Threefold repetition
From Chesspedia, the Free Chess Encyclopedia.
In chess, the threefold repetition rule states that a player can claim a draw if the same position occurs three times, or will occur after their next move, with the same player to move, and with each player having the same set of legal moves each time, including the right to take en passant and the right to castle. The game is not automatically drawn if this happens: one of the players, on their move, must claim the draw with the arbiter.
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)
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- 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
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- 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 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 temporarily or permanently.
While the rule does not require that the position occur thrice on consecutive moves, it happens this way very often in practice, typically with one of the kings being put into perpetual check.
The clause about the right to take en passant and the right to castle is a subtle but important one. In a game between grandmasters Anatoly Karpov and Anthony Miles (Tilburg 1986), Karpov, with less than five minutes on his clock, claimed a draw by repetition after checking his scoresheet carefully, whereupon it was pointed out to him that in the first occurrence of position, Karpov's king had had the right to castle, whereas in the second and third it had not. Tournament rules stipulated that a player be penalized with three minutes of their time for incorrect claims, which left Karpov's flag on the verge of falling! By then, Miles had had his fun, and took the draw.
At various times in the history of chess, the rule has been variously formulated. In Tim Harding's MegaCorr database (a collection of correspondence chess games), the notes to a game between the cities of Pest and Paris played between 1842 and 1845 state that a sixfold repetition was necessary to claim a draw. The game went: 1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.d4 d5 6.Bd3 Bd6 7.O-O O-O 8.c4 Be6 9.Qc2 f5 10.Qb3 dxc4 11.Qxb7 c6 12.Bxe4 fxe4 13.Ng5 Bf5 14.Nc3 Qd7 15.Qxd7 Nxd7 16.Ngxe4 Bc7 17.Re1 Rab8 18.Re2 Nb6 19.Nc5 Bd6 20.N5e4 Bc7 21.Nc5 Bd6 22.N5e4 Bc7 23.Nc5 Bd6 24.N5e4 Bc7 25.Nc5 Bd6 26.N5e4 Bc7 27.Nc5 and now instead of taking the sixfold repetition draw with 27...Bd6 28.N5e4 Bc7, Paris diverged with 27...Bd3 and went on to lose the game.
Players sometimes repeat a position once not in order to draw, but to gain time on the clock (when an increment is being used) or to bring themselves closer to the time control (at which point they will receive more time). Occasionally, players miscount and inadvertently repeat the position more than once, thus allowing their opponent to claim a draw in an unfavourable position (Adams-Ponomariov, Wijk aan Zee 2005 may have been a recent example of this [1]).
