The first day of the Allied invasion of occupied Europe on Tuesday, June 6th 1944. D stands for the "day" of actual landing. Codenamed Neptune in Allied Operation Overlord, the Normandy landings were conducted in two phases: an airborne assault landing of 24,000 mostly British, American and Canadian and French airborne troops shortly after midnight, and an amphibious landing of Allied infantry and armoured divisions on the coast of France starting at 6:30 AM. D-Day was a major turning point of World War II that led to eventual victory of the Allied forces.