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Ponderchess / Glossary

Skewer in chess

A skewer is an attack along a line on a valuable piece which, when it moves out of the way, exposes a less valuable piece behind it to capture. It is the reverse of a pin, and it is most deadly when the front piece is the king.

White to move. The black king on d5 and the queen on b7 share the long light-squared diagonal. Bf3+ checks the king, which must step off the line, and then Bxb7 wins the queen. The rook on c1 keeps the king off c4 and c5, and c6 is still on the bishop's diagonal.1.Bf3+ Ke5 2.Bxb7

How a skewer works

Like a pin, a skewer needs a line piece: a bishop, rook or queen. The difference is the order of the targets. In a skewer the more valuable piece is in front, so it is the one that has to move, and the piece behind is left hanging.

When the front piece is the king, the skewer comes with check and the king must step aside. When the front piece is a queen or rook, the skewer is relative: the owner may choose to give up the front piece instead, but either way material is lost.

Typical skewers

The most common is a rook or queen check along a rank or file that hits the king and an undefended rook or queen behind it. Skewers are especially frequent in endgames, where kings and rooks stand on open lines, and many rook endings near the promotion square turn on a check that skewers the king and the enemy rook.

Bishops skewer along diagonals, often catching a king and queen on the same colour of square. A long diagonal such as h1-a8 or a1-h8 is a frequent stage.

How to spot and avoid skewers

Whenever two enemy pieces share a line, ask whether you can attack the front one in a way it must answer. Checks matter most, because the king has to move and gets no time to protect the piece behind.

To avoid skewers, do not leave the king and an undefended heavy piece on the same rank, file or diagonal, and keep pieces protected so that the piece behind is not won for free.

Common mistakes

  • Placing the king and queen on the same diagonal when the opponent still has the bishop of that colour.
  • Answering a skewer of two rooks by moving the front one without checking whether the one behind is protected.

Questions about skewer

Is a skewer the opposite of a pin?

In a sense. Both attack two pieces on one line, but in a pin the less valuable piece is in front and cannot move safely, while in a skewer the more valuable piece is in front and must move.

Which pieces can skewer?

Bishops, rooks and queens, because a skewer works along a line. Knights, pawns and kings cannot skewer.

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