After the German Army invaded the Soviet Union in June 1941, the Soviet leader Joseph Stalin began pressing his new allies for the creation of a second front in western Europe.
In late May 1942 the Soviet Union and the United States made a joint announcement that a "... full understanding was reached with regard to the urgent tasks of creating a second front in Europe in 1942."
However, British Prime Minister Winston Churchill persuaded US President Franklin D. Roosevelt to postpone the promised invasion as, even with US help, the Allies did not have adequate forces for such an activity.

Instead of an immediate return to France, the western Allies staged offensives in the Mediterranean Theatre of Operations, where British troops were already stationed.
By mid-1943 the campaign in North Africa had been won.
The Allies then launched the invasion of Sicily in July 1943, and subsequently invaded the Italian mainland in September the same year.
By then, Soviet forces were on the offensive and had won a major victory at the Battle of Stalingrad.
The decision to undertake a cross-channel invasion within the next year was taken at the Trident Conference in Washington in May 1943.
Initial planning was constrained by the number of available landing craft, most of which were already committed in the Mediterranean and Pacific.
At the Tehran Conference in November 1943, Roosevelt and Churchill promised Stalin that they would open the long-delayed second front in May 1944.

The Allies considered four sites for the landings: Brittany, the Cotentin Peninsula, Normandy, and the Pas-de-Calais.
As Brittany and Cotentin are peninsulas, it would have been possible for the Germans to cut off the Allied advance at a relatively narrow isthmus, so these sites were rejected.
With the Pas-de-Calais being the closest point in continental Europe to Britain, the Germans considered it to be the most likely initial landing zone, so it was the most heavily fortified region.
But it offered few opportunities for expansion, as the area is bounded by numerous rivers and canals, whereas landings on a broad front in Normandy would permit simultaneous threats against the port of Cherbourg, coastal ports further west in Brittany, and an overland attack towards Paris and eventually into Germany.
Normandy was hence chosen as the landing site.
The most serious drawback of the Normandy coast—the lack of port facilities—would be overcome through the development of artificial Mulberry harbours.
A series of modified tanks, nicknamed Hobart's Funnies, dealt with specific requirements expected for the Normandy Campaign such as mine clearing, demolishing bunkers, and mobile bridging.

The Allies planned to launch the invasion on 1 May 1944.
The initial draft of the plan was accepted at the Quebec Conference in August 1943.
General Dwight D. Eisenhower was appointed commander of Supreme Headquarters Allied Expeditionary Force (SHAEF).
General Bernard Montgomery was named as commander of the 21st Army Group, which comprised all land forces involved in the invasion.
On 31 December 1943 Eisenhower and Montgomery first saw the plan, which proposed amphibious landings by three divisions with two more divisions in support.
The two generals immediately insisted that the scale of the initial invasion be expanded to five divisions, with airborne descents by three additional divisions, to allow operations on a wider front and to hasten the capture of Cherbourg.
The need to acquire or produce extra landing craft for the expanded operation meant that the invasion had to be delayed to June.
Eventually, thirty-nine Allied divisions would be committed to the Battle of Normandy: twenty-two US, twelve British, three Canadian, one Polish, and one French, totalling over a million troops all under overall British command.
After the German Army invaded the Soviet Union in June 1941, the Soviet leader Joseph Stalin began pressing his new allies for the creation of a second front in western Europe. In late May 1942 the Soviet Union and the United States made a joint announcement that a "... full understanding was reached with regard to the urgent tasks of creating a second front in Europe in 1942." However, British Prime Minister Winston Churchill persuaded US President Franklin D. Roosevelt to postpone the promised invasion as, even with US help, the Allies did not have adequate forces for such an activity.
Instead of an immediate return to France, the western Allies staged offensives in the Mediterranean Theatre of Operations, where British troops were already stationed. By mid-1943 the campaign in North Africa had been won. The Allies then launched the invasion of Sicily in July 1943, and subsequently invaded the Italian mainland in September the same year. By then, Soviet forces were on the offensive and had won a major victory at the Battle of Stalingrad. The decision to undertake a cross-channel invasion within the next year was taken at the Trident Conference in Washington in May 1943. Initial planning was constrained by the number of available landing craft, most of which were already committed in the Mediterranean and Pacific. At the Tehran Conference in November 1943, Roosevelt and Churchill promised Stalin that they would open the long-delayed second front in May 1944.
The Allies considered four sites for the landings: Brittany, the Cotentin Peninsula, Normandy, and the Pas-de-Calais. As Brittany and Cotentin are peninsulas, it would have been possible for the Germans to cut off the Allied advance at a relatively narrow isthmus, so these sites were rejected. With the Pas-de-Calais being the closest point in continental Europe to Britain, the Germans considered it to be the most likely initial landing zone, so it was the most heavily fortified region. But it offered few opportunities for expansion, as the area is bounded by numerous rivers and canals, whereas landings on a broad front in Normandy would permit simultaneous threats against the port of Cherbourg, coastal ports further west in Brittany, and an overland attack towards Paris and eventually into Germany. Normandy was hence chosen as the landing site. The most serious drawback of the Normandy coast—the lack of port facilities—would be overcome through the development of artificial Mulberry harbours. A series of modified tanks, nicknamed Hobart's Funnies, dealt with specific requirements expected for the Normandy Campaign such as mine clearing, demolishing bunkers, and mobile bridging.
The Allies planned to launch the invasion on 1 May 1944. The initial draft of the plan was accepted at the Quebec Conference in August 1943. General Dwight D. Eisenhower was appointed commander of Supreme Headquarters Allied Expeditionary Force (SHAEF). General Bernard Montgomery was named as commander of the 21st Army Group, which comprised all land forces involved in the invasion. On 31 December 1943 Eisenhower and Montgomery first saw the plan, which proposed amphibious landings by three divisions with two more divisions in support. The two generals immediately insisted that the scale of the initial invasion be expanded to five divisions, with airborne descents by three additional divisions, to allow operations on a wider front and to hasten the capture of Cherbourg. The need to acquire or produce extra landing craft for the expanded operation meant that the invasion had to be delayed to June. Eventually, thirty-nine Allied divisions would be committed to the Battle of Normandy: twenty-two US, twelve British, three Canadian, one Polish, and one French, totalling over a million troops all under overall British command.
Normandy landings