In the pre-dawn hours of June 6, 1944, the long-awaited invasion of Northern Europe by Allied armed forces began with the landing of airborne troops in the Normandy region of France. They were followed by an air and sea bombardment and subsequent landings by seaborne troops on the Normandy seacoast. The German forces occupied what was known as the "Atlantic Wall" of fortified positions and pre-sighted artillery. The landings were the largest such single-day operation ever, landing some 160,000 men, of whom over 4,000 were killed.