Nearly 3 million men were involved in the Normandy invasion June 6, 1944. Later known as D-Day, the simultaneous landings on beachheads code-named Utah, Omaha, Gold, Juno and Sword by United States, British and Canadian forces was considered the single-most decisive event in the 20th century.
Planning the invasion took more than a year, with 5,000 large ships, 4,000 small landing craft and more than 11,000 aircraft involved. It was actually scheduled for June 5, but bad weather delayed the offensive.