During the Napoleonic Wars, the British government raised regiments known as "fencibles" for home service. These temporary units were used to protect British interests wherever the units were raised, in Great Britain or North America, and were not to be deployed for overseas duty on foreign soil. In this regard, they were similar to the members recruited under Canada's National Resource Mobilization Act (NRMA) during the Second World War; these members served in uniform in Canada but were not meant to serve with Canadian forces overseas. Unlike those soldiers, however, the fencibles faced a clear and present danger during the turbulent age of Napoleonic warfare that engulfed Europe as the War of 1812 was waged on the battlefields and waterways of North America.

Beginning in 1803 in British North America, fencible regiments were raised in Newfoundland, New Brunswick and Upper and Lower Canada for defence anywhere on the continent. Despite the initiative, none of the fencible regiments ever recruited to full strength. Other fencibles had their origins in units originally raised on the British Isles, which also suffered from weak numbers. For instance, the Canadian Regiment of Fencible Infantry was originally raised in Scotland, but suffered from massive desertion when rumours spread that they might be posted to the malaria-rich East Indies, thus requiring a recruitment drive in Upper and Lower Canada. While Scottish named and led, the regiment was filled primarily with French Canadians.

Fencibles had similar structure on paper to that of other regiments, and held similar pay, but their uniforms were naturally different to separate them from other units. Each fencible unit had a differently coloured facing on the traditional British red coats to help distinguish them amid the chaotic battlefield filled with ear-piercing artillery fire and fog of gun smoke.

Fencibles in Action in the War of 1812

Most fencible units saw action in key battles of the War of 1812, either in part or whole. The Royal Newfoundland Fencibles served at the Battle of Mackinac and the engagements on Lake Huron. The New Brunswick Fencibles contributed their services to the Battle of Sackets Harbor. The Canadian Regiment Fencibles of Infantry saw many of its units serve in a series of battles, including Chateauguay, Lacolle Mills, and Crysler's Farm. Units of the Glengarry Light Infantry Fencibles also served in a series of battles, and the entire regiment served at Lundy's Lane. The tiny Michigan Fencibles, only forty-five souls strong, saw action as well.

All these fencible units were disbanded in 1816, or were reconfigured as part of the general armed forces of Great Britain. With some exceptions, given their ad hoc nature and poor fighting strength, the fencibles served well but were comparatively undistinguished as part of the British forces during the War of 1812.