Additional rules for multiplayer chess variants

by Derick R. Peterson, 10/08/97

Derick R. Peterson created the following additional rules for multiplayer chess variants, In an effort to lessen the inherent lack of fairness and petty diplomacy problems of such a multi-player perfect information strategy games. The rules are stated in general for any n-player chess variant where more than 2 players or teams are competing to be the sole victor.

(1) Defending from multiple attackers

When one player is simultaneously threatened by k (1 < k < n) opponents, he is entitled to move up to k of his pieces during his turn subject to the following restrictions.

1. No piece may be moved more than once.
2. He may not capture more than one piece belonging to any one opponent.
3. He may not threaten or capture any more than one new piece belonging to any one opponent unless all but one of his attacks on that opponent simultaneously attack pieces of other opponents.
4. Unless he can simultaneously check or checkmate all of his k attackers, he may not use more than one of his moves to enforce checkmate on any one player even if the checkmating piece simultaneously attacks another opponent's piece.
5. None of his moves can expose his king to check even if his next move in the same turn could parry the check.

(2) Fair exchange of pieces per round

When any k players exchange pieces in the course of one "round" of moves, those n-k players not involved in the exchange are obliged to remove pieces of equal or greater value than the weakest piece involved in the exchange subject to the following restrictions.

1. No player is obliged to remove his king or any piece which exposes his king to check.
2. Here a "round" is defined to be a series of n players' turns, beginning with one player's capture of an opponent's piece.
3. The players forced to remove their own pieces may choose which piece or pieces to remove, and these pieces are not removed until their turn following the round of exchange.
4. Any player forced to remove pieces may choose to exchange a powerful piece for any of his captured pieces whose powers are a proper subset of the piece which is being exchanged. For example, a live queen can be exchanged for a captured rook or bishop but not a knight or pawn. The weaker exchanged piece must, of course, be placed on the square vacated by the more powerful hostage; note that this determines the color of a bishop taking the place of the queen, for example.

(3) Checkmate and capture of a king

1. A player is not out of the game until his King is actually captured.
2. When his King is captured, his pieces remain on the board as immovable obstacles for the remaining players to navigate. If all players agree in advance, these pieces may be captured to remove them from the board; otherwise, these obstacles cannot be captured nor removed.
3. When a player's King remains on the board, but he is in checkmate, he loses his turn until the checking piece withdraws. However, while in a checkmate freeze, except for his King that player's pieces are immune to attack from all other players.