Légal's mate is lesson 2 of 10 in Brilliant sacrifices 1: classic traps, an opening course suited to players rated around 900 (beginners). Philidor Defence, C41. White gives the queen and mates with three minor pieces. It has 3 interactive exercises: 3 find-the-move puzzles. You play every move on a board and get feedback straight away. The lesson is free.
What this lesson explains
This is the Philidor Defence. Black's bishop on g4 pins your knight to the queen. Black's last move, g6, wasted time. The pin is not as strong as it looks. It is named after Légal, a French master of the 1700s. About 17,000 rated games on Lichess have reached this position.
Nxe5! The knight takes a pawn and leaves the queen to the bishop. Taking the queen loses at once.
After Bxd1, Bxf7 check drives the king to e7, and Nd5 is checkmate. Two knights and a bishop beat the whole black army.
Recap.
A pin is only real if the piece behind it matters more than mate.
With a bishop on c4 aiming at f7, Nxe5 can ignore the pin.
After Bxd1, Bxf7 check and Nd5 mate.
If Black takes the knight instead, Qxg4 wins a pawn.
What you practise
First play the line. You are White: play the moves of the Philidor Defence, up to the moment of the sacrifice.
Your turn: find the sacrifice. The bishop on g4 pins your knight. Ignore the pin, and play for mate.
Black does not take the queen. Black takes your knight with the pawn instead. The bishop on g4 is now loose.
Worked examples
First play the line. You are White: play the moves of the Philidor Defence, up to the moment of the sacrifice. Good. Black answers g6. Now the position is ready for the sacrifice.
Your turn: find the sacrifice. The bishop on g4 pins your knight. Ignore the pin, and play for mate. That is Légal's mate. Bxf7 check, Ke7, and Nd5 mate. The pin on f3 was a bluff.
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