Légal's Mate: The Trap and How It Works

How the trap works

Black's 3...Bg4 pins the knight on f3 to the queen on d1. White ignores the pin with 5.Nxe5, offering the queen. If Black takes it, 6.Bxf7+ forces the king to e7, and 7.Nd5 is checkmate. The knight on d5 gives check and covers f6. The bishop on f7 covers e8 and e6 and is protected by the knight on e5, which also covers d7. Black's own queen, bishop, and pawn block d8, f8, and d6.

The trap is named after the French player Sire de Légal, who lived in the 18th century.

Why the natural move fails and what to play instead

Taking the queen looks natural because winning a queen for a bishop is usually decisive. Here it costs the game, because White's three minor pieces are already aimed at Black's king. Black should play 5...dxe5. White wins a pawn with 6.Qxg4 and is clearly better, but Black is still in the game.

The trap also depends on Black's earlier choices. With 4...g6, Black spent a move on the kingside instead of guarding e5 or developing a knight, which is why Nxe5 works at all.

The general lesson

A pin to the queen is not absolute. The pinned piece can still move if the resulting position is better than the queen. Before grabbing a queen, look at every check the opponent has afterward.

Common questions