As used in the Napoleonic Wars, the formation was constituted as a hollow square or sometimes a rectangle, with each side composed of two or more ranks of soldiers armed with single-shot muskets or rifles with fixed bayonets. Generally, a battalion, with about 500 to 1,000 men, was the smallest force that was used to form a square. The unit's colours and commander were positioned in the centre, along with a reserve force to reinforce any side of the square that was weakened by attacks. A square of 500 men in four ranks, such as those formed by Wellington's army at the Battle of Waterloo, was a tight formation less than 20 m long on any side.