D-Day - 6 June 1944 - was the largest amphibious invasion in the history of warfare. The statistics of D-Day, codenamed Operation Overlord, are staggering. The Allies used over 5,000 ships and landing craft to land more than 150,000 troops on five beaches in Normandy. The landings marked the start of a long and costly campaign in north-west Europe, which ultimately convinced the German high command that defeat was inevitable.
Here are 10 things you need to know about D-Day:
On D-Day, 6 June 1944, Allied forces launched a combined naval, air and land assault on Nazi-occupied France. The 'D' in D-Day stands simply for 'day' and the term was used to describe the first day of any large military operation.
Early on 6 June, Allied airborne forces parachuted into drop zones across northern France. Ground troops then landed across five assault beaches - Utah, Omaha, Gold, Juno and Sword. By the end of the day, the Allies had established a foothold along the coast and could begin their advance into France.
The defeat of Germany was acknowledged as the western Allies’ principal war aim as early as December 1941. Opening a second front would relieve pressure on the Soviet Union in the east and the liberation of France would weaken Germany’s overall position in western Europe. The invasion, if successful, would drain German resources and block access to key military sites. Securing a bridgehead in Normandy would allow the Allies to establish a viable presence in northern Europe for the first time since the Allied evacuation from Dunkirk in 1940.
Lieutenant-General Frederick Morgan and his team of British, American and Canadian officers submitted plans for the invasion in July 1943. Although limited planning for an invasion of Europe began soon after the evacuation of Dunkirk in 1940, detailed preparations for Operation 'Overlord' did not begin until after the Tehran Conference in late 1943.
A command team led by American General Dwight D. Eisenhower was formed in December 1943 to plan the naval, air and land operations. Deception campaigns were developed to draw German attention - and strength - away from Normandy. To build up resources for the invasion, British factories increased production and in the first half of 1944 approximately 9 million tonnes of supplies and equipment crossed the Atlantic from North America to Britain. A substantial Canadian force had been building up in Britain since December 1939 and over 1.4 million American servicemen arrived during 1943 and 1944 to take part in the landings.
D-Day required unprecedented cooperation between international armed forces. The Supreme Headquarters Allied Expeditionary Force (SHAEF) was an international coalition and although the Allies were united against Germany, the military leadership responsible for 'Overlord' had to overcome political, cultural and personal tensions.
By 1944, over 2 million troops from over 12 countries were in Britain in preparation for the invasion. On D-Day, Allied forces consisted primarily of American, British and Canadian troops but also included Australian, Belgian, Czech, Dutch, French, Greek, New Zealand, Norwegian, Rhodesian and Polish naval, air or ground support.
The invasion was conducted in two main phases - an airborne assault and amphibious landings. Shortly after midnight on 6 June, over 18,000 Allied paratroopers were dropped into the invasion area to provide tactical support for infantry divisions on the beaches. Allied air forces flew over 14,000 sorties in support of the landings and, having secured air supremacy prior to the invasion, many of these flights were unchallenged by the Luftwaffe.
Nearly 7,000 naval vessels, including battleships, destroyers, minesweepers, escorts and assault craft took part in Operation 'Neptune', the naval component of 'Overlord'. Naval forces were responsible for escorting and landing over 132,000 ground troops on the beaches. They also carried out bombardments on German coastal defences before and during the landings and provided artillery support for the invading troops.
Germany tried to defend the northern coast of France with a series of fortifications known as the 'Atlantic Wall'. However, German defences were often incomplete and insufficiently manned.
Members of the French Resistance and the British Special Operations Executive (SOE) provided intelligence and helped weaken defences through sabotage. The Allied deception campaigns succeeded in convincing the Germans as late as July 1944 that the main invasion force would still land elsewhere. The threat of this larger, second invasion kept German reinforcements tied down away from Normandy.
Defence also suffered from the complex and often confused command structure of the German Army as well as the constant interference of Adolf Hitler in military matters. However, the Allies faced a number of setbacks both on 6 June and in the months that followed.
On D-Day, the Americans came close to defeat on Omaha partially because the preliminary air and naval bombardment failed to knock out strong defence points, but also because they faced highly effective German troops who had gained hard-earned experience on the Eastern Front. Throughout the Battle of Normandy, the technical superiority of their tanks and anti-tank weapons, as well as the tactical skill of their commanders, gave German forces an advantage over the Allies. However, the Germans were never able to fully exploit their successes or the weaknesses of the Allies in a decisive way.
D-Day was made possible because of Allied efforts across all fronts, both before and after June 1944. In planning D-Day, Allied commanders drew important lessons from previous failures at Dieppe in France and Anzio in Italy.
The Allied strategic bombing campaign, which began in 1942, weakened German industry and forced Germany to commit manpower and resources away from Normandy to home defence. Securing air superiority allowed the Allies to carry out aerial reconnaissance, giving them vital intelligence on German coastal defences.
D-Day also depended on Allied control of the Atlantic, which was finally achieved in 1943 through victory in the Battle of the Atlantic.
The campaign in Italy directed German troops away from the Western and Eastern Fronts. The Soviet Belorussian offensive, Operation 'Bagration', was launched just after 'Overlord' and destroyed the entire German Army Group Centre. It also kept German forces tied down in the east. Ten weeks after D-Day, the Allies launched a second invasion on the southern coast of France and began a simultaneous advance towards Germany.
The importance of D-Day often overshadows the overall significance of the entire Normandy campaign. Establishing a bridgehead was critical, but it was just the first step. In the three months after D-Day, the Allies launched a series of additional offensives to try and advance further inland. These operations varied in success and the Allies faced strong and determined German resistance.
The bocage - a peculiarity of the Normandy landscape characterised by sunken lanes bordered by high, thick hedgerows - was difficult to penetrate and placed the advantage with the German defenders. Yet the bloody and protracted Battle of Normandy was a decisive victory for the Allies and paved the way for the liberation of much of north-west Europe.
'Overlord' did not bring an end to the war in Europe, but it did begin the process through which victory was eventually achieved. By the end of August 1944, the German Army was in full retreat from France, but by September Allied momentum had slowed. The Germans were able to regroup and launched a failed but determined counter-offensive in the Ardennes in December 1944. This defeat sapped German manpower and resources and allowed the Allies to resume their advance towards Germany.
In this cartoon, one man says to the other: 'When they call us D-Day Dodgers, which D-Day do they mean, old man?' 'D-Day' is a general term for the start date of any military operation - the 'D' stands for 'day'. It is often used when the exact date is either secret or not yet known. Some people thought soldiers serving in Italy were avoiding 'real combat' in France and called them 'D-Day Dodgers'. But troops in Italy had faced their own D-Days at Sicily, Salerno, and Anzio and were engaged in a dangerous and difficult advance up the Italian peninsula.