X-Ray Attack: Seeing Through an Enemy Piece
An x-ray is the attack or defence a bishop, rook or queen exerts through an enemy piece, which takes effect the moment that piece moves off the line.
How an x-ray works
Normally a piece in the way blocks a line. But when the blocking piece is an enemy piece that is likely to move, often to recapture, the line will open at exactly the right moment. A rook behind an enemy rook on the same file is, in effect, also guarding the squares beyond it.
This changes how you count exchanges. Suppose your queen captures on a square defended by an enemy rook, and your own rook stands behind that enemy rook on the same file. When the enemy rook recaptures, it leaves the line, and your rook now sees the square. You had two attackers all along, even though one of them looked blocked.
The term is also used for skewer-like attacks, where a piece attacks something through an enemy piece in front of it. The common thread is the same: lines do not stop at the first piece if that piece can be forced to move.
Where x-rays show up
Doubled rooks and queen-and-rook batteries on open files are the usual source. When both sides stack heavy pieces on the same file, the order of pieces on that file decides who wins the trades. The same applies on diagonals with queen and bishop.
X-rays are especially common on the back rank. A queen sacrifice on the eighth rank, met by a rook recapture, can open a file for another rook to give mate.
Common mistakes
Players miscount exchanges by only counting pieces that touch the square right now. Always continue the line past the first piece and ask who is behind it. If you are the defender, remember that recapturing with a piece that sits on a line can open that line for your opponent. The x-rays you miscount in your own games are the ones worth drilling.
How to spot it
- On contested files and diagonals, list every piece in order, both colours.
- Count attackers behind enemy pieces, not just the first one.
- Ask which recapture would open a line for your pieces.
- Look for sacrifices on the back rank backed by a rook behind.
- Before recapturing, check what your moving piece uncovers.
Try one
Work it out from the diagram first, then play it on the board or open the solution.
6
3
Example 1
White to move and mate.
Show solution
31.Qxf8+ Rxf8 32.Rxf8#
The rook on f8 looks safe because the rook on f6 defends it, but White's rook on f2 stands behind the f6 rook on the same file. Qxf8+ gives check, and since the queen covers g8, Rxf8 is Black's only legal reply. That recapture clears the f-file, and Rxf8# is mate: the pawns on g7 and h7 box in the king, and the queen on h6 cannot reach g8.
Position from a real game, via the Lichess puzzle database.