I’m sure you all know about Legal’s Mate (or, if you prefer, Legall or Legalle, with or without an acute accent). It’s named after François Antoine de Legall de Kermeur (1702–92), a French chess player who taught Philidor and was probably, until he lost a match to his pupil in 1755, the strongest player in the world. Sadly, the games of that match are not extant: all we have of his play is the one game with the mate that bears his name.
Here’s an example from the RJCC database: Ray Cannon giving a simul back in 1987.
Black resigned, seeing that 8.. Ke7 9. Nd5 was checkmate. He would have been better advised to capture with the pawn rather than the knight on move 6.
There are, as you would imagine, many games on my database where one player unwittingly moves the pinned knight, losing the queen. Beginners will see the attack on the knight, decide they don’t want to lose it (even though it’s defended twice) and move it away. Alternatively, as in the next game, a more experienced but impatient player will get excited about the idea of creating a threat and forget to ask himself the Magic Question.
Of course, this is a really important topic that we need to teach to young children.
Firstly, they have to understand the pin, recognise the typical position type and be aware that if they move the knight their opponent will be able to capture their queen.
Then they need to learn that sometimes, but not very often, they will be able to move the pinned knight with impunity because they, like Sire de Legall or Ray Cannon, will have a mate at the other end of the board. Apart from its practical merit, it’s always good to show children queen sacrifices. There’s a section on Legal’s Mate in Move Two!.
But there are two possible problems that can arise. The first one happens when they find the mate they’d planned was illusory. One of my earliest coaching experiences was a game at RJCC where, after we’d given the class a lesson on Legal’s Mate, one player did just this. It might possibly have been this game:
If this was the game I’m thinking of, Black played Ng4 fully aware that White could take the queen but hoping that he had a mate in reply.
Another thing that can go wrong is that the mate’s there but the sacrificer hasn’t considered what happens if his opponent doesn’t take the queen.
Here’s the start of another RJCC game from the same period:
The mate’s there OK if Black takes the queen on move 6, but he unsportingly captured the knight instead when White had nothing for the piece.
Failing to check for this sort of thing is not recommended, but in another RJCC game nearly 20 years later Black got away with his indiscretion:
A little bit of thought would have persuaded White to play 12. Nxe4, leaving him a piece ahead. So there you have it. Teach your pupils about Legal’s Mate: it’s an important part of their chess education. Don’t forget to provide some Legal aid as well. Teach them to ensure that the mate is actually there if their opponent snaps at the bait, and to check what happens if their opponent doesn’t take the queen. Perhaps a worksheet could be produced where the students have to tell you whether or not the unpinning sacrifice works.