X-ray attack

The idea

A long-range piece strikes through an enemy piece — as if x-raying it. At the same time a second piece of yours attacks the same target, but from a different direction.

So the enemy piece only pretends to be a defender. It is transparent: remove it, and the blow arrives.

How it looks

Your rook looks up the file at a square next to the enemy king, but his rook stands in the way — it seems to be guarding that square. At the same time your queen attacks the same square from another direction, along the diagonal.

The queen goes there with check, the enemy rook is forced to capture — and in doing so steps off the file itself. Your rook, which was looking through it all along, recaptures on the same square with mate.

How to spot it

When counting defenders of a square, include not only those attacking it directly but also those looking through a piece. Such defenders and attackers are easy to miss: the line seems blocked, when in fact it is simply waiting.

Important: you must be able to remove the obstruction yourself — by capture or by force. Your opponent will not clear the x-ray line voluntarily.

Often confused with

A battery. In a battery both of your pieces stand on one line, one behind the other. In an x-ray they hit the target from different directions, and one of them is blocked by an enemy piece.