Attack

An attack describes the squares on which a piece has capturing power. An opposing piece on one of those squares is attacked even when no capture is made on the current turn. The attack depends on the piece's movement pattern and on any pieces blocking its path.

Under the formal rules, a piece can attack a square even when it is pinned, meaning that moving it would expose its own king and make the move illegal. This distinction matters because a king may not enter an attacked square and because castling, the combined king-and-rook move, may not cross an attacked square.

Pawns show the difference between movement and attack especially clearly: they advance straight forward but attack one square diagonally forward. Rooks, bishops, and queens attack along lines but cannot pass through intervening pieces. Many tactics, such as a fork, one move that attacks two or more targets, are built from this geometry.