The First Canadian Army was an army of some 170 000 men organized in 2 corps (5 divisions and 2 armoured brigades) formed overseas in 1942 under Lieutenant-General A.G.L. McNaughton. McNaughton's aim was to keep the Canadian Army together to lead the cross-channel assault on northwest Europe; instead, the Canadian government dispatched I Canadian Corps from McNaughton's command to serve in the Italian campaign in 1943 so that Canadian troops could see action. Because the existence of an identifiably Canadian army was important at home, Allied formations were added to the First Canadian Army to keep it up to strength.

Accordingly, when the First Canadian Army (now commanded by Lieutenant-General H.D.G. Crerar) went into battle on the left flank in France, Belgium and Holland, clearing the Channel coast after the Normandy Invasion, it had more Allied than Canadian troops. The balance was redressed in March 1945 following the Rhineland campaign, when the Canadians in Italy rejoined First Canadian Army for the Liberation of Holland. See also Battle of Ortona; Second World War (WWII).