June 1944 was a major turning point of World War II, particularly in Europe. Although the initiative had been seized from the Germans some months before, so far the western Allies had been unable to mass sufficient men and material to risk an attack in northern Europe.
By mid-1944 early mobilization of manpower and resources in America was beginning to pay off. Millions of American men had been trained, equipped, and welded into fighting and service units. American industrial production had reached its wartime peak late in 1943. While there were still critical shortages -- in landing craft, for instance -- production problems were largely solved, and the Battle of the Atlantic had been won. Ever increasing streams of supplies from the United States were reaching anti-Axis fighting forces throughout the world.
By the beginning of June 1944, the United States and Great Britain had accumulated in the British Isles the largest number of men and the greatest amount of materiel ever assembled to launch and sustain an amphibious attack.
Strategic bombing of Germany was reaching its peak. In May 1943, the Combined Chiefs of Staff had given high priority to a Combined Bomber Offensive to be waged by the Royal Air Force and the U.S. Army Air Forces. By late summer 1943, Allied bombers were conducting round-the-clock bombardment of German industry and communications. In general, British planes bombed by night and American planes bombed by day. Whereas an air raid by 200 planes had been considered large in June 1943, the average strike a year later was undertaken by 1,000 heavy bombers.
After considerable study strategists determined to make the cross-channel attack on the beaches of Normandy east of the Cherbourg Peninsula. Early objectives of the operation were the deep-water ports at Cherbourg and at Brest in Brittany.