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Perpetual checkIn the game of chess, perpetual check is a situation in which one player can play an unending series of checks, from which the defending player cannot escape. This typically arises when the player who is checking feels their position in the game is inferior, they cannot deliver checkmate, and wish to force a draw. A draw by perpetual check is no longer one of the rules of chess, but will eventually allow a draw claim by either threefold repetition or the fifty-move rule. Players usually agree to a draw long before that.[1] Perpetual check can also occur in other forms of chess, although the rules relating to it might be different. For example, giving perpetual check is not allowed in shogi and xiangqi, where doing so leads to an automatic loss for the giver. ExamplesExample from Reinfeld
White to move draws by perpetual check, starting with 1.Qe8+.
In this diagram, Black is ahead a rook, a bishop, and a pawn, which would normally be a decisive material advantage. But White, to move, can draw by perpetual check:
The same position will soon repeat for the third time and White can claim a draw by threefold repetition; or the players will agree to a draw. Unzicker versus AverbakhUnzicker vs. Averbakh, 1952
Perpetual check extricates Black from his difficulties.
In the diagram, from Wolfgang Unzicker–Yuri Averbakh, Stockholm Interzonal 1952,[3] Black (on move) would soon be forced to give up one of his rooks for White's c-pawn (to prevent it from promoting or to capture the promoted queen after promotion). He can, however, exploit the weakness of White's kingside pawn structure with
Threatening 29...Qh2#. If 29.hxg4 then 29...Qf2+, salvaging a draw by threefold repetition with checks by moving the queen alternatively to f2 and h4. Hamppe versus MeitnerHamppe vs. Meitner, 1872
Down massive amounts of material, Black forces a draw by perpetual check.
In a classic game Carl Hamppe–Philipp Meitner, Vienna 1872,[4] following a series of sacrifices Black forced the game to the position in the diagram, where he drew by a perpetual check:
If 17.Kxb7?? Kd7 18.Qg4+ Kd6 followed by ...Rhb8#.
If 18.Ka4?, 18...Bc4 and 19...b5#.
Leko versus KramnikLeko vs. Kramnik, 2008
Position after 24.Qxf5
In the game Peter Leko–Vladimir Kramnik, Corus 2008, Black was able to obtain a draw because of perpetual check:[5]
If 28.Kd2? Rd8+ 29.Ke2 Qe7+. Fischer versus Tal
A perpetual check saved a draw for Mikhail Tal in the game Bobby Fischer–Tal, Leipzig 1960,[6] played in the 14th Chess Olympiad, while Tal was World Champion. In this position Black played
and the game was drawn.[7] (After 22.Kh1, then 22...Qf3+ 23.Kg1 Qg4+ forces perpetual check.) Mutual perpetual check
Mutual discovered perpetual check with nightriders
A mutual perpetual check is not possible using only the orthodox chess pieces, but it is possible using some fairy chess pieces. In the diagram to the right, the pieces represented as upside-down knights are nightriders: they move any number of knight-moves in a given direction until they are blocked by something along the path (that is, a nightrider is to a knight as a queen is to a king, ignoring the rules on check). There could follow:
and so on. This is in fact a mutual perpetual discovered check.[9] Noam Elkies, 1999
Mutual discovered perpetual check with a camel
Noam Elkies devised a mutual discovered perpetual check position that requires only one fairy piece in 1999. The piece represented by an inverted knight here is a camel, a (1,3)-leaper. There could follow:
and so on.[10] Perpetual pursuitS. Birnov, 1928
White to play and draw
Related to perpetual check is the perpetual pursuit, which differs in that the continually attacked piece is not the king. The result is similar, in that the opposing side's attack stalls because of the need to respond to the continuous threats.[11] In the study to the right, White's situation seems hopeless: they are down a piece and cannot stop Black's h-pawn, and their passed a-pawn can easily be stopped by Black's bishop. However, they can save themself by restricting the bishop's movement to set up a perpetual pursuit. They begin:
A direct pawn race with 1...h3? fails, as White promotes first and covers the promotion square.
This pawn sacrifice forces Black to limit their bishop's scope along the long diagonal.
Forced, as Black has to play ...Bd5 to stop the pawn.
Denying another square to the bishop, which must stay on the a8–h1 diagonal. This forces
And White can then begin the perpetual pursuit:
Black can make no progress.
An example of perpetual pursuit being used in a game occurred in István Bilek–Harry Schüssler, Poutiainen Memorial 1978. Bilek thought he could win the enemy queen with the combination
However, Schüssler replied
and Bilek conceded the draw. His queen is now trapped, and with ...Bb4+ threatening to win it, he has nothing better than 13.0-0 Bg7 14.Qd6 Bf8 15.Qd8 Bg7 with another perpetual pursuit. HistoryN.N. vs. Unknown, 1750
Final position after 15...Kh7
The Oxford Encyclopedia of Chess Games, Volume 1 (1485–1866) includes all recorded games played up to 1800.[12] The earliest example of perpetual check contained in it is a game played by two unknown players in 1750:
The next examples of perpetual check in the book are two games, both ending in perpetual check, played in 1788 between Bowdler and Philidor, with Philidor giving odds of pawn and move.[14] A draw by perpetual check used to be in the rules of chess.[15][16] Howard Staunton gave it as one of six ways to draw a game in The Chess-Player's Handbook.[17] It has since been removed because perpetual check will eventually allow a draw claim by either threefold repetition or the fifty-move rule. If a player demonstrates intent to perform perpetual check, the players usually agree to a draw.[18] See alsoReferences
Bibliography
External links
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