The Pin

A pin is a straight-line attack that freezes an enemy piece because something more valuable stands behind it. Move the front piece and the back piece dies. Only bishops, rooks, and queens can pin, because only they attack in lines.

Absolute vs relative

• An absolute pin has the king behind the pinned piece. Moving the front piece is literally illegal. The pinned piece is a statue.
• A relative pin has a queen or rook behind. The front piece CAN move, it just usually should not. “Usually” is where the tricks live, so never assume a relative pin is a lock.

The pin is not the payoff

Beginners pin a knight and feel clever. The payoff comes from the follow-up: pile on the pinned piece. It cannot run, so every new attacker tips the math. A pinned piece defended once and attacked twice is already gone, it just has not been removed yet.

The classic bite

Bg5 pinning a knight against the queen looks harmless until h4 and g5 arrive, or until the knight’s defender gets traded off. Count attackers versus defenders on the frozen square, not on the whole board.

Escaping pins

Break the line: block with a lesser piece, chase the pinning bishop with pawns, unpin by moving the valuable piece behind, or counterattack something bigger. The worst response is pretending the pin is not there. It does not go away. It compounds.