'Plough' was an Allied unrealised plan for a US and Canadian force, specially trained for winter and mountain warfare, to attack a hydro-electric target in German-held northern Norway or northern Italy, or an oilfield target in Romania (winter 1942/43).

The force envisaged for this operation was the 1^st Special Service Force, a joint US and Canadian special forces unit trained at Fort Harrison near Helena, Montana in the USA. The volunteers for this 1,600-man force were mostly enlisted men located by intra-service recruitment which stated that preference would be given to men with experience as lumberjacks, forest rangers, hunters, game wardens, etc.

The 1^st Special Service Force was activated on 20 July 1942 under the command of Lieutenant Colonel Robert T. Frederick. The men received intensive training in stealth tactics, hand-to-hand combat, the use of explosives, amphibious warfare, rock climbing, skiing and mountain warfare. From the outset, the force was armed with a variety of non-standard or limited issue weapons, such as the M41 Johnson light machine gun and the force’s own V-42 fighting knife derived from the Fairbairn-Sykes weapon of British commandos.

The 1^st Special Service Force was activated on the basis of three small regiments and a service battalion. Following its initial training period in Montana, the 1^st Special Service Force was relocated to Camp Bradford, Vermont, on 15 April 1943, and to Fort Ethan Allen, Vermont, on 23 May 1943. On 4 July 1943 the 1^st Special Service Force arrived in San Francisco and on 10 July sailed for the Aleutian islands group. On 15 August the 1^st Special Service Force was part of the 'Cottage' (i) landing force of the island of Kiska, but after it had been discovered that the Japanese had evacuated their garrison, it re-embarked and returned to Fort Ethan Allen, arriving on 9 September.

'Plough' was schemed as an airborne assault into Norway for the destruction of strategic targets such as hydro-electric power plants, but was then abandoned.

In October 1943 Lieutenant General Mark W. Clark’s US 5^th Army arranged for the movement of the 1^st Special Service Force to Italy, where the force demonstrated the value of its unique skills and training up to August 1944. The 1^st Special Service Force arrived in Naples on 19 November 1943 and, after service in this theatre was used in 'Dragoon' (i) before being disbanded on 5 December 1944 after gaining an enviable fighting record including not one failure to take an objective assigned to it.