were linked on the first day, and all five beachheads were not connected until 12 June; however, the operation gained a foothold that the Allies gradually expanded over the coming months. German casualties on D-Day have been estimated at 4,000 to 9,000 men. Allied casualties were documented for at least 10,000, with 4,414 confirmed dead. Museums, memorials, and war cemeteries in the area now host many visitors each year. Background 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 U.S. President Franklin D. Roosevelt to postpone the promised invasion as, even with U.S. 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