of two or more stones. Note that a stone may belong to more than one phalanx, depending on the direction considered.

The initial board setup is as follows:

White moves first; turns alternate afterwards.

The rules are as follows:

1. A player may move a single piece one space in any direction, as a king in chess.
2. A player may, instead, move a phalanx any number of spaces equal to or less than the number of pieces in the phalanx. They must all move in the same direction, and that direction must be along the line of the phalanx. A phalanx of three stones along a diagonal may move three, two, or one spaces along that diagonal, and so on.
3. A player does not have to move an entire phalanx; they may split it into two pieces, as long as the subset moved is continuous and only moves, at most, as far as its length.
4. A phalanx may not move through or across pieces of the same colour.
5. The head piece of a (two-piece or more) phalanx may land on a single enemy stone; it is captured. Similarly, any phalanx's head piece may land on the head of an enemy phalanx whose size is strictly smaller; the entire enemy phalanx is captured.
6. Capture is not compulsory.

If, at the start of their turn, a player has strictly more pieces on the row farthest from them--their opponent's home row--than the opponent does, that player wins. This allows an opponent the chance to capture some of the offending stones on the turn after an incursion.

To keep the game from ending in a draw due to copycat moves, there is an additional rule: no player may move a piece onto their opponent's home row if that move creates a pattern of left-to-right symmetry on the board.

Epaminondas can be played by email, using Richard Rognlie's Play-By-eMail Server.

References

• Schmittberger, R. Wayne, New Rules for Classic Games. ISBN 0-471-53621-0
• Epaminondas, http://gamerz.net/~pbmserv/epaminondas.html