D-Day is a military term designating the start of a military operation. The term "D-Day" has been used for many different operations, but in modern history it refers to what happened on 6 June 1944 - the day on which the Battle of Normandy began.
On 6 June 1944, thousands of Allied troops landed on the beaches of Normandy, in northern France, at the start of the battle to liberate mainland Europe from Nazi occupation. A total 75,215 British and Canadian troops and 57,500 US troops were landed by sea on D-Day. Another 23,400 were landed by air. By the end of 11 June, 326,547 troops, 54,186 vehicles and 104,428 tons of supplies had been landed on the beaches.
According to the US National D-Day Memorial Foundation, 4,414 Allied soldiers died on D-Day and many more were wounded. The total German casualties on D-Day are not known, but are estimated as being between 4000 and 9000 men.
When the Battle of Normandy was over, more than 425,000 Allied and German troops had been killed, wounded or were missing in action. Allied casualties totaled around 209,000, including 37,000 dead from the ground forces and almost 17,000 from the airborne forces.
The armed forces use codenames to refer to the planning and execution of specific military operations. There were two codenames used on D-Day:
Operation Overlord - codename for the Allied invasion of north-west Europe. Operation Overlord began on D-Day, and continued until Allied forces crossed the River Seine on 19 August 1944.
Operation Neptune - codename for landing the troops on the beaches, and all other associated supporting operations required to establish a beachhead in France. Operation Neptune began on D-Day (6 June 1944) and ended on 30 June 1944.
The fighting at the Battle of Normandy took place between D-Day and the end of August 1944.