However, during World War II Canada's military contribution was to increase to the scale of a five-division, two-corps army and the formation was eventually redesignated as I Canadian Corps on April 6, 1942.

[1] The 1st Canadian Infantry Division had already been sent across the Atlantic between December 1939 and early 1940, and had been attached to VII Corps to help defend southern England against the threat of German invasion from occupied France.

As a result, the formation of a separate Canadian Corps was deemed advisable to accommodate and clearly highlight the growing military contribution from Canada.

From November–December 1941 Major General George Pearkes was asked to assume command of the Canadian Corps, taking the place of Andrew McNaughton who was on an extended leave.

Lieutenant-General Harry Crerar assumed command from December 23, 1941, to April 6, 1942.