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 24th Regiment of Foot. The 2nd Battalion of the 24th Regiment of Foot was formed on 10 December 1756 and renumbered as the 69th Regiment of Foot on 21 April 1758. The regiment took part in the Raid on St Malo in June 1758 and then formed part of a force which successfully captured Belle Île in spring 1761. It embarked for the West Indies later that year and took part in the Invasion of Martinique in January 1762 before returning home in 1763. The regiment returned to the West Indies in November 1781 and took part in the Battle of Saint Kitts in January 1782 and, while serving as marines, in the Battle of the Saintes in April 1782. In August 1782 the regiment took a county title as the 69th (South Lincolnshire) Regiment of Foot. The regiment returned home in 1785.