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Commanded by General (later Field Marshal) Sir Bernard Montgomery, 21st Army Group initially controlled all ground forces in Operation Overlord (the United States First Army and British Second Army).
It also was used as a command post for Allied Forces Command (AFHQ) for Free French, British and United States ground forces in Algeria in February 1943, under the command of General Sir Harold R. L. G. Alexander to coordinate the actions of the United States First Army advancing from the west and the British Eighth Army, advancing from the east against the German Afrika Korps.