 The formation of the regiment was prompted by the expansion of the army as a result of the commencement of the Seven Years' War.On 25 August 1756 it was ordered that a number of existing regiments should raise a second battalion; among those chosen was the 19th Regiment of Foot.The 2nd Battalion of the 19th Regiment of Foot was formed on 10 December 1756 and renumbered as the 66th Regiment of Foot on 21 April 1758.