Double attack

A double attack occurs when one move creates two simultaneous threats. Its power comes from the fact that an ordinary reply often solves only one, allowing the other to win material, checkmate, promote a pawn, or achieve another concrete gain.

The threats do not have to be direct attacks by the same piece. A queen may give check while attacking a rook; a pawn may threaten promotion and a capture; or a piece may move with its own threat while uncovering another piece's attack. The last form is related to a discovered attack.

A fork is a kind of double attack in which one piece directly attacks two or more targets. Every fork creates multiple attacks, but double attack is broader because one threat can be indirect, such as checkmate on the next move.

Not every double attack wins. The defender may find one move that answers both threats by moving with check, capturing the attacker, blocking one line while protecting the other target, or creating an even more urgent threat. Calculation must continue until such a multi-purpose defense has been ruled out.