Double attack — what it means in chess
Any single move creating two threats at once.
Any single move creating two threats at once.
A double attack is any single move that creates two threats at once. A fork is one kind — two pieces attacked by one piece — but the idea is broader: a move can threaten mate and a hanging piece together, or attack a piece while unveiling a second threat elsewhere. Two threats, one move, one reply available. That gap is where the material comes from.
The rule of thumb for finding double attacks is to count the loose pieces on the board — the ones with no defender, or defended only once. Every loose piece is a target waiting for a partner. A queen that can reach a square where it checks the king and eyes the loose bishop at the same time has found a double attack. So has a knight that lands on a square attacking a rook while covering a mating threat. Two threats, one reply. If you make a habit of scanning for undefended pieces the moment your opponent moves, the double attacks in a position start to volunteer themselves.
[[board startfen="4k3/4ppp1/8/8/1b6/8/8/3Q2K1 w - - 0 1" pgn="1. Qa4+ Kd8 2. Qxb4" caption="A double attack: one move makes two threats — here a check and a hit on the loose bishop." notes="White to move. The bishop on b4 is undefended, and the king is exposed. Qa4+ — two threats at once: check to the king on e8, and an attack on the loose bishop on b4. Black must answer the check first... ...and the bishop falls. Two threats, one reply available."]]
The fork is the double attack's most famous species; the discovered attack and the skewer are its geometric cousins.
The Endgame Society glossary defines more than 240 chess terms — rules, notation, tactics, strategy, pawn structures, endgames, and openings — in language a beginner can act on rather than dictionary shorthand.