Absolute and Relative Pins in Chess

The geometry of a pin

Pins require three elements on one rank, file, or diagonal:

1. a long-range attacking bishop, rook, or queen;
2. the pinned piece in the middle; and
3. a more important target behind it.

The attacker and hidden target must share a clear line except for the pinned piece. Knights, kings, and pawns can be pinned, but they do not create line pins themselves.

What is an absolute pin?

An absolute pin has the king behind the pinned piece. The middle piece may not make any move that exposes the king to attack, because leaving your own king in check is illegal.

In the diagram, the White bishop on b5 attacks along b5–c6–d7–e8. The Black knight on c6 blocks that diagonal in front of its king. A knight move would uncover check, so the knight cannot move away while the line remains unchanged.

The pinned piece may still have a legal move along the pin line if that move continues to shield the king or captures the pinning piece. Whether this is possible depends on the piece and geometry. “Pinned” does not always mean completely frozen.

What is a relative pin?

In a relative pin, the target behind the piece is not the king. It may be a queen, rook, checkmating square, or important defender. The pinned piece is legally allowed to move, but doing so may concede the target.

For example, a bishop may pin a knight to a queen. The knight can still move if it creates checkmate, wins the opposing queen, or gains enough compensation. Treat a relative pin as a tactical cost, not a legal prohibition.

Situational and tactical pins

Some pins are based on a task rather than raw piece value. A rook may be “pinned” to back-rank defense because moving it allows mate. A pawn may be tied to protecting a promotion square. These are not absolute rules of movement, but the tactical consequence can be just as forcing.

Name the target behind the piece. If you cannot explain what is exposed, the apparent pin may have no practical value.

How to exploit a pinned piece

A pin is usually the beginning of a tactic, not the result. Common follow-ups include:

• attack the pinned piece with a pawn;
• add another attacker while it cannot move;
• remove or distract its defenders;
• occupy a square the pinned piece normally controls;
• open the line further; or
• create a second threat against the hidden target.

Calculate whether the opponent can break the pin with check, capture the attacker, interpose another piece, move the king, or create a stronger threat.

How to break a pin

Defensive methods include:

• move the king away from the line;
• move the valuable target behind the pinned piece;
• attack or capture the pinning piece;
• block the line with another piece;
• defend the pinned piece enough to allow an exchange; or
• create a forcing counter-threat.

Ask whether breaking the pin is urgent. Spending several tempi to chase a harmless bishop may create more weaknesses than the pin itself.

A pinned piece still attacks squares

For king-move and castling purposes, a piece can still be considered to attack a square even when moving there would expose its own king. This detail prevents a king from capturing a “pinned” defender as though it had no influence.

Distinguish legal move from attacked square. The FIDE definition explicitly treats these concepts differently in king-safety rules.

Pins and exchanges

Capturing a pinned piece is not automatically profitable. Reconstruct every recapture. If a bishop pins a knight to a queen and then exchanges bishop for knight, the queen may simply recapture and the pin disappears with equal material.

The pin becomes valuable when it wins a tempo, damages structure, removes a defender, or creates a concrete second threat.

Common pin mistakes

• Calling every aligned piece pinned without identifying the target behind it.
• Treating a relative pin as if the piece cannot legally move.
• Forgetting that an absolutely pinned slider may move along the line in some positions.
• Capturing the pinned piece before adding enough pressure.
• Letting the opponent move the king and break the pin with tempo.
• Moving your king onto a square attacked by a pinned enemy piece.
• Ignoring a counter-check that makes the pin irrelevant.

Practice exercise

Find five pins in your own games. Label each absolute, relative, or situational. For every pin, write the hidden target, the opponent's best method of breaking it, and the concrete follow-up that would make the pin useful.

Then modify one diagram by moving the king away. Explain how an illegal knight move becomes legal when the absolute pin turns into a relative one or disappears.

Frequently asked questions

Can a pinned piece capture the pinning piece?

Yes, if the capture is legal and leaves its king safe. A relative pin never forbids the move; an absolute pin allows it when the attack on the king is removed.

Can a knight be absolutely pinned?

Yes. Because a knight cannot move along a line to keep blocking it, an absolute line pin usually prevents all knight moves until the pin changes.

Does a pinned piece defend another piece?

It may attack that square for king-safety purposes, but it may be unable to make a legal recapture. Evaluate the exact final position.

What to learn next

Apply pins when protecting pieces and counting effective defenders, then compare the reversed line geometry of a skewer.

Browse the chess tactics lessons for more forcing patterns.

Rules reference: FIDE Laws of Chess, Articles 3.1.3 and 3.9.