I've heard of a rule where if the same move sequence is repeated 3 times (6 moves total) the game ends in a stale mate.
Is this a de facto rule or a convention adopted outside the formal rules?
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3 Answers
It's a rule, from Wikipedia:
The relevant rule in the FIDE laws of chess is 9.2, which reads:
The game is drawn, upon a correct claim by the player having the move, when the same position, for at least the third time (not necessarily by sequential repetition of moves)
a. is about to appear, if he first writes his move on his scoresheet and declares to the arbiter his intention to make this move, or
b. has just appeared, and the player claiming the draw has the move.
Positions as in (a) and (b) are considered the same, if the same player has the move, pieces of the same kind and colour occupy the same squares, and the possible moves of all the pieces of both players are the same.
Positions are not [considered to be] the same if a pawn that could have been captured en passant can no longer be captured or if the right to castle has been changed. (FIDE 2005, Article 9.2)
While the rule does not require that the position occur thrice on nearly consecutive moves, it happens this way very often in practice, typically with one of the kings being put into perpetual check. The intermediate positions and moves do not matter – they can be the same or different. The rule applies to positions, not moves.
Also note that the draw has to be claimed, it's not automatic.
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3Beat me to it. I think it's interesting that it's positions, not moves, and that it has happened in world championship matches: "The seventeenth,[1] eighteenth,[2] and twentieth[3] games of the 1972 World Championship match between Bobby Fischer and Boris Spassky were declared draws because of threefold repetition, although the twentieth game was an incorrect claim". If that doesn't make it a legitimate rule I don't know what could! Aug 11, 2011 at 16:24
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@thesunneversets, Yeh, I got hosed once in a tournament bigtime because I thought it was moves. Aug 11, 2011 at 16:25
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1The key is "the possible moves ... are the same." That takes into account the conditions about pawns and castling. I like to think of the rule as "Stop repeating those moves: it's boring." Aug 11, 2011 at 18:16
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4Previously, a draw could only be claimed if the same sequence of moves occurred three times. The rules were changed after World Champion and mathematician Max Euwe used the Thue-Morse sequence to show that, in theory, a game could go on infinitely long without ever repeating the same sequence of moves. Of course, since there are only finitely many positions, if a game goes on infinitely long then some position will have been repeated three times. Aug 11, 2011 at 22:44
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Interesting that the castling right is included in the things that must be the same. Aug 31, 2011 at 17:49
This is a real rule. Though the wording is a bit different. It doesn't refer to moves, but rather to positions. If the exact same position occurs three times during a game, it may be declared a draw. The positions do not have to occur in succession and every figure has to be in exact same spot.
Wikipedia: Threefold Repetition
Note the following interesting addendum:
In chess, in order for a position to be considered the same, each player must have the same set of legal moves each time, including the possible rights to castle and capture en passant.
Since the rights to capture en passant or castle can possibly vanish, this means that positions that look exactly the same, might not be for the purpose of this rule.
Terminology clarification: the three-fold repetition of position is one of the ways for a game to be drawn. A stalemate (where an opponent has no legal moves on his turn) is another way for a game to be drawn. Other ways to draw: 1) when neither side has sufficient mating material (like only kings left on the board, or one side has only a bishop or only a knight); 2) 50 moves have passed without a capture or pawn move; 3) mutual agreement of the players.
