ChessRanger
Rules & notation

Interpose

to block a check

Blocking a check by placing a piece between the checking piece and the king.

There are only three legal replies to a check: move the king, capture the checker, or interpose a piece to block the line. Interposing is only possible against a line piece (rook, bishop, queen) — you can't block a knight check or a contact check.

The interposed piece is often pinned afterwards, so choosing what to interpose can matter as much as that you can.

Why it matters

Knowing that interposing is an option — and when it isn't (knight and double checks) — is basic to escaping checks and to setting them.

The mistake everyone makes

Trying to block a knight check or a double check, both of which can only be answered by moving the king.

Related terms

Check
An attack on the king that must be answered immediately.
Discovered check
A check delivered by moving a piece out of the way of a rook, bishop, or queen behind it.
Double check
Two pieces give check at the same time; the king must move.

See Interpose in your own games

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