Lesson
White to move. Main line: 1. Nf7#
Nf7# attacks h8 with the knight’s L-shaped move. A knight check cannot be blocked, so Black can only capture the knight or move the king. The white king on f6 protects f7, ruling out a capture.
The rook on g1 controls g8, the bishop on c2 controls h7, and the king on f6 controls g7. Each helper takes exactly one flight square, creating a clean example of four-piece coordination.
When a knight can check a cornered king, list the three adjacent squares rather than searching for an interposition. Knight checks become mates when those squares are occupied or controlled and the knight itself is protected.