X-ray (chess)

In chess, an x-ray or x-ray attack is a tactic where a ranged piece supports a friendly piece "through" an enemy piece. It is different from a skewer, pin, or line clearance, with each of which it is often confounded.

Chess diagram|=
tright|
=8 |rd| |bd|qd| | |rd| |=7 |pd|pd| | | |pd|kd| |=6 | | | | |pd| |pd| |=5 | | |pd| | | |bd| |=4 | | | |pl| |bl|nl| |=3 | | | | | | | |ql|=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
Magrin - Sawij, Spain 1968

In the diagram on the right, White's major pieces (queen and rook) have taken control of the h-file, but Qh7+ allows the king to escape to f8. Instead, White wins with 1. Qh6+! Bxh6 2. Bxh6+ Kh7 3. Bf8+ Qh4 4. Rxh4#. Here (after 1. Qh6+), the white bishop on "f4" supports White's queen on h6 "through" the Black bishop on "g5".

Moves

Chess diagram|=
tright
Qh6!
=8 |rd| |bd|qd| | |rd| |=7 |pd|pd| | | |pd|kd| |=6 | | | | |pd| |pd|ql|=5 | | |pd| | | |bd| |=4 | | | |pl| |bl|nl| |=3 | | | | | | | |oo|=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
White: queen to h6; check

Chess diagram|=
tright
Bxh6
=8 |rd| |bd|qd| | |rd| |=7 |pd|pd| | | |pd|kd| |=6 | | | | |pd| |pd|bd|=5 | | |pd| | | |xo| |=4 | | | |pl| |bl|nl| |=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
Black: bishop takes queen on h6 removes checking piece

Chess diagram|=
tright
Bxh6+
=8 |rd| |bd|qd| | |rd| |=7 |pd|pd| | | |pd|kd| |=6 | | | | |pd| |pd|bl|=5 | | |pd| | | | | |=4 | | | |pl| |oo|nl| |=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
White: bishop takes bishop on h6; check

Chess diagram|=
tright
Kh7
=8 |rd| |bd|qd| | |rd| |=7 |pd|pd| | | |pd|xo|kd|=6 | | | | |pd| |pd|bl|=5 | | |pd| | | | | |=4 | | | |pl| | |nl| |=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
Black: king to h7 avoids check

Chess diagram|=
tright
Bf8+
=8 |rd| |bd|qd| |bl|rd| |=7 |pd|pd| | | |pd| |kd|=6 | | | | |pd| |pd|oo|=5 | | |pd| | | | | |=4 | | | |pl| | |nl| |=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
White: bishop to f8; check by rook@h1

Chess diagram|=
tright
Qh4
=8 |rd| |bd|xo| |bl|rd| |=7 |pd|pd| | | |pd| |kd|=6 | | | | |pd| |pd| |=5 | | |pd| | | | | |=4 | | | |pl| | |nl|qd|=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |rl|= a b c d e f g h
Black: Queen to h4 blocks check

Chess diagram|=
tright
Rxh4#
=8 |rd| |bd| | |bl|rd| |=7 |pd|pd| | | |pd| |kd|=6 | | | | |pd| |pd| |=5 | | |pd| | | | | |=4 | | | |pl| | |nl|rl|=3 | | | | | | | | |=2 |pl|pl|pl| | |pl|pl| |=1 |rl| | | |kl| | |oo|= a b c d e f g h
White: Rook takes queen on h4; checkmate by rook@h4 and bishop@f8

As a defense

Chess diagram|=
tright|
=8 |rd| |rl| | | |kd| |=7 |pd|pd| | | |pd|pd|pd|=6 | | | | |pd| | | |=5 | | | | | | | | |=4 | | | | |pl| | | |=3 | | | | | | | | |=2 |pl|pl| |rd| |pl|pl|pl|=1 | | |rl| | | |kl| |= a b c d e f g h
Black to move. After 1. Rc8+

The x-ray is also used for defensive purposes. In the second diagram, White has just given check with 1. Rc8+ and Black is in danger of being checkmated on the back rank. If Black responds 1. ... Rxc8??, play continues 2. Rxc8+ Rd8 (forced) 3. Rxd8#. Instead, Black's only saving move is to interpose immediately with 1. ... Rd8. After this play, Black's rooks on a8 and d8 guard one another by x-ray through the white rook on "c8". If the white rook captures one of the black rooks, the remaining black rook responds by recapturing on the same square, and Black is safe from checkmate.

ee also

*Chess tactics

References