Threefold repetition


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. The repeated positions do not need to occur in succession. The reasoning behind the rule is that if the position occurs three times, no real progress is being made and the game could hypothetically continue indefinitely.
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 en passant. Positions are considered the same if the same type of piece is on a given square. For example, if a player has two knights and the knights are on the same squares, it does not matter if the positions of the two knights have been exchanged. The game is not automatically drawn if a position occurs for the third time – one of the players, on their turn, must claim the draw with the arbiter.
Similar rules exist in other abstract strategy games such as xiangqi and shogi.

Statement of the rule

The relevant rules in the FIDE laws of chess are summarized as:
Although a threefold repetition usually occurs after consecutive moves, there is no requirement that the moves be consecutive for a claim to be valid. The intermediate positions and moves do not matter – they can be the same or different. The rule applies to positions, not moves.
It is popularly thought that perpetual check is a draw, but in fact no such rule exists. Perpetual check is in fact a tactic to force a draw by repetition.
If the claim for a draw is incorrect, the opponent is awarded an extra two minutes and the game continues. Unreasonable claims may be penalized under rule 11.5, which forbids distracting or annoying the opponent. Even if the claim is incorrect, any draw claim is also a draw offer that the opponent may accept.

Fivefold repetition

From 1 July 2014, the fivefold repetition rule was introduced. This is related to the threefold repetition rule in that it looks at in the same specific sense how many times a position occurs. The fivefold repetition rule states that after five occurrences of the same position the game immediately ends in a draw regardless of whether or not a player has made a claim. If the arbiter observes a fivefold repetition, they are required to step in and enforce the draw.

Examples

The seventeenth, eighteenth, and twentieth 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.

Fischer versus Petrosian, 1971

In the third game of the 1971 Candidates Final Match between Bobby Fischer and Tigran Petrosian, Petrosian accidentally allowed the position after 30.Qe2 to be repeated three times. Play continued:
and then Fischer wrote his next move
on his, which is the third appearance of the position with Black to move, and he claimed a draw. At first Petrosian was not aware of what was going on. Incidentally, this was the first time a draw by threefold repetition had been claimed in his career,,. This also illustrates that the intermediate moves do not need to be the same – just the positions.

Capablanca versus Lasker, 1921

As noted above, one of the players must claim a draw by threefold repetition for the rule to be applied, otherwise the game continues. In the fifth game of the 1921 World Chess Championship match between José Raúl Capablanca and Emanuel Lasker, the same position occurred three times, but no draw was claimed. From the position in the diagram, after 34...h5, the moves were:
The game continued; Lasker blundered and resigned on move 46. Capablanca repeated the position to gain time on the clock .

Alekhine versus Lasker, 1914

The first game between world champion Emanuel Lasker and future world champion Alexander Alekhine ended in a short draw, due to a forced repetition of position: 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nc3 Bb4 6.Nxc6 bxc6 7.Bd3 d5 8.exd5 cxd5 9.0-0 0-0 10.Bg5 Be6 11.Qf3 Be7 12.Rfe1 h6 13.Bxh6 gxh6 14.Rxe6 fxe6 15.Qg3+ Kh8 16.Qg6 and the players agreed to a draw because Black cannot avoid the repetition of position: 16...Qe8 17.Qxh6+ Kg8 18.Qg5+ Kh8 19.Qh6+ .
These two players had another game in 1914 in which Alekhine again achieved a draw by a similar process.

Korchnoi versus Portisch, 1970

A famous draw by threefold repetition occurred in a game between Viktor Korchnoi and Lajos Portisch in 1970 in the Russia vs Rest of the World match. Portisch allowed a threefold repetition in a winning position and was criticized by teammate Bobby Fischer for allowing it. If Portisch had won the game, the match would have been a tie. Play continued:

Kasparov versus Deep Blue, 1997

In the game Garry Kasparov–Deep Blue, 1997 the players agreed to a draw, because if White played 50.g8=Q, Black could get a draw by threefold repetition: 50...Rd1+, 51.K-any, Rd2+ 52.Kb1 Rd1+, etc..

In the opening

Some chess opening lines have been analyzed out to a draw by threefold repetition.
One example is this position from a line of the Pirc Defence. Black can get a draw after the moves 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.f4 Bg7 5.Nf3 c5 6.Bb5+ Bd7 7.e5 Ng4 8.e6 fxe6 9.Ng5 Bxb5! 10.Nxe6 Bxd4! 11.Nxd8 Bf2+ 12.Kd2 Be3+ 13.Ke1 Bf2+ and White cannot escape the checks.

