Légal Trap


The Légal Trap or Blackburne Trap is a chess opening, characterized by a queen sacrifice followed by checkmate with minor pieces if Black accepts the sacrifice. The trap is named after the French player Sire de Légal. Joseph Henry Blackburne, a British master and one of the world's top five players in the latter part of the 19th century, set the trap on many occasions.

Natural move sequence

There is a number of ways the trap can arise; the one below shows a natural move sequence from a simultaneous exhibition in Paris. André Cheron, one of France's leading players, won with the trap as White against Jeanlose:
1. e4 e5 2. Nf3 Nc6 3. Bc4 d6
4. Nc3 Bg4
5. h3
5... Bh5
6. Nxe5
6... Bxd1 7. Bxf7+ Ke7 8. Nd5

Légal versus Saint Brie

The original game featured Légal playing at rook odds against Saint Brie in Paris 1750:
1. e4 e5 2. Nf3 d6 3. Bc4 Bg4?! 4. Nc3 g6? 5. Nxe5 Bxd1?? 6. Bxf7+ Ke7 7. Nd5#
1. e4 e5 2. Bc4 d6 3. Nf3 Nc6 4. Nc3 Bg4 5. Nxe5? Bxd1?? 6. Bxf7+ Ke7 7. Nd5# 1–0

Other variations

Considerations

This kind of mate, where an apparently pinned knight moves anyway, allowing capture of the queen, but leading to a checkmate with minor pieces, occasionally occurs at lower levels of play, though masters would not normally fall for it. According to Bjerke, the Légal Trap has ensnared countless unwary players. One author writes that "Blackburne sprang it several hundreds of times during his annual tours."
In general, setting up a "trap" by luring a bishop into a queen capture is not strictly necessary. Any game featuring an advanced knight and Bxf7+ followed by mate with minor pieces would be considered a Légal Mate. The mate succeeds because the square of the advanced knight is unguarded, and the enemy king is blocked by several of its own pieces.