Pin and Skewer: the tactics that punish two pieces on one line

A pin and a skewer are the same geometry seen from opposite ends. In both, a line piece (bishop, rook or queen) finds two enemy pieces lined up on the same file, rank or diagonal. In a pin, the cheap piece is in front and cannot move without handing over the one behind it. In a skewer, the valuable piece is in front, has to run, and gives up what stood behind it.

The pin: the piece that cannot move

A pin needs three things on one straight line: your line piece, an enemy piece, and behind it something the opponent cannot afford to lose. The piece in the middle stays on the board but loses its mobility, and a piece that cannot move is worth less than the point table promises. Knights, pawns and kings never pin: none of them attacks along a line.

Absolute or relative

Everything depends on who waits behind. If it is the king, the pin is absolute: moving the piece in the middle would leave your own king in check, and the rules forbid it. It is illegal, not a matter of judgement. If a queen or a rook is behind, the pin is relative: the move exists and only costs material, so the player decides the price.

A relative pin worth knowing turns up on move four of the Queen's Gambit Declined: once Black has played 2...e6 the e7 square is empty, and the bishop on g5 looks straight through the knight on f6 at the black queen.

How to exploit a pin

A pinned piece is a stationary target. Attack it more times than the opponent can defend it, start with your cheapest attacker, and before you pile on, take away the move that would break the pin.

• Attack it again, ideally with a pawn. It cannot run, so every new attacker is pure profit.
• Attack the piece behind as well. If it leaves the line you gain a tempo; if it cannot leave, the pin holds.
• Treat the pinned piece as if it were not there. A knight pinned against its king defends nothing: it cannot capture.

Go back to the first diagram. The obvious move, 1.Bxc6+, only trades a bishop for a knight. The strong move is 1.d5, hitting a second time a piece that cannot run. 1...Kd7 defends the knight, but 2.dxc6+ comes with check and the king cannot recapture, because c6 is still covered by the bishop. Anything else allows 2.dxc6 for free.

This is not a laboratory position. In the Steinitz Defence of the Ruy Lopez (1.e4 e5 2.Nf3 Nc6 3.Bb5 d6), the move ...d6 clears d7 and the knight on c6 is pinned the same way, with no legal move. White plays 4.d4 and 4...Nxd4 is not even allowed. The main reply is 4...Bd7, stepping the bishop in between and ending the pin.

How to break a pin

Being pinned is not a life sentence. There are five ways out, and the best one solves the problem and achieves something else along the way.

• Move the piece behind. King off the diagonal, queen off the file, and the front piece walks again.
• Interpose. A piece between the pinned one and the one behind settles it, as 4...Bd7 does in the Steinitz.
• Chase the pinner away. ...h6 and ...g5 push the bishop off g5; a pawn attacking the pinner clears the line.
• Capture the pinner. The permanent cure: trading a knight for the pinning bishop clears the line for good.
• Counterattack. A bigger threat forces the opponent to deal with that first.

If none of those is available, defend the pinned piece again: the pin stays, but piling on gets expensive.

The skewer: a pin in reverse

In a skewer the valuable piece is the one in front. You attack it, it has to move, and it hands over whatever stood behind it. A pin nails a piece down; a skewer drives a piece away and charges a toll for the trip.

The check removes the choice. The king has six squares and none of them saves the rook: whatever it plays, 2.Bxh8 follows, and a three point bishop has collected a five point rook. A skewer with check is the strongest version: the reply is forced. Without check, the defender sometimes escapes with a counterattack.

Skewers decide endgames. In rook endings the pattern never changes: line your rook up with the enemy king and rook, give check, take the rook. In pawn races, the first player to promote often wins by skewering the enemy king and its new queen.

How to spot both over the board

Pins and skewers appear when two enemy pieces line up. The habit worth building is to hunt for alignments rather than for moves.

• King and queen on the same diagonal or file: a single bishop or rook move can pin or skewer them.
• A heavy piece behind a light one: a rook behind a bishop, a queen behind a knight.
• Before you capture, ask who defends the target and whether that defender is pinned.
• After every exchange, read the lines again: pins and skewers are born when a piece steps out of the way.