The Supreme Commander of the Western Allies was the American General, Dwight Eisenhower, however direct command of the forces to be deployed in Normandy fell to Field Marshal Montgomery. The invasion was given the codename "Operation Overlord", and D-Day was set for May 1944.
The original plan for a landing in Normandy, as outlined by Sir Frederick Morgan, was for three infantry divisions to be put ashore in the first twenty-four hours. Eisenhower and Montgomery agreed that this was an insufficient number across too narrow a front, and so to prevent the possibility of a German counterattack throwing the troops back into the English Channel before sufficient reinforcements could land, the invasion area was extended to accommodate five divisions across a forty mile stretch of the Normandy coast.
Montgomery's 21st Army Group consisted of the 1st US Army, under General Omar Bradley, and the 2nd British Army, commanded by General Miles Dempsey. There were five invasion beaches, the two western-most of which, codenamed Utah and Omaha, were assigned to the Americans, whilst the British and Canadians were to land at Gold, Juno, and Sword in the east.
At the fore of this invasion, landing by parachute and glider, six hours before the first Allied soldiers would begin to assault the beaches, were the elite Airborne troops. In the west, directly ahead of Utah beach, the US 82nd and 101st Airborne Divisions were to land on the Cotentin Peninsula, whilst in the extreme east of the invasion area, six miles south of Sword beach, was the British 6th Airborne Division. These formations were to attack, capture or destroy numerous objectives during the night, and by dawn be lying in wait with the opposing flanks of the invasion area secured against enemy interference. Their role was pivotal to the success of the landings, however their casualties were expected to be extraordinarily high, as many as seven in every ten men.
The Germans, lured on by heavy bombing raids and targeted leaks of false information, were still convinced that the landings would take place in the Pas-de-Calais, although they suspected that Normandy may be the target of a minor and short-lived diversionary landing. Even if they had paid equal attention to Normandy, the Germans could not have expected anything like the enormous force that was to be thrown against them. In the first forty-eight hours alone, General Eisenhower planned to land over one hundred and seventy-five thousand men on French soil, reinforced by three thousand artillery pieces, one thousand five hundred tanks, five thousand other tracked vehicles, and ten thousand six hundred support vehicles of every type. Lending their weight to this unprecedented invasion were thousands of aircraft and the largest naval armada that the world had ever seen.