Légal's Mate

Légal's mate is a famous trap where White sacrifices the queen to a bishop, then mates with a knight and a bishop. The knight on d5 gives check, and the bishop on f7 protects the knight's square, so the king cannot escape.

The finished shape

This is the finished shape. Légal's mate is a famous trap where White sacrifices the queen to a bishop, then mates with a knight and a bishop.

FEN: r2q1bnr/ppp1kBpp/2np4/3NN3/4P3/7P/PPPP1PP1/R1BbK2R b KQ - 2 8

a b c d e f g h
8 r . . q . b n r 8
7 p p p . k B p p 7
6 . . n p . . . . 6
5 . . . N N . . . 5
4 . . . . P . . . 4
3 . . . . . . . P 3
2 P P P P . P P . 2
1 R . B b K . . R 1
  a b c d e f g h

The worked example

Here is the mating move. The knight on d5 gives check, and the bishop on f7 protects the knight's square, so the king cannot escape.

FEN: r2q1bnr/ppp1kBpp/2np4/4N3/4P3/2N4P/PPPP1PP1/R1BbK2R w KQ - 1 8

a b c d e f g h
8 r . . q . b n r 8
7 p p p . k B p p 7
6 . . n p . . . . 6
5 . . . . N . . . 5
4 . . . . P . . . 4
3 . . N . . . . P 3
2 P P P P . P P . 2
1 R . B b K . . R 1
  a b c d e f g h

How to prevent it

The defender plays Nxe5 instead, and the trap no longer works.

FEN: r2qkbnr/ppp2ppp/2np4/4N2b/2B1P3/2N4P/PPPP1PP1/R1BQK2R b KQkq - 0 6

a b c d e f g h
8 r . . q k b n r 8
7 p p p . . p p p 7
6 . . n p . . . . 6
5 . . . . N . . b 5
4 . . B . P . . . 4
3 . . N . . . . P 3
2 P P P P . P P . 2
1 R . B Q K . . R 1
  a b c d e f g h

Key points

The knight on d5 gives check, and the bishop on f7 protects the knight's square, so the king cannot escape.
The worked example ends with Nd5.
To prevent it, do not take the queen when the knight and bishop are ready to mate.
Black or White plays Nxe5 in the prevention position, and the trap no longer works.
Check every escape square before you play the mating move, because one open square breaks the mate.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Rust Playground

Exercise

Find the checkmate in this position.

Be8 Bg6 Nd5# Bxg8