The X-ray attack: seeing through a piece

A piece can "aim" at a square or another piece through something standing in between, as if seeing right through it. This tactical motif changes how you calculate a trade.

Key takeaway

A piece can act through another one on the same line: unlike a pin, which directly threatens the piece in front, an X-ray is pressure that only reveals itself once an exchange happens.

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The two queens face each other through the black pawn on d5: if a trade happens on that square, each queen is already lined up to recapture, as if it could see straight through the piece in between.

A pin and a skewer immobilize or directly target a specific piece. The X-ray attack is different: a piece aims at a square or a more distant piece through another piece, friendly or enemy, sitting in between, without threatening it directly for now.

The idea

This shows up most often on a file or diagonal shared by two heavy pieces (queens, rooks), with something sitting between them. Neither piece attacks the other yet, but they're already lined up: the moment the piece in the middle disappears, they face off directly.

Look at the diagram

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The two queens face each other through the black pawn on d5: if a trade happens on that square, each queen is already lined up to recapture, as if it could see straight through the piece in between.

Here, White's queen on d1 and Black's queen on d8 are separated by a black pawn on d5. As long as the pawn stays there, neither queen attacks the other directly. But if that pawn were captured or advanced, the two queens would instantly face each other on the d-file: each one was already "seeing" that square through the pawn.

Why it matters in practice

Spotting an X-ray relationship helps you calculate whether a capture sequence is actually safe. Before trading on a contested square, always check what's lined up behind it on the same file or diagonal: a piece can be waiting there, ready to recapture, well before it looks involved.

Did you know?

This pattern is especially common on open files and long diagonals with major pieces facing off, and it's a key part of correctly calculating exchange sequences several moves deep.

Key takeaways

✓X-ray = pressure through a piece, distinct from a pin or a skewer
✓Most common on files and diagonals with heavy pieces lined up
✓Always check what's "behind" a piece before trading on a contested square

Check your understanding

What sets an X-ray attack apart from a pin?