Topic: Military History
Operation Overlord was entrusted to the British 21st Army Group, General Bernard Law Montgomery commanding. For the invasion of Normandy and the battle of the bridgehead, this force would consist of two armies: US First Army on the right and British Second Army on the left. As the bridgehead expanded and more Allied divisions came ashore, two more armies would be activated: US Third Army and Canadian First Army. At that point, the two US armies would come under the command of US 12th Army Group, General Omar Bradley commanding. Montgomery’s 21st Army Group would retain command of British Second Army and assume command of the new Canadian army. The whole array would then come under the command of General Eisenhower’s Supreme Headquarters Allied Expeditionary Force, relocated from Britain to France.
Organizationally, the US and British armies stood in stark contrast to the defending German Army with its polyglot order of battle. Within each Allied Army, divisions of the same type were exactly alike (Canadian divisions were organized along British lines.) For example, every US Army infantry division consisted of three regiments, each with three infantry battalions, three field artillery (FA) battalions with a total of 36 105mm howitzers, one FA battalion with twelve 155mm howitzers, a mechanized cavalry reconnaissance troop, a combat engineer battalion and various support units. Equipment and weapons were standardized down to the level of the rifle squad. British infantry divisions were similarly organized: three brigades, each with three infantry battalions. US armored divisions were similarly standardized with three armored battalions totaling about 150 medium tanks and 60 light tanks, three armored infantry battalions, three armored field artillery battalions with a total of 54 105mm self-propelled howitzers, an armored cavalry reconnaissance squadron and various support units. Again, British armored divisions were broadly similar. In both armies the division was the largest unit with a fixed organization. Between two and four divisions constituted a corps, and three to six corps formed an army.
Both armies disposed of a large number of non-divisional combat units. Before the war the US Army had envisioned employing tank and tank destroyer (antitank) battalions in independent groups. By 1944, however, it had become clear that the group concept was flawed and most such battalions were attached directly to divisions. Non-divisional FA battalions were controlled by FA group headquarters, most of which were assigned to corps. Mechanized cavalry groups, consisting of two armored cavalry reconnaissance squadrons, were also corps-level assets. On the British side the picture was similar, though non-divisional tank battalions were grouped in independent brigades.
For the actual invasion, the assaulting divisions had a large number of supporting units attached to them, e.g. amphibious tank battalions, special combat engineer units, naval gunfire direction teams, etc. Most such units were detached again after the landing.
On D-Day itself, five Allied divisions would come ashore: From right to left US 4th Infantry Division (Utah Beach) US 1st and 29th Infantry Divisions (Omaha Beach), British 50th Infantry Division (Gold Beach), Canadian 3rd Infantry Division (Juno Beach) and British 3rd Infantry Division (Sword Beach). They would face elements of five German divisions: three static infantry divisions, one field infantry division and one panzer division. (For more information, see Dr. Leo Niehorster’s detailed German and Allied orders of battle for 6 June 1944.)
