The Legal Trap: Setting the Oldest Trick in the Book
The Legal Trap is over two centuries old and still works today. Here's the mechanism, the refutation, and why understanding it teaches you something important about chess tactics.
The Legal Trap, named after the 18th-century French master Sire de Légal, is the oldest known intentional chess trap. Despite its age, it continues to catch players today because it exploits a fundamental tactical motif: the pin that isn't really a pin.
The Setup
A typical Legal Trap arises from 1.e4 e5 2.Nf3 d6 3.Bc4 Bg4 4.Nc3 g6 5.Nxe5! Black naturally assumes the knight is protected by the bishop on c4, the e5 pawn defends the knight, and the queen on d1 is pinned to the king. So Black takes: 5...Bxd1??
The Combination
6.Bxf7+! Ke7 7.Nd5# — checkmate. The "pinned" queen was never truly pinned because White was willing to sacrifice it for a three-piece mating attack. The trap works because it exploits the assumption that a pin to the queen prevents the piece from moving.
The Lesson
The Legal Trap teaches the most important lesson in pin-related tactics: always check whether the piece creating the pin can be captured. A pin to the queen is only real if capturing the queen loses material. Always verify the assumption before relying on it.