Once the Allies agreed to launch an invasion, when would it occur?
A staggering amount of planning was needed. Approximately 156,000 men would eventually storm the beaches of Normandy. How would such a plan remain secret?
An enormous amount of resources - men and materiel - would be required. Who would supply them? And, significantly, who would be in charge of the entire operation?
During the "Trident Conference," held in Washington during May of 1943, the Allies agreed to launch the invasion one year later - in May of 1944. A meeting in Quebec the following month, referred to as the Quadrant Conference, reaffirmed that decision.
In November of that year, Joseph Stalin pushed for the appointment of a Supreme Commander who would head the operation.
Because so many American resources would be involved in the attack, Roosevelt and Churchill agreed the chief commander would be an American. Initially, they thought the main coordinator of the U.S. military efforts - Army Chief of Staff General George C. Marshall - would be the best choice.
Although the position was offered to him, Marshall told the President the selection decision should be the Commander-in-Chief's. Deciding to find someone else, FDR reportedly told Marshall:
I feel I could not sleep at night with you out of the country.
In December of 1943, the job went to General Dwight D. Eisenhower, then commander of Allied Forces in North Africa and the Mediterranean Sea.
As Supreme Allied Commander in Europe, Eisenhower was also commanding general of all U.S. forces in the European Theater of Operations. He was given responsibility for the "direction" of strategic air forces as well.