Multiplayer Chess Rules

To clarify, consider the following example (assuming a square board without walls). The move order rotates as follows: Red, Green, Blue. It is Red's move. Red's King is on a1, Green's knight is on b4, and Blue's rook is on b8. (More realistically, these points could be the hexes QR1, QN4, and QN8 on one of the AmeriChess board variants in Red's territory. QN8 will probably lie beyond the so-called "sovereignty line".) Also, assume that no other points on the b-file are occupied, and there are no other relevant checks.

Now, Red makes his move. He plays Kb1. The move is perfectly legal because it does not expose the king to the attack by Blue's rook, for Blue's rook is blocked by Green's knight. But then Green plays Nc6. (This could still be legal in AmeriChess.) Now it is finally Blue's turn, and he find's that one of his opponent's kings is exposed. Can he play Rxb1? If he does, is that considered mate?

A related difficulty is, what happens when Green makes a move that mates Red, but blue's move allows Red to escape mate? The rules should make the point clear that a player is not mated unless a) it is his move, and he has no move that gets him out of check, or b) his king gets captured in the shuffle, as explained above. Also, a player is not stalemated unless it is his move and he has no legal moves, yet is not in check.

Still another question is, at the end of the game, when only one player has an active king left, what is each player's score? A reasonable answer might be: anyone who is checkmated gets 0; all other players have the full point divided equally among themselves. For example, if Green gets stalemated, and then Red checkmates Blue, the final score is: Red 1/2, Green 1/2, Blue 0. If all three players agree to draw while still active, the score would be: 1/3, 1/3, 1/3.

Finally, are players allowed to resign? Possible answers might be: 1) resignation is permitted only if all but one active player wishes to resign, 2) resignation is permitted only if there are only 2 players still active, 3) resignation is permitted only when the player to move wishes to resign, or when he has only one opponent remaining, 4) Resignation is permitted anytime, but when a player resigns while it is not his turn, his King remains on the board until his next turn, one of the remaining players removing it for him, and 5) resignation is prohibited. In 3), the player resigning simply removes his king as if checkmated. An example of where two players may both legitimately resign would be when Red has a King and Queen (or whatever is sufficient to mate two players), Blue has a lone King, and Green has a lone King. Red could checkmate one king after the other, no matter what his opponents might conspire to do.

Finally, the following rules could be suggested for draws other than stalemate: 1) the fifty move rule, that is, 50 times N plies since the last checkmate, stalemate, pawn move, or capture, where N is the number of players remaining; 2) three-fold repetition of the same position with the same player to move, same castling and en passant privileges, etc.; 3) unanimous agreement among all players remaining; 4) no remaining player has sufficient mating material. In 1) and 2), any player could claim the draw.

Note that some of the questions may seem to have obvious answers, but deserve clarification.

Summary of rules I would propose in answer to the above unaddressed questions:

1. Check. A player is in check whenever his King is in the line of capture of another active player's piece, provided that that line is not blocked by any piece. A player is not in check because of an opponent's piece blocked by another opponent's piece, even if it is possible that the King could be exposed before the player's next turn. It is illegal for a player to make a move that in the immediately resulting position leaves his King exposed to check.

2. Checkmate. When it is a player's turn to move, the player is in check, but has no legal move, he is considered checkmated. At his turn, the player must remove his king from the board and abstain from further participation in the game. His remaining pieces remain on the board until captured, and are considered inactive. It is legal to expose one's King to attack by an inactive piece.

3. Capturing the King. It is possible that a player's King may be exposed before his turn, without any rules being broken. It can happen that one player exposes another player's King, and the second player has an opportunity to make the capture without the player who's king is exposed having an intervening turn. Only three players need remain for this to be possible. In that case, the capture of the King shall be permitted, as would any capture. The player who's king is "caught in the shuffle" is out of the game at that point, just as if he had been checkmated, and simply does not take his next turn, his King having already been removed.

4. Stalemate. If it is a player's turn, the player is not in check, but has no legal moves, then the player is considered stalemated. As in the case of checkmate, the stalemated player must remove his King from the board and remove himself from the game. However, the stalemated player does participated in the scoring at the end of the game.

5. Resignation. If at any point during the game, a player wishes to resign, he must inform his opponents. He may leave the game at this point, but does not remove his King unless it is his turn when he resigns. Rather, his King remains on the board until his next turn, unless it incidentally happens to be captured in the shuffle. When it comes to pass that the player who has resigned should take his turn, and his King remains, his King shall at that point be removed, and that will officially be his last turn. The player who resigns may remain present to see to it that his King is removed, if he wishes; Otherwise, the player who moves after him must look after his King. Rather than using a verbal notification, a player may signal his resignation during his turn to move by simply removing his King. If a player does not wish to wait for his turn, he may simply lay his King flat, stand his King back up, and walk away.

6. Offering a draw. When a player feels that none of the remaining player's can make any progress, he may offer a draw. His offer remains valid until the opponent preceding him has made his move, making it his turn. His offer ends the game if all of his opponents agree.

7. 50-move rule. A move is a complete cycle of turns made by each player, whether they be ordinary moves, King captures, or King removals. If 50 moves are made without a pawn move, a capture, a checkmate, a King removal, a stalemate, or any move affecting en passant and castling privileges, any player can claim a draw by his next turn by the 50-move rule. The 50-move rule can only be extended in certain exceptional positions involving two remaining players.

8. 3-fold repetition. If the same position occurs three times with the same players active, the same player to move, and the same castling and en passant privileges, then any player can claim a draw by repetition before his next move.

9. Verification of claim. When a player claims a draw by the 50-move rule or by repetition, all players present, and possibly a director, must examine the game to verify the claim. If the claim proves true, the game shall end with all players remaining participating in the draw.

10. Insufficient mating material. When the material remaining is so low that checkmate or King capture is impossible regardless of what all players may conspire to do, and this is obviously the case, the type of position having been clearly categorized, then the game shall end in a draw. The situation in which all active players are left with lone Kings should be recognized as insufficient mating material. Otherwise, what is sufficient to mate may depend on the number of players remaining, the shape of the board, and the manner in which the remaining pieces move. Except for lone Kings, any multi-player situation is likely to be sufficient. For example, Suppose the board is the ordinary square board, Red has King and Bishop, and Green and Blue each have a lone King. It is then possible that Red and Green could conspire to checkmate Blue, and if Red and Green cooperate, the mate could even be forced!

11. End of game. The game ends when either 1) there is only one player left, 2) all remaining players agree to a draw, 3) a claim of a draw by the 50-move rule or 3-fold repetition is proven, or 4) there occurs a draw by insufficient mating material.

12. Scoring. At the end of the game, the game shall be scored as follows. Any player who is checkmated, who's King gets captured, or who resigns gets zero. All other players, having either been stalemated, or remaining active to the end, get a score of 1/N, where N is the number of such players.

13. Timing. If the game shall ever be played with clocks, which is quite possible over the internet, then a player who's time expires must have his King removed at his next turn, just as if he had resigned. His score will of course be zero.