The Lancashire Militia, based in Lancashire, England, was one of a number of county-based irregular military units designed to provide, during times of international tension, homeland security, relief of regular troops from routine garrison duties, and a source of trained officers and men for the regular Army.
The Lancashire Militia was formed when King William III ordered the Earl of Derby, then the Lord Lieutenant of Lancashire, to assemble and train the Militia as required under Charles II’s Act of 1662. After training on Fulwood Moor near Preston, the Militia embarked in 1690 for Ireland, where they fought at the Battle of the Boyne and the sieges of Carrickfergus and Athlone.
The Militia was again called upon, this time under the command of Sir Henry Houghton, to help suppress the Jacobite rising of 1715. They took part in the Battle of Preston on 12 November where they suffered heavy losses (11 officers and 105 men) attacking the rebel barricades in Church Street. They were again 'embodied' (called up) during the Jacobite rising of 1745 when the Young Pretender marched through Lancashire.
During the Seven Years' War (1754–63), when the Regular Army was fighting in Europe and there was a risk of French invasion, the Militia were reorganised under the Militia Act of 1757. From this date, proper uniforms and better weapons were provided, and the force was embodied from time to time for training sessions. Better records were kept and the men were selected by ballot to serve for longer periods. The existing Lancashire Militia was disembodied (broken up) in January 1746 and then re-raised in 1759, becoming the Royal Regiment of Lancashire Militia in 1761.
War with Revolutionary France in 1793 brought about an increase in the national strength of the Militia to 105,000 men. The Lancashire Militia was re-organised into three regiments, which provided a supply of trained officers and men for the Regular Army throughout the subsequent Napoleonic Wars of 1803–15. After the war the regiments were disembodied, although the 3rd Regiment, which had volunteered to stay on in Ireland, was renamed the Royal Lancashire Militia (The Duke of Lancaster’s Own) in 1831.