Discovered attack

A discovered attack happens when a piece moves out of the way and uncovers an attack from a long-range piece — bishop, rook, or queen — that was lined up along the same file, rank, or diagonal. The piece that moves and the piece that does the attacking are two different units, but the move makes them both threats in a single tempo.

The motif’s power comes from the double threat. The moving piece can attack something on its own — the discovered piece behind it threatens something different. The opponent must answer two attacks with one move, which is rarely possible. If the moving piece also delivers check (a discovered check), the result is usually decisive: the opponent must address the check while the discovered attacker takes whatever it pleases.

A particularly devastating version is the double check — both the moving piece and the discovered piece deliver check at the same time. The defender cannot block both checks; the king must move. This often allows the attacker to win significant material or deliver mate.

Discovered attacks are most commonly set up by knights and pawns, since these pieces move in ways that don’t require capturing the piece they unblock. A typical setup is bishop on b3, knight on c4: the knight moves anywhere with tempo, the bishop’s attack on f7 is revealed. The defender, faced with both the knight’s threat and the bishop’s, has no satisfactory reply.