“D-Day” means the day on which a military operation begins. The “D” does not really stand for anything. It is derived from the word "Day". The term "D-Day" has been used for many different military operations. but it is now generally only used to refer to the Allied landings in Normandy on 6 June 1944. D-Day in Normandy was originally intended to be on 5 June 1944, but at the last minute bad weather delayed it until the following day. The armed forces use codenames to refer to the planning and execution of specific military operations. Operation Overlord was the codename for the Allied invasion of north-west Europe. The assault phase of Operation Overlord was known as Operation Neptune. This operation involved 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. By this time, the Allies had established a firm foothold in Normandy. Operation Overlord also began on D-Day, and continued until Allied forces crossed the River Seine on 19 August 1944. The Battle of Normandy is the name given to the fighting in Normandy between D-Day and the end of August 1944.
The majority of troops who landed on the D-Day beaches were from the English-speaking western free nations, the United States, the United Kingdom and Canada. However, troops from many other countries participated in D-Day and the Battle of Normandy, including: Australia, Belgium, Czechoslovakia, France, Greece, the Netherlands, New Zealand, Norway and Poland.
On D-Day, the Allies landed around 156,000 troops in Normandy. The American forces landed numbered 73,000: 23,250 on Utah Beach, 34,250 on Omaha Beach, and 15,500 airborne troops. 11,590 aircraft were available to support the landings. On D-Day, Allied aircraft flew 14,674 sorties, and 127 were lost.
In the airborne landings on both flanks of the beaches, 2395 aircraft and 867 gliders of the RAF and USAAF were used on D-Day.
Operation Neptune involved a massive naval force, including 6939 vessels: 1213 naval combat ships, 4126 landing ships and landing craft, 736 ancillary craft and 864 merchant vessels. Some 195,700 personnel were assigned to Operation Neptune: 52,889 US, 112,824 British, and 4988 from other Allied countries.
By the end of 11 June (D + 5), 326,547 troops, 54,186 vehicles and 104,428 tons of supplies had been landed on the beaches.
As well as the troops who landed in Normandy on D-Day, and those in supporting roles at sea and in the air, millions more men and women in the Allied countries were involved in the preparations for D-Day. They played thousands of different roles, both in the armed forces and as civilians.
Over 425,000 Allied and German troops were killed, wounded or went missing during the Battle of Normandy. This figure includes over 209,000 Allied casualties, with nearly 37,000 dead amongst the ground forces and a further 16,714 deaths amongst the Allied air forces. Of the Allied casualties, 83,045 were from 21st Army Group (British, Canadian and Polish ground forces), 125,847 from the US ground forces. The losses of the German forces during the Battle of Normandy can only be estimated. Roughly 200,000 German troops were killed or wounded. The Allies also captured 200,000 prisoners of war (not included in the 425,000 total, above). During the fighting around the Falaise Pocket (August 1944) alone, the Germans suffered losses of around 90,000, including prisoners.
Today, twenty-seven war cemeteries hold the remains of over 110,000 dead from both sides: 77,866 German, 9386 American, 17,769 British, 5002 Canadian and 650 Poles.