What does D-Day stand for?
Literally, the ‘D’ stands for day, as in the day of the invasion. The earliest known reference goes back to 1917, but early in the Second World War it was called ‘Dog-Day’ after the phonetic alphabet of the day. It was used during Operation WATCHTOWER, the US invasion of Guadalcanal in the South Pacific, for example. Later, it became simply known as ‘D-Day’ and was used for all major amphibious operations including north-west Africa, Sicily and southern Italy.
The term ‘H-Hour’ was also used – the time of the landings – which was 6.30am on the two western beaches (Utah and Omaha); an hour later at 7.30am a little further to the east for the British landings; and 7.45am for the Canadians at Juno. This was because the Allies wanted to land when the tide was out in order to both avoid the beach obstacles (the Germans assumed any invasion would be at high tide so the Allies had less beach to cross and so had placed them closer to the high tide line) and because they needed the beach at low tide to allow successive waves of troops and vehicles the space and time to unload.
What happened on D-Day?
The invasion was codenamed Operation OVERLORD and took place on Tuesday 6 June, having been delayed by 24 hours because of poor weather. American, British and Canadian troops were to be landed on five different beaches across the Normandy coastline: the Americans at Utah at the base of the Cotentin Peninsular and at Omaha at the western end of the northern Normandy coast; the British were to land at Gold Beach, east of Omaha; then the Canadians at Juno; and the British again at Sword, the easternmost invasion beach. Allied airborne troops would be dropped by parachute or glider and secure the flanks – the Americans in the west and the British and Canadians in the east.
American assault troops and equipment landing on Omaha beach on the northern coast of France on D-Day, 6 June 1944. (Photo by Fox Photos/Getty Images)
In all, some 7,000 vessels were used including 1,213 warships and 4,127 landing craft of various types and sizes. Some 23,000 airborne troops were dropped and 132,000 men landed on the beaches. They were also supported by a staggering 12,000 Allied aircraft. Contrary to popular myth, more British and Canadian troops were delivered to Normandy on D-Day, while two-thirds of the aircraft; more than three-quarters of the landing craft and 892 of the warships involved were British, not American. Not all D-Day objectives were achieved, but the airborne troops did secure the flanks as planned and landings were broadly very successful.
D-Day beach landings map. (Image by Paul Hewitt – Battlefield Design)
British troops on their way to Normandy to take part in the D-Day landings. (Photo by Keystone/Getty Images)
Why did D-Day happen?
Back in June 1940, the British had retreated back across the Channel and then France, Britain’s ally, had surrendered. Nazi Germany then occupied much of continental Europe and also Norway. Following the defeat of France in the third week of June 1940, Britain successfully withstood the threat of invasion by decisively defeating the Luftwaffe; without control of the skies over southern England, a German invasion was an impossibility. This consigned Germany to a long, drawn-out war it could ill afford and to invading the resource-rich Soviet Union far earlier than planned.
The United States had been gearing up for war since the fall of France and when Germany’s Axis partner, Japan, attacked the US naval base at Pearl Harbor in Hawaii [on 7 December 1941], America was finally drawn into the increasingly global conflict.
An explosion at the Naval Air Station, Ford Island, Pearl Harbor, during the Japanese attack on 7 December 1941. (Photo by Fox Photos/Getty Images)
In December 1941, British and American war leaders met and agreed that the defeat of Nazi Germany was their first priority and that the best way to achieve this was by an invasion of France, using Britain as a launch-pad. The build-up of US forces in Britain began in January 1942, but it soon became clear this new coalition of Britain and the United States was not ready to crack Nazi-occupied Europe any time soon. Instead, a joint invasion of north-west Africa, held by pro-Germany Vichy France, was launched first in November 1942. With the British Eighth Army attacking from Egypt and the Anglo-US First Army from Algeria, the German-Italian forces were caught in a pincer in Tunisia, which finally fell in May 1943.
With increasingly large Allied forces now in the Mediterranean and with Italy teetering, it made sense to follow up with an assault on Sicily in July 1943 – and after victory there, a further invasion of southern Italy that September. Vital airfields were captured in southern Italy, from which Allied strategic air forces (those independent of ground operations) could work in tandem with bomber forces operating from Britain – and so tighten the noose around the Third Reich. Gaining air superiority over all of Western Europe was a non-negotiable prerequisite for any invasion and not until the spring of 1944 had that condition been met. Finally, in early June 1944, the Allies had the weight of men and materiel as well as control of the skies with which to invade. The date was set as 5 June 1944, which was then pushed back a day due to poor weather, to Tuesday 6 June.
