An x-ray attack (or simply x-ray) describes a long-range piece that targets or defends something standing behind an enemy piece lined up on the same file, rank, or diagonal. Even though it looks blocked, the piece keeps exerting real influence: if the blocking piece moves or disappears, the line opens instantly.

X-ray attack and x-ray defense

The motif shows up in two forms. On attack, a piece targets something through an enemy piece: if that piece steps aside, the target falls right away, which makes it less free to move than it looks. On defense, a piece virtually protects a square or a pawn through an enemy piece: if the opponent captures what looked undefended, the x-raying piece recaptures immediately.

Example: a rook defends its pawn through the enemy rook

The rook on a1 looks cut off from the pawn on a7 by Black's rook on a4, but it already x-ray defends the pawn. 1...Rxa7 2.Rxa7 proves it.

White’s rook on a1 looks cut off from the pawn on a7 by Black’s rook sitting on a4. But it’s already defending it “through” that rook: the moment Black plays 1…Rxa7 to grab the pawn, the file opens up completely, and 2.Rxa7 recaptures the black rook right away. The pawn, seemingly isolated, was actually protected the whole time by that x-ray.

Using the x-ray in your own games

Before assuming an enemy piece is completely free to move, or that a pawn is totally undefended, always check what’s standing behind it on the same line. This simple habit prevents plenty of mistakes in rook endgames, where the motif shows up especially often, and it can also reveal attacking chances your opponent hasn’t noticed.

Frequently asked questions

Is an x-ray the same thing as a pin?

No, even though both motifs involve three pieces lined up. In a pin, the middle piece is immobilized because moving it would expose a more valuable piece behind it. In an x-ray, the middle piece is free to move, but doing so instantly changes the balance of power on the line.

Does the x-ray only work with rooks?

No, queens and bishops can create this motif just as well, as long as they share a file, rank, or diagonal with an enemy piece and a target further along it. X-rays on diagonals are very common in same-colored bishop endgames.

How do I spot an x-ray during a game?

Mentally scan every open file, rank, and diagonal (even partially blocked ones) and ask yourself what’s sitting at the far end. If one of your pieces ends up lined up with an enemy target beyond some other piece, you’re probably looking at an x-ray worth exploiting.