The Commandos were formed after the British Expeditionary Force was evacuated from Dunkirk in 1940. Prime Minister Winston Churchill called for a force to be assembled and equipped to inflict casualties on the Germans and bolster British morale. Churchill told the joint Chiefs of Staff to propose measures for an offensive against German-occupied Europe, and stated, "they must be prepared with specially trained troops of the hunter class who can develop a reign of terror down the enemy coast."
One staff officer, Lieutenant Colonel Dudley Clarke, had already submitted such a proposal to General Sir John Dill, the Chief of the Imperial General Staff. Dill, aware of Churchill's intentions, approved Clarke's proposal. Three weeks later the first commando raid took place. The raiders failed to gather any intelligence or damage any German equipment; their only success was in killing two German sentries.
In 1940 the call went out for volunteers from among the serving Army soldiers within certain formations still in Britain, and men of the disbanding Divisional Independent Companies originally raised from Territorial Army Divisions who had seen service in Norway.[nb 1] In November 1940 the new army units were organised into a Special Service Brigade under Brigadier J. C. Haydon, with four Special Service Battalions. By the autumn of 1940 more than 2,000 men had volunteered for commando training.
There were 19 British Army Commandos formed in the United Kingdom and the Middle East. The No. 10 (Inter-Allied) Commando was formed from volunteers from the occupied territories and enemy aliens. In February 1942 the Royal Marines were asked to organise commando units of their own; 6,000 men volunteered, forming nine commandos. In 1943 the Royal Naval Commandos and the Royal Air Force Commandos were formed from volunteers from the Royal Navy and the Royal Air Force.
Also in 1943, the commandos started to move away from smaller raiding operations. They were being formed into brigades of assault infantry to spearhead the future Allied landing operations. Of the remaining 20 Commandos, 17 were used in the formation of the four Special Service brigades. The three remaining units, No. 12, No. 14 and No. 62 Commandos, were left to carry out smaller-scale raids. A shortage of volunteers and the need to provide replacements for casualties forced the disbandment of these three commando units by the end of 1943. No. 10 (Inter-Allied) Commando was left for the task of small scale raiding. No. 10 was the largest commando and was formed from volunteers belonging to the occupied territories. It could now provide both parachute and canoe trained sub units.
The Commandos came under the operational control of the Combined Operations Headquarters. The man initially selected as the commander was Admiral of the Fleet Sir Roger Keyes, a veteran of the Gallipoli Campaign and the Zeebrugge Raid in World War I. Keyes resigned in October 1941 and was replaced by Admiral Louis Mountbatten. The final Commander of Combined Operations was Major General Robert Laycock, who took over from Mountbatten in October 1943.