The plan of raising a fencible corps in the Highlands was first proposed and carried into effect by William Pitt the Elder, in the year 1759. During the three preceding years, both the fleets and armies of Great Britain had suffered reverses, and it was thought that a "home guard" was necessary as a bulwark against invasion.

The Fencibles were British regiments raised in the United Kingdom, Isle of Man and in the colonies for defence against the threat of invasion during the Seven Years' War, the American War of Independence, the French Revolutionary Wars, the Napoleonic Wars and the War of 1812 in the late 18th and early 19th centuries. Usually temporary units, composed of local recruits and commanded by Regular Army officers, they were usually confined to garrison and patrol duties, freeing Regular Army units to perform offensive operations. Most fencible regiments had no liability for overseas service.