During the third week of July, the Allied forces were realigned as the buildup in Normandy reached its final phase. The 1st Canadian Army, commanded by Lieutenant-General Harry Crerar, was activated. When Headquarters 1st Canadian Army became operational at noon 23 July, it commanded no Canadian troops, only Lieutenant-General J.T. Crocker's 1st British Corps, which was to remain under command until March 1945. Only on 31 July did 2nd Canadian Corps, commanded by Major-General Guy Simonds, come under command. It, in turn, now included 4th Canadian Armoured Division, recently arrived from England. Until 1st Canadian Corps was moved from Italy in 1945, Canadian troops in the 1st Canadian Army were often a minority. In early August, the 1st Polish Armoured Division, recently arrived from England, started a three-month tour under Canadian command. The 51st (Highland) Division and the 7th British Armoured Division are examples of famous British divisions with extensive service under the 1st Canadian Army (and not just as a part of 1 British Corps).
The 1st Canadian Army formed part of the 21st Army Group, commanded by British General Bernard Montgomery. Meanwhile, the U.S. 1st and 3rd armies were combined to form the U.S. 12th Army Group under the command of General Omar Bradley. The new commander of the U.S. 1st Army was Lieutenant- General Courtney Hodges.