A pin occurs when a bishop, rook, or queen attacks a piece that has something valuable behind it on the same line. Moving the front piece would expose the rear target. The important information is the entire line, not simply the attacked piece.
Absolute and relative pins
If the rear target is the king, the pin is absolute: the front piece cannot make a move that exposes its king to check. A pinned rook may still move along the pinning line or capture the attacker if that keeps the king safe.
If the rear target is a queen or rook, the pin is relative. The front piece may legally move. Doing so might even be strong if it creates checkmate or a larger threat. Do not confuse “usually costly” with “illegal.”
Add pressure to the pinned piece
A pin can turn a protected piece into a target for a pawn advance or another attacker. Before piling on, ask whether the defender can unpin by moving the king, interposing a piece, or exchanging your attacker.
A subtle rule matters around kings: a piece still attacks squares for king-movement purposes even when moving that piece would expose its own king. Do not let your king capture something merely because its apparent defender is pinned.
Explain what is restricted
Instead of “the knight is pinned,” say “the knight cannot leave this file because the rook would check the king.” That precision helps you see which knight moves are impossible and which defensive resources remain.
A familiar pin in a developing position
Read all 7 moves and their reasons
- 1. d4 White occupies d4 and releases the c1 bishop.
- 1… d5 Black claims central space in reply.
- 2. c4 The c-pawn attacks d5; a capture would pull Black’s central pawn toward the flank.
- 2… e6 Black supports d5 and opens the f8 bishop, while restricting the c8 bishop.
- 3. Nc3 White adds pressure to d5 and develops.
- 3… Nf6 Black develops a knight that helps defend d5.
- 4. Bg5 The bishop develops and pins the f6 knight to the queen; Black must consider the pressure along this diagonal.
After Bg5, follow the diagonal from the bishop through f6 and e7 to d8. The black knight on f6 stands in front of its queen. This is a relative pin: moving the knight is legal, but may allow Bxd8. White has developed a bishop while making that knight less free to choose its next square.
Do not exaggerate the restriction. Black can develop the f8 bishop to e7, placing another piece between the knight and queen and changing the diagonal’s meaning. Black might also move the queen or challenge the bishop. A pin is a feature of the current arrangement, not a permanent property attached to a piece.
The knight still defends d5 unless a particular capture on d5 would make its recapture tactically unacceptable. Counting attacks and defenders without considering their legal and tactical obligations gives unreliable answers.
Why the pinned piece still matters to a king
FIDE’s attack rule treats a piece as attacking a square even when moving it would expose its own king. Consequently, your king cannot walk onto a square attacked by a pinned knight. The pin may prevent the knight from making an ordinary move, but it does not create a safe king destination on one of its attacked squares.
Keep those questions separate: “Can this knight legally move?” and “May my king occupy a square this knight attacks?” They serve different purposes. The first helps calculate exchanges; the second tests whether a king move is legal. This distinction is especially important when trying to capture a protected piece near the enemy king.
Your turn
Pause. Think. Explain.
Can a relatively pinned knight move away from a queen if the knight's move gives checkmate?
Reveal the explanation
Yes. A relative pin does not make the move illegal. If the knight's move is legal and checkmates, the exposed queen no longer matters.
Sources & further reading
Original explanation and exercise by ChessTrainer Academy. Linked sources support the historical, rules, or product details.
Take it to the board
One idea. A whole game to find it in.
Choose a complete game, hide the next move, and explain your candidate before you reveal it.
Explore the game library