Knight and Pawn vs Bishop: The Short Diagonal Loses
White to play and win
PlayOne file changes the verdict. With the pawn on the c-file, the bishop's stopping diagonal is a square shorter, only four squares long. Now the king and knight together can screen the whole of it, and the pawn goes through.
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When the Bishop's Diagonal Is Too Short
White to play and win · Win against perfect defense
Waking the engine…
The theory
A lone bishop can sometimes stop a passed pawn with no help from its king, but only if its stopping diagonal is long enough. The rule is arithmetic: king and knight together can screen four squares of a diagonal, two each.
Five holds, four falls. A five-square diagonal always leaves one square free, so the bishop draws unaided. Shift the pawn one file toward the edge and the diagonal loses a square. Now four squares can be fully screened, and the defending bishop is driven off or blocked.
Two ways through. Promote the pawn either by driving the bishop off its diagonal or by interposing the knight to break its line of sight. Escort with the king, and on the short diagonal one of the two always succeeds.
In this drill the defender will shuffle the bishop to keep the pawn stopped. Cut the diagonal with king and knight, and push the pawn home.
Keep going
The Rook Pawn: A Draw in the Corner
White to play and draw
The Knight Blockade vs Bishop and Pawn
Black to play and draw
The Bishop's Long Diagonal vs Knight and Pawn
Black to play and draw
All 15 bishop vs knight positionsFollow the full curriculum (free)