In the game of chess, perpetual check is a situation in which one player can force a draw by an unending series of checks. This typically arises when the player who is checking cannot deliver checkmate, and failing to continue the series of checks gives the opponent at least a chance to win. A draw by perpetual check is no longer one of the rules of chess; however, such a situation will eventually allow a draw claim by either threefold repetition or the fifty-move rule. Players usually agree to a draw long before that, however.[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.

Examples

Example from Reinfeld
abcdefgh
8
g8 black king
g7 black pawn
g5 white king
h5 white queen
b4 black rook
a3 black queen
d3 black bishop
8
77
66
55
44
33
22
11
abcdefgh
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:

1. Qe8+ Kh7
2. Qh5+ Kg8
3. Qe8+ etc.[2]

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 Averbakh

Unzicker vs. Averbakh, 1952
abcdefgh
8
f8 black rook
g8 black king
b7 black rook
c7 white pawn
g7 black pawn
h7 black pawn
a6 black pawn
f6 black knight
d5 white pawn
e5 black pawn
b4 white pawn
e4 white pawn
f4 black queen
c3 white queen
h3 white pawn
a2 white pawn
g2 white pawn
a1 white rook
e1 white rook
g1 white king
8
77
66
55
44
33
22
11
abcdefgh
Perpetual check extricates Black from his difficulties.

In the diagram, from Wolfgang UnzickerYuri 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

27... Rxc7!
28. Qxc7 Ng4!

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 Meitner

Hamppe vs. Meitner, 1872
abcdefgh
8
a8 black rook
c8 black bishop
d8 black king
h8 black rook
c7 black pawn
f7 black pawn
g7 black pawn
h7 black pawn
b6 black pawn
c6 white king
a5 black pawn
d5 black pawn
e5 black pawn
a3 white pawn
b2 white pawn
c2 white pawn
d2 white pawn
g2 white pawn
h2 white pawn
a1 white rook
c1 white bishop
d1 white queen
g1 white knight
h1 white rook
8
77
66
55
44
33
22
11
abcdefgh
Down massive amounts of material, Black forces a draw by perpetual check.

In a classic game Carl HamppePhilipp 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:

16... Bb7+!
17. Kb5

If 17.Kxb7?? Kd7 18.Qg4+ Kd6 followed by ...Rhb8#.

17... Ba6+
18. Kc6

If 18.Ka4?, 18...Bc4 and 19...b5#.

18... Bb7+ ½–½

Leko versus Kramnik

Leko vs. Kramnik, 2008
abcdefgh
8
a8 black rook
h8 black king
a7 black pawn
b7 black pawn
g7 black pawn
h7 black pawn
c6 black pawn
f5 white queen
h4 white pawn
c3 black queen
c2 white pawn
f2 white pawn
g2 white pawn
b1 white king
d1 white rook
h1 white rook
8
77
66
55
44
33
22
11
abcdefgh
Position after 24.Qxf5

In the game Peter LekoVladimir Kramnik, Corus 2008, Black was able to obtain a draw because of perpetual check:[5]

24... Qb4+
25. Ka2 Qa4+
26. Kb2 Qb4+
27. Kc1 Qa3+
28. Kb1 ½–½

If 28.Kd2? Rd8+ 29.Ke2 Qe7+.

Fischer versus Tal

Fischer vs. Tal, 1960
abcdefgh
8
c8 black king
a7 black pawn
b7 black pawn
e7 black knight
h7 white queen
e6 black queen
a5 white pawn
d5 black pawn
a3 white pawn
c3 black pawn
c2 white pawn
f2 white pawn
g2 white king
h2 white pawn
f1 white rook
8
77
66
55
44
33
22
11
abcdefgh
Position after 21.Kxg2

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

 21... Qg4+

and the game was drawn.[7] (After 22.Kh1, then 22...Qf3+ 23.Kg1 Qg4+ forces perpetual check.)

Mutual perpetual check

abcdefgh
8
d6 black rook
e6 black rook
e5 black king
d3 white king
c1 white upside-down knight
f1 white upside-down knight
8
77
66
55
44
33
22
11
abcdefgh
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:

1. Ke3+ Kd5+
2. Kd3+ Ke5+
3. Ke3+ Kd5+

and so on. This is in fact a mutual perpetual discovered check.[9]

Noam Elkies, 1999
abcdefgh
8
b6 black king
a5 black rook
e5 white king
d4 white knight
b2 black upside-down knight
a1 black bishop
b1 white rook
g1 white bishop
8
77
66
55
44
33
22
11
abcdefgh
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:

1. Nb5+ Cc5+
2. Nd4+ Cb2+
3. Nb5+ Cc5+

and so on.[10]

Perpetual pursuit

S. Birnov, 1928
abcdefgh
8
g8 black bishop
c7 white king
a5 white pawn
c5 black pawn
f5 black king
c4 white pawn
h4 black pawn
c3 white pawn
e3 white pawn
8
77
66
55
44
33
22
11
abcdefgh
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: he is down a piece and cannot stop Black's h-pawn, and his passed a-pawn can easily be stopped by Black's bishop. However, he can save himself by restricting the bishop's movement to set up a perpetual pursuit. He begins:

1. a6 Bxc4

A direct pawn race with 1...h3? fails, as White promotes first and covers the promotion square.

