Two Bishops vs Knight: the Kling and Horwitz Position
White to play and win, after Kling and Horwitz, 1851
PlayTwo bishops beat a lone knight almost every time, and this is the position where that word almost matters. Kling and Horwitz published it in 1851 as a draw. That verdict survived until computer analysis overturned it in 1983.
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Kling and Horwitz: Two Bishops Against a Knight
White to play and win · Win against perfect defense
Waking the engine…
The theory
Two bishops beat a lone knight in nearly every position. This position is the exception that took chess 132 years to settle.
A draw for 132 years. Kling and Horwitz gave this position in 1851 and assessed it as drawn. The knight on b7 sits right next to its king, covering the squares the bishop pair needs, and no human analysis could crack it. Only in 1983 did computer analysis show that White wins.
Why it is so hard. The defense is not one fortress, it is a family of them. Even after you break the setup in this corner, Black tries to reassemble the same king-and-knight formation in another. The winning method has to destroy the b7 construction without letting it be restored anywhere else on the board.
The fifty-move problem. The tablebase gives mate in 57 moves, which is past the fifty-move limit. What rescues the win is that the knight falls first: the capture zeroes the counter, and what is left is the standard two-bishop mate, which does work in any corner.
In this drill the defender holds the fortress without cracking and will not hand you the knight. Take away its squares with the bishop pair, walk your king in to remove the flight squares, and be patient. This is the hardest two-bishop win there is.