Chess Openings Lab
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Légal's Mate

White unpins the f3 knight with 5.Nxe5 and leaves the queen on d1 hanging. If Black grabs it with 5...Bxd1, three minor pieces deliver mate in two moves around the black king.

Opening
Philidor Defense
Moves
1.e4 e5 2.Nf3 d6 3.Bc4 Bg4 4.Nc3 g6 5.Nxe5 Bxd1 6.Bxf7+ Ke7 7.Nd5#
Set by
White
The mistake
5...Bxd1
Checked
every move legal; result confirmed by Stockfish 17.1

How the trap works

The line starts as a normal Philidor Defense. After 1.e4 e5 2.Nf3 d6 3.Bc4, Black plays 3...Bg4 and pins the f3 knight against the queen on d1. That pin is the bait. It is only a relative pin: the knight shields the queen, not the king, so White is allowed to move it.

4.Nc3 develops and puts a second knight on the road to d5. Black's 4...g6 is slow, and the evaluation jumps to a clear edge for White. Now 5.Nxe5 takes a pawn and leaves the queen on d1 en prise.

  • 5...Bxd1? is the mistake. Black wins the queen and gets mated.
  • 6.Bxf7+ checks the king. The bishop cannot be taken because the knight on e5 guards f7, and d7 is also covered by that knight, so 6...Ke7 is forced.
  • 7.Nd5# is mate. The knight checks from d5 and covers f6. The bishop on f7 covers e8 and e6. The king's other squares, d8, f8 and d6, are filled by Black's own queen, bishop and pawn.

The key idea is that three minor pieces beat a queen when the enemy king is boxed in by its own army. White gives up the queen to win time, and every tempo goes into checks.

The exact moment it goes wrong is 5...Bxd1. Before that, Black was only a pawn down. Taking the knight back with the d-pawn lets the white queen take the bishop on g4 and win a pawn, which leaves Black worse but still playing. Greed turns a bad position into a lost one in two moves.

For White, the lesson is that a pinned piece is often free to move when the pin is against the queen. For Black, the lesson is to count checks before grabbing material: if the opponent gets Bxf7+ with a knight already on e5, the king is in danger.

How Black avoids it

Black should recapture with ...dxe5. White then plays Qxg4 and is a pawn up with the better game, which is bad for Black but far better than getting mated.

Questions

How does the Légal's Mate work?

The bishop on g4 pins the f3 knight only to the queen, not to the king, so White may break the pin. After 5.Nxe5 Bxd1, 6.Bxf7+ drives the king to e7 and 7.Nd5# finishes, with Black's own queen, bishop and d6 pawn blocking the escape squares.

What is the losing move in the Légal's Mate?

Black's mistake is 5...Bxd1. Black should recapture with ...dxe5. White then plays Qxg4 and is a pawn up with the better game, which is bad for Black but far better than getting mated.

Is the Légal's Mate worth playing for?

Yes for White. The evaluations show White already clearly better after 4...g6 and still clearly better after 5.Nxe5 if Black declines the queen, so White risks nothing.

Where it comes from

More opening traps