The German U-boats in the Atlantic were defeated and the allied armies in Mediterranean achieved increasing success, as did soviet forces on the east front. Thorough preparations began during 1943. A new planning staff was assembled, and General Eisenhower was appointed supreme commander of the operation. Normandy was chosen for the landing because it was in range of fighter aircraft based England and had open beaches that were not as well defended as those of the Pas de Calais. it also had a fairly large port ,and was opposite the main port of southern england.in a few months before D-day allied forces wrecked the railways and bridges of northern France and achieved the necessary weakening of German air force strength others were amphibious tanks and artificial harbours. As with planning came rehearsal, on April 28th 1944, eight ships full of us servicemen and equipment were making their way to Devon coast in the UK to take part in a mistake in a rehearsal for the D-Day landings. Unfortunately, a mistake in their paperwork meant the ships were using different radio frequencies, so when a group of German boats picked up on the heavy radio traffic, the slow-moving US landing ships and their lack of communication proved to be