X-Ray Attacks in Chess
An x-ray attack occurs when a piece exerts influence "through" another piece, attacking a square that's currently blocked but would become a direct attack if the blocking piece moved. X-ray attacks are subtle because the threat isn't immediately visible, but they're extremely common in practical play and create many tactical opportunities.
What is an x-ray attack
An x-ray occurs when a long-range piece (queen, rook, or bishop) attacks a square through an intervening piece. Example: A white rook on e1 and a black queen on e4, the rook "x-rays" through the queen to the e8 square. If the queen moves, the rook controls e8. X-rays create latent threats that become real when the intervening piece moves. This concept is related to skewers and discovered attacks.
X-ray in defence
X-ray defences are equally important: a rook "x-rays" through a piece to defend a square behind it. This means that even though the rook appears blocked, it's actually providing indirect defence. Example: White's rook on d1 behind White's queen on d3, the rook x-ray defends d1 even though the queen is in the way. If the queen is captured, the rook recaptures, maintaining control of the d-file.
X-ray in the endgame
X-ray concepts are critical in rook endgames. The "x-ray defence" in R+P endings, where the defending rook checks from behind, "x-raying" through the advancing pawn, is one of the most important endgame techniques. Understanding x-ray relationships between rooks and passed pawns separates strong endgame players from average ones.
Spotting x-rays
Training exercise: In any position, trace the lines (files, ranks, diagonals) from each long-range piece and note what squares they would control if the intervening pieces were removed. This "x-ray scan" reveals hidden tactical possibilities. With practice, you'll start seeing x-ray relationships automatically. Practice on the puzzle trainer.