21st Army Group
The 21st Army Group was the senior British formation in Northwest Europe in 1944-45. All ground forces landing on D-Day in Normandy on 6 June 1944 were under the command of 21st Army Group.
Senior Allied Formations in Northwest Europe
Supreme Headquarters Allied Expeditionary
Twenty-First Army Group, like all army groups, was composed of General Headquarters (GHQ) Troops, its component Armies, Lines of Communication (LofC) Troops, and base installations. After the German surrender, 21st Army Group was converted into the headquarters for the British zone of occupation in West Germany, being redesignated the British Army of the Rhine on 25 August 1945.
The 21st Army Group did not have a fixed
composition. Initially it included the British 2nd Army and the United
States 1st Army. The 1st Canadian Army came under command in Normandy while
1st U.S. Army reverted to U.S. control when their own army group
headquarters was formed
Britain formed seven armies in all theatres during the war, only one operated in Northwest Europe. (The others were the 1st, 8th, 9th, 10th, 12th and 14th, which served respectively in North Africa, the Mediterranean, Middle East, Iraq, Burma, and the Far East). Like army groups, armies did not have fixed compositions and were composed of two or more corps, plus “army troops” such as artillery and engineer assets. A corps was likewise a grouping of divisions, as well as “corps troops”. Army and corps troops could also include infantry and armoured brigades independent of divisional attachments.
Additionally, other elements variously came under direct command, including units of the 1st Allied Airborne Army during Operation MARKET-GARDEN for example, or the units besieging the German coastal garrisons after the front passed into Belgium.