Interposing

Interposing means placing one of your own pieces on the line between an enemy piece and your king to block a check.

Category
Rules
Also in
Tactics
Difficulty
Beginner
Also known as
Interposition, Blocking, Blocking the check, Interpose

Interposing is the defensive move of placing one of your own pieces directly on the line between an enemy sliding piece and your king, cutting off the check.

Only checks from rooks, bishops, and queens can be blocked this way. Knights deliver checks that cannot be intercepted, and pawn checks are likewise unblockable.

The interposing piece must land on an empty square along the attack line. If that square is protected by the attacker or its supporters, the interposer may be captured on the next move, often renewing the check.

{"v":1,"type":"board","orientation":"white","fen":"4k3/8/8/8/8/8/4R3/4K3 w - - 0 1","arrows":[{"from":"e8","to":"e1","color":"bad"}],"highlights":[{"square":"e4","color":"neutral"}],"caption":"White can interpose on e4 to block the check.","alt":"White king on e1 checked by black rook on e8 along the e-file. Square e4 is highlighted as a possible interposition square."}

In the diagram above, the white rook on e2 can move to e4 (or e3, e5, etc.) to break the line of attack. The choice of square matters: placing the rook too close to the enemy piece may allow an immediate capture, while moving it farther away may expose it to other threats.

Interposing is often the only legal way to resolve check when the king has no safe flight squares and the checking piece cannot be captured. It frequently appears in back-rank or file-based mating patterns where the defender must buy a single tempo to reorganise.

Frequently asked questions

What does interposing mean in chess?
Interposing is the act of placing one of your own pieces on the line between an enemy sliding piece and your king to block a check.
Which pieces allow interposition to stop a check?
Only checks from rooks, bishops, and queens can be blocked by interposition, since they attack along clear lines.
Can a knight check be stopped by interposing a piece?
No, knight checks cannot be blocked because knights jump over pieces and do not use a sliding line of attack.
Where must the interposing piece be placed?
It must move to an empty square that lies directly between the attacking piece and the king.
What often happens after a piece interposes?
The attacker may capture the new piece on the next move, which can renew the check if the capturer is protected.

See also

  • Blockade — A blockade is the occupation of the square directly in front of an enemy passed pawn by a piece, typically a knight, which halts its advance, controls surrounding squares, and converts the pawn into a target.
  • Capture — Capture is the act of moving your piece onto a square occupied by an opponent's piece and removing that piece from the board.
  • Check — Check occurs when a player's king is under direct attack by an opponent's piece and must be resolved on the next move.
  • Checkmate — Checkmate ends the game when a king is in check and has no legal way to escape by moving, capturing the attacker, or blocking the attack.
  • Discovered Check — A discovered check occurs when one piece moves aside, revealing an attack on the enemy king from a second piece positioned behind it on the same line.
  • Double Check — A double check occurs when two pieces simultaneously check the enemy king, most often via a discovered check in which the moving piece also attacks the king.

Referenced by

  • Cross Pin — A cross pin is a tactic in which one piece pins two enemy units along intersecting lines, so that either may be captured if it moves.
  • Dovetail Mate — A dovetail mate is a queen mate against a king whose own pieces block its flight squares in a dovetail-like pattern, typically on the edge of the board.
  • Knight Jumper — A knight jumper is another name for the chess knight, the only piece that moves in an L-shape and jumps over any pieces in its path.
  • Perpetual Check — A perpetual check is a drawing tactic in which one player forces an unending cycle of checks that the opponent cannot escape without allowing repetition.

Written by Chesswick.

Reviewed by Maria Russell.

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About the reviewer

Maria Russell

Maria didn't grow up dreaming of chess. She grew up dreaming of getting through bedtime without a meltdown, and chess just happened to be the thing that worked.

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