X-ray attack

An X-ray attack occurs when a rook, bishop, or queen exerts a threat or defense through a piece standing on the same line. These pieces cannot jump, so the intervening piece still blocks an immediate move. The X-ray metaphor means that pressure continues beyond the blocker and may become effective when the position changes.

Picture a rook, an intervening piece, and a target aligned on one vertical file. If the middle piece moves or is captured, the rook reaches the target behind it. This relationship can support an attack, provide indirect defense, or prepare a sequence of captures. When the blocker is a friendly piece that moves away and reveals the attack, the idea becomes a discovered attack.

Terminology is not completely uniform. Some sources use X-ray for any long-range influence through another piece; others reserve it for particular indirect attacks or use it near the idea of a skewer, where a valuable front piece is attacked and exposes another piece after moving. It is therefore better to identify the actual geometry than to rely only on the label.