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| Ashot Uzunyan, Best Problems, 10/2013. Código FEN: 6nr/R4ppk/3P3n/3KpP1N/4BNPR/5PpP/6p1/8 w - e6 0 1. |
As Brancas jogam e dão xeque-mate em 2 lances!
(White to play and give checkmate in 2 moves!)
PCFilho
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quinta-feira, 4 de abril de 2019
Xadrez - Mate em 2! (Ashot Uzunyan)
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ResponderExcluirThe black knight at g8 is poised to deliver check at either e7 or f6 if White allows it. The try 1 Rxf7? (threat 2 Rxg7) answers 1 ... Sf6+ with the pin-mate 2 Sxf6, but 1 ... Se7+! still refutes. So, it seems that White needs to deliver check himself. However, 1 f6+? doesn't cut it, as 1 ... Sf5! refutes this try. This seemingly leaves no solution. The solution lies in using retrograde analysis to find out what Black's last move could have been. We eliminate the following units from consideration for the following reasons:
ResponderExcluirKing: The only empty square next to it is g6, and on that square it would be in check from a pawn and a knight simultaneously, which is impossible.
Rook, h6-knight, g6-pawn, g5-pawn: Every square that any of these units could have moved from is occupied.
g8-knight: It could only have moved from e7 or f6, and on either of those squares it has White in check after White has moved, which is an illegal situtation.
f7-pawn, g7-pawn: Each of these pawns is still on its starting square.
So the unit that moved last is the pawn that is currently on e5. It could not have moved from e6, as from there it has White in check after White has moved, which is illegal. It couldn't have made a capture from f6 either, for if it had, then it had to have made another capture on an earlier move, and these captures, together with the captures the black pawns currently on g3 and g2 would have needed to make in order to get to those squares, add up to more captures than are accounted for by the missing white units (only seven white units are missing and nine captures in all would have been required). Therefore, Black's last move must have been ... e7-e5, and therefore the key 1 fxe6ep+! is legal. The post-key play is as follows: 1 ... Sf5 2 Sf6; 1 ... g6 2 Bxg6; 1 ... f5 2 Rxg7.
Well done, Jake.
ExcluirAs usual, very instructive explanation. Thank you for that.