US troops in landing craft during the D-Day landings. (Photo by Keystone/Getty Images)
What was the goal of D-Day?
The immediate goal was to make sure the invasion was successful. The Allies had amassed vast forces, but despite the thousands of warships and landing craft, only a fraction of Allied strength could be initially transported across the Channel. Allied intelligence was superb and so long as the exact location and timing of the invasion remained secret to the Germans, the attackers would achieve tactical surprise when they began landing in Normandy. This proved the case but thereafter the race was on as to which side could build up a decisive weight of forces in Normandy first.
This was where Allied air power came in, because it was the bombers and fighter-bombers that were responsible for slowing German reinforcements to the front, both of infantry units, but particularly their panzer divisions – formations of motorised infantry, artillery and tanks – which were the best Nazi Germany had. By blowing up bridges, railways and roads and harrying anything that tried to move in daylight, they were able to greatly slow up German movement to Normandy and allow increasing numbers of Allied troops and materiel to cross the Channel.
Once a decisive materiel advantage had been achieved, then the outcome of the battle in Normandy – and ultimately all of France and Western Europe – would not be in doubt. By brilliantly coordinating their forces in the air, at sea, and on land, and by using the full weight of their industrial and technological superiority, the Allies not only secured a foothold on D-Day, they won the race to build up forces at the front. The result was overwhelming victory in Normandy 77 days later in August 1944 and a catastrophic defeat for Nazi Germany.
Bomber crews of the US Ninth Airforce leave their B26 Marauder aircraft after returning from a mission to support the D-Day landings in Normandy. (Photo by Fred Ramage/Keystone/Getty Images)
How many casualties were there?
The Allies had braced themselves for as many as 40,000 casualties on D-Day, but they were far fewer – around 10,000 all told. Even on the American-assaulted Omaha Beach, made famous by films such as The Longest Day  and Saving Private Ryan , the Allies lost only 842 dead. It was a lot, but not as bad as most people think today or was feared at the time. German casualty figures on D-Day are not at all precise, but estimates put them at a similar number.
A still from the 1998 film ‘Saving Private Ryan’ starring Tom Hanks (front-right). (Photo by Allstar Picture Library/Alamy Stock Photo)
Overall, however, the Normandy campaign was brutal and spectacularly violent. Including both sides as well as civilians – and some 15,000 French civilians were killed – the average daily casualty rate of each of the 77 days of the battle was 6,675: higher than the Somme, Passchendaele and Verdun in the First World War.
(Image by Paul Hewitt – Battlefield Design)
‘Big war’: the Allies’ winning strategy
Allied strategy was to use ‘steel not flesh’: they wanted to use their enormous global reach and access to resources to make the Allied war effort as mechanised and technologically advanced as possible and to use machines – steel – in order to keep the number of men at the coal-face of war as low as possible. This they achieved very well: in Normandy only 16 per cent of British troops were infantry and just 7 per cent in tanks – figures that were much the same for the Canadians and Americans too.
More than 40 per cent, however, were service troops [men supporting the front line – Royal Army Service Corps, Royal Army Medical Corps etc]; this was the long supply tail that was a benchmark of Allied strategy. They harnessed naval and air brilliantly with the troops on the ground, while in contrast, by 1944 Nazi Germany’s much-reduced navy and Luftwaffe were able to contribute to the battle hardly at all, suppressed by massive Allied superiority.
The Allies were fighting ‘big war’, whereas the Germans were forced to fight largely on land only. For too long, the narrative of D-Day and the battle for Normandy has focused on the fighting on land, whereas it needs to be understood in its wider context and from the perspective of the Allies’ broader strategy.
James Holland is an award-winning historian, writer and broadcaster and author of Normandy ‘44: D-Day and the Battle for France (Bantam Press, May 2019). He is a fellow of the Royal Historical Society and a research fellow at Swansea University, and he hosts a weekly podcast with Comedian Al Murray about the Second World War, ‘We Have Ways of Making You Talk’. You can follow James on Twitter @James1940.