Deflection

Deflection means forcing an enemy piece to leave an important defensive duty. That duty may be protecting another piece, guarding a square near the king, blocking a line, or stopping a pawn from reaching the last rank and becoming another piece. Once the defender moves away, the attacker carries out an idea that was previously impossible.

The deflecting move may be a capture, a check, meaning a direct attack on the king, a threat, or a sacrifice, meaning the deliberate offer of a piece in exchange for a greater gain. The defender's reply must be restricted. If it can decline the offer or move to another square while keeping the defense, the deflection does not work.

An overloaded piece, one burdened with several duties, is a natural target. The idea is also close to a decoy: both make an enemy piece move, but deflection emphasizes the duty it abandons, while decoy usually emphasizes the troublesome square to which it is drawn.