On the outbreak of the Napoleonic Wars, a major expansion of the land forces was put in place to deter an invasion; on 25 December 1804, some four hundred men raised in Surrey were placed on the Army establishment as the 2nd Battalion, 56th Regiment, shortly thereafter expanded to 656 men. The existing battalion of the regiment was, accordingly, redesignated as the 1st Battalion, 56th Regiment. Noting the great success the two existing battalions had had with recruiting, a third was later authorised, and raised in 1813 at Horsham as the 3rd Battalion, 56th Regiment.