Explanation

Having one of your pieces pinned can often be a disadvantage. In "Pin and win" and "Attacking the pinned piece" you saw how a pin can lead to material losses. Even if a pin does not win material, the pinned piece is usually restricted in its mobility, which can be a disadvantage. Occassionally though, you can turn the tables and use your opponent's pin to your advantage by moving with the pinned piece!

• In the first diagram, the black bishop is pinning the white rook against the king. This is an absolute pin. White is not allowed to move out of the pin, as it would put the white king into check.
• In the second diagram, the black bishop is pinning the white knight against the rook. This is a relative pin. Moving the knight out of the pin is allowed but would probably lose the rook.
• In the third diagram, the black bishop is pinning the white knight against the queen. The queen can operate on the same diagonal as the pin.

If you move the knight in the third diagram, it discovers an attack by the white queen on the black bishop. This discovered attack can win the game if the knight move comes with another threat. For example, the knight might move and give a check, enabling the queen to capture the bishop on the next move. The knight unpins, and Black's pin "backfires" into a discovered attack by White.

Examples

White can move the knight out of the pin with check: 1.Ng5+! The move discovers an attack by the white queen on Black’s queen. Now if 1...Nxg5 (or 1...hxg5) then 2.Qxg4, and if 1...Qxg5 then 2.Bxg5 Nxg5 and White has a winning material advantage of a queen for two knights.

Black can step out of the pin with 1...Bxc3! capturing a knight and attacking the rook on d2 with the bishop, and with a discovered attack on the rook on a4. To avoid further material losses, White must play 2.Rxc4 Bxd2, and Black is up a bishop for a pawn in the endgame.

Black can win by moving the knight out of the pin with 1...Nh3!, threatening checkmate on g1 and with a discovered attack by the black queen on White''s queen. White has no good defense to deal with both threats.

How to Spot an Opportunity to Unpin

If your opponent pins your piece against a piece that can operate on the same line as the pin, always look for ways to move the pinned piece to discover an attack. If you make a relative pin, always be careful and avoid your opponent's unpinning tactics.

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