Gegenchecks

Gegenchecks, or counterchecks, are a chess tactic in which a player responds to a threat against their own king by delivering a check to the opponent's king in the same move. The defining condition is that the move must remove the immediate danger to the player's king and leave that king safe after the move. This makes counterchecks a defensive weapon that turns into an attack.

Counterchecks can occur in direct form, where the moving piece itself checks the opponent, or in discovered form, where the move opens a line of attack by another piece while parrying the threat. A countercheck is a legal reply only if the player's own king is not still in check after the move; otherwise the move would be illegal. The tactic relies on the opponent’s last move creating a position in which a counterattack is possible.

In practice, counterchecks are more common in problem composition and endgame studies than in everyday play. Composers use counterchecks to force lines, create surprising mates, or demonstrate the idea of turning defense into offense. They illustrate the principle that a defensive move can simultaneously assert initiative.

Etymology and usage: Gegencheck is the German term for the concept, with countercheck as the standard English equivalent. While the concept is widely recognized in chess literature, the exact term may vary by language. Counterchecks are related to but distinct from double checks; the former emphasizes the defensive turn, while the latter refers to a single move that gives check in multiple ways.