Empire ship the Normandy invasion depended on the successful construction of the Mulberry ports. These were prefabricated ports, constructed at Southampton, Gosport, Portsmouth, Tilbury Docks, and even as far north as Birkenhead and Hartlepool. Two hundred tugs then took three months to tow the components of the harbours from where they were constructed to assembly areas on the South Coast. Between 7 June 1944 and the end of July, the tugs towed the materials across the channel to Normandy. Before D-Day, sixty old merchant ships and four old warships were selected as blockships, to be scuttled in a line to give protection
D-Day (military term) originally set for June 5, 1944, but bad weather and heavy seas caused U.S. Army General Dwight David Eisenhower to delay until June 6 and "that" date has been popularly referred to ever since by the short title "D-Day". Because of the connotation with the invasion of Normandy, planners of later military operations sometimes avoided the term to prevent confusion. For example, Douglas MacArthur's invasion of Leyte began on "A-Day", and the invasion of Okinawa began on "L-Day". The Allies' proposed invasions of Japan would have begun on "X-Day" (on Kyūshū, scheduled for November 1945) and "Y-Day" (on Honshū, scheduled