Infantry square

Historically an infantry square, also known as a hollow square, is a combat formation an infantry unit forms in close order usually when threatened with cavalry attack. With the development of modern firearms and the demise of cavalry this formation is now considered obsolete.

The formation was described by Plutarch and used by the Romans, and was developed from an earlier circular formation. In particular, a large infantry square was utilized by the Roman legions at the Battle of Carrhae against Parthia, whose armies contained a large proportion of cavalry. This is not to be confused with the testudo formation, which also resembled a square, but was used for protection against ranged weapons such as arrows.

The Han Empire's mounted infantry forces effectively utilized tactics involving highly mobile infantry square formations in conjunction with light cavalry in their many engagements against the primarily cavalry Xiongnu nomad armies in the 1st century AD. Infantry squares were used in the siege of the nomads' mountain settlements near the Gobi region, where Han forces repelled nomad lancer attacks.

The square was revived in the 14th century as the schiltron, and later appeared as the pike square or tercio, and was widely used in the French Revolutionary and Napoleonic Wars.

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 (approx. 500 to 1,000 men) was the smallest force 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 weakened by attacks. A square of 500 men in four ranks, such as those formed by Wellington's army at Waterloo, was a tight formation less than twenty metres in length upon any side.

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