A battery is two pieces of the same colour stacked on one line — file, rank, or diagonal — so they support each other and bring doubled force to bear.
Lining up a queen and bishop on a diagonal, or a queen and rook (or two rooks) on a file, multiplies their pressure: the lead piece can capture or check while the piece behind backs it up, so a single defender is no longer enough.
Batteries are how you break through. Doubled rooks on an open file can crash onto the seventh rank; a queen-and-bishop battery aimed at h7 is the spearhead of many kingside attacks.
A battery is also the engine behind discovered attacks and windmills: when the front piece moves, the rear piece’s line springs open. Stacking your heavy pieces on the right line is a basic building block of attack.
Two pieces lined up on the same file, rank, or diagonal so they reinforce each other and apply doubled pressure along that line.
Queen plus bishop on a diagonal, queen plus rook on a file or rank, and two rooks doubled on a file — all classic attacking formations.
BetterChess is a practice tool — we make no guarantee you'll reach 1800 or any rating. Definitions are standard chess terminology; every diagram position is checked legal with the same engine the board runs.