17 June 2010

"En passant" chess puzzle

Futility Closet posts some very interesting chess puzzles, and the one above is one of best I have seen.

White plays B-g2+.  Black responds with pawn to d5, which (he says) blocks the check and uncovers a checkmate by the black bishop at c8.   White responds that the black pawn never got to/can't go to d5, because the white pawn takes it "en passant" at d6. 

More at the link (puzzle from Heinrich Fraenkel, Adventure in Chess, 1951.)

11 comments:

  1. Well, answer is simple. Black moves pawn to d5, white takes pawn en passent thus Black can move again. Bishop takes king on h3 and white is now missing a king... Game over, black wins.

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  2. Yeah, I was no expert, but it seemed to me "en passant" or not, in chess only one side is moving at a time, so black could indeed complete his move, then white can make his, taking the pawn. Then it is blacks turn again, not whites.

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  3. From what I remember, en passant is a singular move. I.e. it isn't like a mine being set off as you step on it, as is being shown in that example. The black piece makes their move first, the white piece -then- makes en passant, and then it's black's turn, making it checkmate in their favour.

    A very clever puzzle!

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  4. I don't believe that white would be allowed to make the "en passant" move because he is currently in check as the black bishop is threatening the white king. Even if the "en passant" was allowed it would next be black's turn allowing him to capture the white king with his bishop.

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  5. Ryan, white can't be put into check until black gets out of check, and black can't get out of check except by moving the pawn to d5 - which he can't do, because it can never get there...

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  6. << black can't get out of check except by moving the pawn to d5 >>
    True.

    << which he can't do, because it can never get there >>
    Not true. En passant capture is not automatic (hence James' analogy to a landmine). After ... d5, White is in check and MUST respond to that. An en passant capture would not remove the condition of check (by the bishop on c8) and thus is not allowed. White has no legal move ... Black wins.

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  7. En passant is suppose to exist to allow pawns to quickly advance but not to escape the reach of other pawns. Interposing with a double push shouldn't be allowed if en passant would stop the action. The argument some have offered is that black's capture takes a move, but really black couldn't really interpose because of the capture and thus the first bishop move should properly have been checkmate and the king should have been able to be taken en passant. Not according to the actual rules mind you. The puzzle is largely the letter of the law vs. the spirit of the law.

    If black couldn't have pushed his pawn one space, he shouldn't have been able to push it two spaces. Much like you cannot castle your king through check. En passant when captured is treated like the pawn was only moved one square in which case the first checkmate should stand and the pawn should not be allowed to be interposed. I'm pretty sure the letter of the law is clear and black wins, but white should win by the spirit of the rules, which is to say that double pushing pawns are allowed unless they were captured on the first square on a virtual move, as that's a distinct possibility, the double push shouldn't have been allowed anyhow.

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  8. HIARCS says 1...d5 is mate, which I guess I have to agree with. White never has time to play 2...cxd6 because he is already checkmated. 0-1

    Very interesting puzzle... or whatever you might call that.

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  9. Some of y'all seem to be a little confused. There is no letter of the law/spirit of the law dichotomy or disagreement in chess and certainly not in this puzzle. The rules are the rules. A move in chess actually consists of two half-moves, a move from white and a move from black. Each half-move results in a distinct position unto itself. Maybe some of you are also confused about the en passant rule. Just because the conditions for an e.p. capture are met does not mean the capture must be carried out. As they say, it's not checkers, you don't have to take. Also, no capture happens instantaneously. With the exception of castling, only one piece moves per one half-move at a time.

    Therefore: after 1. Bg2+ black plays ...d5#, both blocking the check and delivering discovered mate. This is how the moves would be written on a tournament score sheet. The black pawn certainly DOES reach the d5 square thereby blocking the check from g2 and opening the bishop upon the white king. If it were not the case that white was checkmated, he would have the option of playing cxd6 e.p. but this does not in anyway change the fact that blacks d-pawn reached the d5 square, albeit for one half-move.

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  10. Did you know that the en passant capture is compulsory when the player is in Zugzwang, and no other move is available on the board ?

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    Replies
    1. In chess puzzles, is it true that en passant as the first move is illegal,unless it can be proven that the only last move possible was that pawn moving two steps? If this is true, where is it written or where is it stated on any fide rules on chess puzzles.

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