Infantry square
An infantry square, also known as a hollow square or square formation, was a musket-era historic close order formation used in combat by infantry units, usually when threatened with cavalry attack. To deploy its weapons effectively, a traditional infantry unit would generally form a line; but the line was vulnerable to more nimble cavalry, which could sweep around the end of the line, or burst through it, and then attack the undefended rear or simply sweep along the line attacking the individual footsoldiers successively.