The key of this exceptionally fine and difficult problem is (1) Kt-d6, forcing Bxd6. The idea of this sacrifice is to change the line of defense of the black Bishop from the diagonal h4-d8 to the diagonal h2-b8, so that he is compelled to defend the threat Q-e2, etc., indicated above by moving to f4, that is to a square on which he can be taken. After (2) Q-e2, B-f4; (3) Pxf4 the stalemate is relieved and Black can take the Pawn d4. But a most surprising mate is now possible, which could not possibly have been foreseen in the original position, namely: (4) Q-e5.
Problems in which no definite number of moves are stipulated for the mate are usually called STUDIES or ENDINGS. They are nothing but game positions in which a maneuver forces the win that is so well hidden that it would probably not be found by a player in an actual game. The following two positions are examples of this class of compositions.
The first move is evident. White must play (1) P-c7, as otherwise Black retreats with the Rook in the d-file and occupies the c- file so that he can be sacrificed at any time for White's dangerous Pawn.
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8 | | | | | | | | |
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7 | | | | | | | | |
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6 | | ^K | ^P | | | | | |
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5 | | | | #R | | | | |
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4 | | | | | | | | |
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3 | | | | | | | | |
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2 | | | | | | | | |
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1 | #K | | | | | | | |
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a b c d e f g h
DIAGRAM 82.—WHITE TO PLAY AND WIN.
After (1) …, R-d6+ White can neither go to b7 on account of R- d7 nor can he play K-c6 or c5 on account of R-d1 followed by R-c1 whereby Black would draw. The only way to win is: (2) K-b5, R- d5+; (3) K-b4, R-d4+; (4) K-b3, R-d3+; (5) K-c2. At last White has succeeded in guarding his rear, and it seems as if Black could not any longer prevent the Pawn from Queening. However, Black plays (5) …, R-d4 and if White queens the Pawn he gives check on C4 forcing Qxc4 which would stalemate the King.
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8 | | | | | | | ^K | |
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7 | | | | | | | ^P | |
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6 | | | #B | ^B | | | | |
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5 | | | | | | | | |
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4 | | | | | | | | |
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3 | | | | | | | | |
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2 | | | ^Kt| | | #P | | #P |
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1 | | | | #K | | | | |
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a b c d e f g h
DIAGRAM 83.—White to Move and Draw.
This is the point where the problem-trick enters the game. White does not promote the Pawn to a Queen but to a Rook, avoiding the stalemate and threatening mate on a8. Black's only defense is R- a4 and now White wins by (7) K-b3 attacking the Rook and threatening mate on c1 at the same time.
In the position of Diagram 83 Black threatens to queen either of his Pawns. White can play (1) Kt-e3+ K-e2; (2) Bxh2, but after Kxe3 there seems to be no way of stopping the Pawn f2.