Repeating a position to gain time

Players sometimes repeat a position once not in order to draw, but to gain time on the clock or to bring themselves closer to the time control. Occasionally, players miscount and inadvertently repeat the position more than once, thus allowing their opponent to claim a draw in an unfavourable position. The game Ponomariov–Adams, Wijk aan Zee 2005 may have been an example of this.

Incorrect claims

Even top players have made [|incorrect claims] of a draw under this rule. The Karpov–Miles game is an example of the right to castle having to be the same in all positions. The Fischer–Spassky game is an example that it must be the same player's move in all three positions.

Karpov versus Miles

The clause about the right to en passant and the right to castle is a subtle but important one. In a game between grandmasters Anatoly Karpov and Tony Miles, Karpov had less than five minutes remaining on his clock in which to finish a specified number of moves or forfeit the game. He claimed a draw by repetition after checking his scoresheet carefully, whereupon it was pointed out to him that in the first occurrence of position, Black'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 taken the draw. See the diagram for the position after 22. Nb5. The game continued 22... Ra4 23. Nc3 Ra8 24. Nb5 Ra4 25. Nc3 Ra8 26. Nb5. Black could castle the first time the position in the diagram occurred, but not when the position was repeated.

Fischer versus Spassky

In the twentieth game of the 1972 World Chess Championship between Bobby Fischer and Boris Spassky, Fischer called the Lothar Schmid to claim a draw because of threefold repetition. Spassky did not dispute it and signed the scoresheets before the arbiter ruled. After the draw had been agreed, it was pointed out that the position had occurred after White's forty-eighth and fiftieth moves, and again after Black's fifty-fourth move. So the claim was actually invalid because it was not the same player's turn to move in all three instances, but the draw result stood.

History of the rule

At various times in the history of chess, the rule has been variously formulated. In Tim Harding's MegaCorr database, 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 7.0-0 0-0 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.
The first use of such a rule was in a tournament in London in 1883, but was stated vaguely: "... if a series of moves be repeated three times the opponent can claim a draw." The rules for the first official World Chess Championship 1886 match between Wilhelm Steinitz and Johannes Zukertort stated: "... if both players repeat the same series of moves six times in succession, then either player may claim a draw." In two of the games the same position was repeated three times. The rule was modified soon afterward to be based on positions instead of moves, and for three repetitions. Draws by this method used to be uncommon.
The first edition of the FIDE rule from 1928 already defines the threefold repetition rule without considering castling and en passant capture rights. To additionally consider castling and en passant capture rights was implicitly introduced in 1975 and explicitly worded in 1985. Prior to that, a 1964 FIDE interpretation established the same.
The fivefold repetition rule was implemented in July 2014.

Pillsbury versus Burn

In this 1898 Vienna tournament game between Harry Pillsbury and Amos Burn, the same position occurred three times, but no draw could be claimed under the rules at the time. The tournament was played under the rules of Bilguer's Handbuch des Schachspiels, in which the three-fold rule was stated as the repetition of moves or a sequence of moves, not a position. In the diagramed position, the game continued 43.Qb2 Kh6 44.Qc2 Kh7 45.Qb2 Kg8 46.Qc2 Kg7 47.Qb2 Kh7 48.Qc2 Kh6 49.Qb2 Kh7 50.Qc2 Kg7 51.Qb2. Under modern rules, Black could claim a draw by informing the arbiter of their intention to play 50...Kg7, producing the same position as had occurred after 42...Qe3 and 46...Kg7. Alternatively, after 51.Qb2, Black could claim a draw immediately because White has repeated the position after 43.Qb2 and 47.Qb2. Burn went on to win the game.

Other games

In many abstract strategy games there are rules to cover repetition of position. In some games this results in a draw, in others it is forbidden to repeat a position.
Currently, shogi employs a fourfold repetition rule, which is required to end in a draw. Each player must have the same pieces in hand as well as the same position on the board. The result is a draw. However, a fourfold repetition with perpetual checks is illegal, and results not in a draw but in a loss by the checking player.
In Xiangqi, rules about repetitions vary between different sets of rules, but generally perpetual attacks, including perpetual check, perpetual threatmate, and perpetual chase, are forbidden.
Arimaa does not allow threefold repetition of the same position with the same player to move.
In Go, a player may not make a move which repeats a previous position, as would occur if a player were to immediately recapture a stone in a ko situation. Creating ko threats is an important strategic consideration in Go.