T he armed forces used codenames to refer to planning and execution of specific military operations to prepare for D-Day. Operation Overlord was the codename for the Allied invasion of northwest Europe. The assault phase of Operation Overlord was known as Operation Neptune. This operation, which began on June 6, 1944, and ended on June 30, 1944, involved landing troops
on beaches and all other associated supporting operations required to establish a beachhead in France. By June 30th, the Allies had established a firm foothold in Normandy — 850,279 men, 148,803 vehicles and 570,505 tons of supplies had been landed.