Day 121, May 27

American General Dwight D. Eisenhower served as Supreme Commander of the Allied Expeditionary Forces, while overall command of ground forces (21st Army Group) was given to General Bernard Montgomery.

The operation, planned by a team under Lieutenant-General Frederick Morgan was the largest amphibious invasion in world history and was executed by land, sea and air elements under direct British-American command with over 160,000  soldiers landing on 6 June 1944: 73,000 Americans, 61,715 British and 21,400 Canadians. 195,700 Allied naval and merchant navy personnel in over 5,000 ships were also involved.

The invasion required the transport of soldiers and supplies from the United Kingdom by aircraft and ships, the assault landings, air support, naval interdiction of the English Channel and naval fire-suppor. . The landings took place along a 50-mile stretch of the Normandy coast divided into five sectors: Utah, Omaha, Gold, Juno, and Sword.