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Chessville
Chess
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Perpetual Check Perpetual check is a defensive technique that can help save an otherwise lost position. Perpetual check has either of two possible aims, both resulting in a drawn game: three-time repetition of the position, or 50 consecutive moves without a pawn move or a capture. This latter type occurs only in the event of such endings as king & queen vs king & queen, or king & rook vs king & rook, where one side can keep checking the opponent's king, but not actually make any progress towards winning, and we will not address those in this article. Learn more about these basic draws here. The idea of perpetual check is to force your opponent to repeat the position. Sometimes he will have no choice but to repeat the position, while other times the alternative may be worse than the draw by repetition. Here's a very simplified position to illustrate the idea of
perpetual check:
White is in check, and has only one possible move - 1.Kh1,
after which Black can play 1...Qf3+
And once again, White has only one move, 2.Kg1. Black then repeats the original position a second time with 2...Qg4+. If they continued the game this way, the game would end as a draw by repetition the third time the position is repeated. Of course, proper chess etiquette would be for White to offer Black a draw rather than play things out to the end. Here's another example, this time with a little more
material on the board:
White is down a rook, and faces near certain doom, or would
were it not for 1.Qe8+! Black has only one response, 1...Kh7.
Now White forces the Black king back to it's previous square with 2.Qh5+, leaving Black only one possible response, 2...Kg8. This is our starting position again! Draw. Another example, this time without queens:
White is about to queen the b-pawn, and Black can prevent
the promotion only through use of the perpetual check, starting with
1...Ng4+. White only has one legal response, 2.Kh1.
Next Black plays 2...Nf2+, and once again White only
has one legal move - 3.Kh2.
Can you guess Black's next move? 4...Ng4+ repeats the position. There is nothing White can do to stop the three-fold repetition, so White should be gracious and offer the draw. The possibility of perpetual check is something that you
should always be on the lookout for, whether you're winning or losing.
Here's an example where one player was alert to the possibility and saved a
lost game, while the second player was oblivious to the idea, and watched a
hard-fought win turn abruptly into a draw.
Black's battery on the a8-h1 diagonal is very powerful, and he should play 1...Qd5 with a winning position. Instead, he miscalculates, and plays 1...Bxd4 instead, thinking that White can't play 2.Qxd4?? because of 2...Qxg2 mate. White, however, sees a defensive possibility based on perpetual check. Do you see it? White moves 2.Qxf7+ Kh8
Now White combines a pair of tactical themes (weak back rank
and deflection) to create the conditions for perpetual check. First,
White deflects the Black queen from guarding the f6 square with 3.Be4!
Qxe4. If 3...Rxe4?? 4.Qf8 mate (weak back rank).
Now White gets rid of the other guardian of f6, Black's
bishop at d4: 4.Bf6+ Bxf6 5.Qxf6+ Kg8 6.Qf7+ Kh8 7.Qf6+
Black can not stop the White checks, as the queen shuttles back and forth from f6 to f7 and back again. When your position is lost anyway, you don't have to worry
about throwing more material at your opponent in order to salvage a draw, so
when you are ahead, watch out for sacrificial continuations by your
opponent! Sometimes the player has a choice to avoid perpetual check,
but only at the cost of losing the game. Here's an example of both
situations:
1.fxg6 Nc3+ 2.Qxc3 White happily gives up her royal
highness in order to save His Royal Highness. 2.bxc3 bxc3+ 3.Ka1 cxd2 4.Nf5+ leads to the same idea as occurs in the main line. 2...bxc3
3.Nf5+
3...Kg8 Not 3...Kh8?? 4.g7+ Kg8 5.Nh6 mate. 4.Ne7+ Kg7 Once again 4...Kh8?? fails to 5.g7 mate. 5.Nf5+ and we have now repeated the position after 3.Nf5+. Black can only choose between getting mated and accepting a draw by perpetual check. One more example, offered by Chessville's Forum Host, Kelly
Atkins, and it is based on the game Wolf-Tarrasch 1923. This one's a
bit more complicated, and the variations may be hard to follow without a
board, so
click here for a javascript board to follow along on.
White is not only a piece down, but Black's bishop at c5 has skewered his two rooks; he's about to lose the exchange, leaving him a full rook down. There is a saving tactic though - White salvages a draw from this otherwise completely lost position by forcing a perpetual check, beginning with 23.Rxg7+. Black must recapture, or face a forced mate: 23...Kxg7 (23...Kh8 24.Rxh7+ Bxh7 [24...Kg8 25.Rh8+ Kg7 26.Qh6 mate] 25.Qf6+ Kg8 26.Rg2+ Bg6 27.Qxg6+ Black's f7 pawn is pinned by the White bishop at b3. 27...Kh8 28.Qg7 mate) 24.Qf6+ Kg8 25.Rg2+ Bg6 26.Rxg6+ hxg6 The f7 pawn is pinned by White's bishop at b3. 27.Qxg6+ Black can do nothing but shuffle his king back and forth from g8 to h8 while White's queen administers a perpetual check. 27...Kh8 28.Qh6+ Kg8 29.Qg6+ ½-½ Feeling confident now? Do you understand the concept? Try your hand at these practice exercises: Exercise 1 Exercise 2 Exercise 3
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