In chess, the threefold repetition rule states that a player may claim a draw if the same position occurs three times during the game. The rule is also known as repetition of position and, in the USCF rules, as triple occurrence of position. Two positions are by definition "the same" if pieces of the same type and color occupy the same squares, the same player has the move, the remaining castling rights are the same and the possibility to capture en passant is the same. The repeated positions need not occur in succession.
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. The claim must be made either before making the move which will produce the third repetition, or after the opponent has made a move producing a third repetition. By contrast, the fivefold repetition rule requires the arbiter to intervene and declare the game drawn if the same position occurs five times, needing no claim by the players.
Similar rules exist in other abstract strategy games such as xiangqi and shogi (cf. sennichite) whereas in Go, repetition of the immediately previous board position is completely disallowed in the first place, and in some regional rule sets repetition of any previous board position is disallowed.
Internet chess servers differ in their handling of draw by repetition. For example, Chess.com draws the game automatically upon a position's third occurrence.
Statement of the rule
The relevant rules in the FIDE laws of chess are summarized as:
:The game is a draw if a position occurs (at least) three times during the game. (Intervening moves do not matter.) It must be claimed by the player with the turn to move. The claim is made:
::(a) If the position is about to appear for the third time, the player making the claim first writes their move on their and notifies the that they intend to make this move.
::or
::(b) If the position has just appeared for the third time, the player with the move can claim the draw.
: Positions are considered the same if
: (1) the same player has the move,
: (2) pieces of the same kind and color occupy the same squares, and
: (3) the possible moves of all the pieces are the same.
: Under (3) above, positions are not considered to be the same if:
::(a) in the first position, a pawn could have been captured en passant (by the en passant rule, in the subsequent positions, the pawn cannot be captured en passant anymore), or
::(b) either player has lost a right to castle, i.e. either king or one of the rooks has been moved, in between repetitions of the position.
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 rule applies to positions, not moves.
Perpetual check is no longer specifically mentioned in the rules of chess; such a situation will eventually resolve to a draw either by repetition, fifty-move rule or (most commonly) by agreement.
If the claim for a draw is incorrect, the opponent is awarded an extra two minutes, the written move (if legal) must be played and the game continues.
Examples
1972 World Championship
The seventeenth and eighteenth game of the 1972 World Championship match in Reykjavik between Bobby Fischer and Boris Spassky were declared draws because of threefold repetition. The twentieth game was drawn after an incorrect claim (see incorrect claims below).
Fischer vs. Petrosian, 1971
In the third game of the 1971 Candidates Final Match in Buenos Aires between Bobby Fischer and Tigran Petrosian, Petrosian (with a better position) accidentally allowed the position after 30.Qe2 () to be repeated three times. Play continued:
:30... Qe5
:31. Qh5 Qf6
31...Qxf4 32.Qxf7+ also leads to threefold repetition.
:32. Qe2 (second time) Re5
:33. Qd3 Rd5?
and then Fischer wrote his next move
:34. Qe2 (third time) ½-½
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 vs. 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 in Havana between José Raúl Capablanca and Emanuel Lasker, the same position occurred three times, but no draw was claimed. After 34...h5 (), the moves were:
:35. Qd8+ Kg7
:36. Qg5+ Kf8 (second time)
:37. Qd8+ Kg7
:38. Qg5+ Kf8 (third time)
Capablanca had repeated the moves to gain time on the clock (i.e. get in some quick moves before time control). The game continued without a draw being claimed; Lasker blundered and resigned on move 46. (Capablanca went on to win the match and become world champion.)
Two games between Alekhine and Lasker, 1914
The game between Alexander Alekhine and world champion Emanuel Lasker in Moscow 1914 ended in a short draw. After 16.Qg6 () the players agreed to a draw because Alekhine can force the threefold repetition, for example 16...Qe8 17.Qxh6+ Kg8 18.Qg5+ Kh8 19.Qh6+.
In the first game between the two players in the St. Petersburg tournament 1914, Alekhine, this time with the black pieces, after 21.Qd4 (), forced a draw by threefold repetition using a similar process.
Portisch vs. Korchnoi, 1970
A famous draw for threefold repetition occurred in the fourth