The term D-Day in general denotes the unnamed day on which a military offensive is to be launched. In particular, D-Day refers to June 6, 1944, the day on which the Allied forces invaded France during World War II, and to the following victory over Germany; in this connection D-Day stands for the greatest logistical achievement in military history as well.
One day after the originally scheduled date, the Allies landed around 155,000 troops in Normandy; 57,500 Americans on the Utah and Omaha beaches; 75,000 British and Canadian soldiers on the Gold, Juno, and Sword beaches; plus nearly 23,500 British and American airborne troops. The troops had been delivered to the landing zones by an armada of nearly 900 merchant vessels and over 4,000 landing ships and landing craft, which had been marshaled and escorted by more than 1,200 naval combat ships. Some 195,700 personnel were assigned to the operation. In the air, nearly 12,000 fighter, bomber, and transport aircraft supported the landings, against which the Luftwaffe (the German air force) was able to deploy fewer than 400 planes. On this day, the Allied pilots flew over 14,000 sorties, and only 127 aircraft were lost. In the airborne landings on the flanks of the Utah and Sword beaches, more than 3,000 aircraft and gliders of the U.S. Army Air Force (USAAF) and the Royal Air Force (RAF) were used on D-Day.
“D-Day.” Europe Since 1914: Encyclopedia of the Age of War and Reconstruction. Ed. John Merriman and Jay Winter. Vol. 2. Detroit: Charles Scribner’s Sons, 2006. 780-784. World History in Context. Web.