During World War II it was formed to control forces of the British Expeditionary Force, after the expansion of that force had rendered control by just two corps headquarters cumbersome. The Corps was withdrawn from France after the defeat of British forces by the Germans in May of 1940.
Certainly the British Army is unusual in being based on a regimental system, where soldiers tend to remain attached to the same unit throughout their service.
The defeat of the British in the American War of Independence was due to factors other than the battlefield performance of the army.
As a result, the British Army’s central contribution to the allied victory between 1915 and 1918 was made by a blend of Territorials, “Kitchener Army” volunteers, and conscripts.
He was to receive not merely the lieutenant-colonelcy of the corps, but in case of his death, his wife was to have a pension and his children a grant of lands in America.
The fencible corps were "a species of militia, raised for the defence of particular districts, from which several of them could not by the conditions of their enlistment, be detached." Grose, Military Antiquities, I, 164.