Knight versus Bishop

Failed study by F. Hey, 1913, which is example 272 in Test Your Endgame Ability by August Livshits and Jonathan Speelman (1988) which followed the composer's incorrect claim that White to play could force a win. There are many traps but a defence is possible.

In Averbakh's Comprehensive Chess Endings, volume 2 (example 238, pages 89-90) the correct result is found by a method of corresponding squares.

The composer's task was White to play wins, Black to play draws. The latter is correct (1...Bd6), as in the Speelman book, but the tablebase agrees with Averbakh that Black can also draw when it is White to move. Some of the variations are instructive.

F. Hey, 1913 - Refuted by Averbakh
[Additional lines by T.Harding]

1.Ne6 is the supposed solution in the book. Obviously White wants to play Nf7 mate in two and threatens to do this via either d8 or g5. Black must manoeuvre his B to prevent this. [1.Nc6 also threatens Nd8 with Ne5 as the alternative route if Black covers d8. 1...Bc7[] and both routes are defended. (1...Bh4? 2.Ne5 ) ] 1...Bh4!= Prevents the mates. White can try to combine threats to the a-pawn with mate threats but Black can cope: [1...Bc7 2.Ng5 and mates (NOT 2.Nxc7 stalemate: the "point" of the study.) ] 2.Ng7!? is one way to head for c4, the only other square from which the a-pawn can be threatened. This is not as dangerous because from c4 White is only in contact with e5, not with d8. Black has three possible replies but they require precise follow-up. [2.Nd4 to approach the a-pawn via c6, which is in contact with both d8 and a5. 2...Bg3! This correspondence (Nd4/Bg3) is missing from Averbakh's explanation. 3.Nf3! Tests Black from another direction. From here the knight can reach c4 (via d2), c6 (via d4 or e5) or f7 (via e5 or g5) in two moves. Averbakh says that only one square for the bishop prevents all these tries and so corresponds to f3: (3.Nc6 3 Nb3 transposes to the note to move 3 in the main line. 3...Bc7 This is the same as the 1 Nc6 line.) 3...Bf4! This cuts out d2, e5 and g5, leaving only 4.Nd4 which we have already noted is answered by 4...Bg3 repeating the position.; 2.Nc5 Idea Nb7, so that the N heads for the d8-f7 route while also attacking the a-pawn. 2...Bg3! 3.Nb7 (3.Nb3 Trying from the other direction but there are two replies that hold: 3...Bc7 (3...Be1 ) ) 3...Bc7! ] 2...Bg3 [2...Bg5!? The most amusing, but 1...Be7 or 1...Bg3 would be more practical. 3.Nf5 White ignores the bishop and continues the agenda. (3.Kxg5 Kxg7 4.Kf5 Kxh7 5.Ke5 Kg6 6.Kd5 Kf6 7.Kc5 Ke6 8.Kb5 Kd6 9.Kxa5 Kc7 10.Ka6 Kb8= ) 3...Bf4! Black blocks both routes to c4 (d6 and e3).; 2...Be7 3.Nf5 Bf8! 4.Ne3 Bd6! 5.Nc4 Bc7! (5...Bb4?? 6.Ne5 ) ] 3.Nf5 heading for c4 via d6 or e3 3...Bf4 Black prevents both those moves. 4.Ne7 Now any square on the b8-h2 diagonal (to meet Nc6 by Bc7) is safe, except for 4...Bc7?? when White wins by zugzwang [4...Bg3 draws, for example, if 5.Kh6 attempting the only other winning manoeuvre (Ng6 mate), Black simply plays 5...Bf4+ 6.Kg6 Bg3 repeating the position.] 5.Nc6 Bb6 6.Ne5 1/2-1/2

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