Battery

A battery is a formation of two or more rooks, bishops, or queens aligned on a vertical file, a horizontal rank, or a diagonal. Common examples are two rooks on one file, a queen with a rook, or a queen with a bishop. The front piece acts directly while the piece behind it reinforces the same direction.

A battery builds pressure, but it does not guarantee a gain by itself. Its value depends on the target at the end of the line, the pieces blocking the route, and whether the opponent can exchange one of the aligned pieces. Order also matters. On a diagonal toward the king, for example, placing the queen in front of or behind the bishop can change which captures and deliberate piece offers work.

The formation often prepares other ideas. The front piece may move and produce a discovered attack, or both pieces may control squares around the king and help form a mating net. A battery can therefore be a lasting source of pressure or the starting point of an immediate sequence of threats and captures.