2. e4+!

This pawn sacrifice forces Black to limit his bishop's scope along the long diagonal.

2... Kxe4

Forced, as Black has to play ...Bd5 to stop the pawn.

3. a7 Bd5
4. c4!

Denying another square to the bishop, which must stay on the a8–h1 diagonal. This forces

4... Ba8

And White can then begin the perpetual pursuit:

5. Kb8 Bc6
6. Kc7 Ba8

Black can make no progress.

Bilek vs. Schüssler, 1978
abcdefgh
8
a8 black rook
b8 black knight
d8 black queen
e8 black king
f8 black bishop
h8 black rook
a7 black pawn
e7 black knight
f7 black pawn
g7 black pawn
h7 black pawn
b6 black pawn
c6 black pawn
d5 white knight
c4 white bishop
f3 white pawn
g3 white pawn
a2 white pawn
b2 white pawn
f2 white pawn
h2 white pawn
a1 white rook
c1 white bishop
d1 white queen
e1 white king
h1 white rook
8
77
66
55
44
33
22
11
abcdefgh
White attempts to win the enemy queen...
abcdefgh
8
a8 black rook
b8 black knight
d8 white queen
f8 black bishop
h8 black rook
a7 black pawn
f7 black king
h7 black pawn
b6 black pawn
c6 black pawn
f6 black pawn
d5 black knight
f3 white pawn
g3 white pawn
a2 white pawn
b2 white pawn
f2 white pawn
h2 white pawn
a1 white rook
c1 white bishop
e1 white king
h1 white rook
8
77
66
55
44
33
22
11
abcdefgh
...but traps his own into a perpetual pursuit.

An example of perpetual pursuit being used in a game occurred in István BilekHarry Schüssler, Poutiainen Memorial 1978. Bilek thought he could win the enemy queen with the combination

10. Nf6+ gxf6
11. Bxf7+ Kxf7
12. Qxd8

However, Schüssler replied

12... Nd5! ½–½

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.

History

N.N. vs. Unknown, 1750
abcdefgh
8
a8 black rook
c8 black bishop
a7 black pawn
b7 black pawn
c7 black pawn
f7 white bishop
g7 black pawn
h7 black king
d6 black pawn
g6 white knight
h6 black pawn
e5 black pawn
e4 white pawn
h4 black queen
d3 white pawn
f3 black knight
h3 white pawn
a2 white pawn
b2 white pawn
c2 white pawn
f2 black bishop
g2 white pawn
a1 white rook
c1 white bishop
h1 white king
8
77
66
55
44
33
22
11
abcdefgh
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:

N.N. versus Unknown, 1750
1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. 0-0 (the rules of castling not yet having been standardized in their current form, White moved his king to h1 and his rook to f1) 4... Nf6 5. Nc3 Ng4 6. d3 0-0 (Black moved his king to h8 and his rook to f8) 7. Ng5 d6 8. h3 h6 9. Nxf7+ Rxf7 10. Bxf7 Qh4 11. Qf3 Nxf2+ 12. Rxf2 Bxf2 13. Nd5 Nd4 14. Ne7 Nxf3 15. Ng6+ Kh7 ½–½ in light of 16.Nf8+ Kh8 17.Ng6+ etc.[13]

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 also

References

  1. (Burgess 2000:478)
  2. (Reinfeld 1958:42–43)
  3. "Unzicker vs. Averbakh, Stockholm 1952". Chessgames.com.
  4. "Hamppe vs. Meitner, Vienna 1872". Chessgames.com.
  5. "Leko vs. Kramnik, Wijk aan Zee 2008". Chessgames.com.
  6. "Fischer vs. Tal, Leipzig 1960". Chessgames.com.
  7. (Evans 1970:53)
  8. Die Schwalbe
  9. Tim Krabbé, Open chess diary see item 120
  10. Tim Krabbé, Open chess diary see item 125
  11. Seirawan, Yasser; Silman, Jeremy (2003). Winning Chess Tactics. London: Everyman Chess. pp. 119–121. ISBN 1857443330.
  12. (Levy & O'Connell 1981:ix)
  13. (Levy & O'Connell 1981:9)
  14. (Levy & O'Connell 1981:12)
  15. (Reinfeld 1954:175)
  16. (Reinfeld 1958:41–43)
  17. (Staunton 1847:21)
  18. (Hooper & Whyld 1992)

Bibliography

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