What was D-Day?

John Delaney: On D-day, 6 June 1944, the Allies launched the largest naval air and land operation in the history of warfare. Codenamed Operation Overlord it marked the beginning of a long and costly campaign to liberate Europe from Nazi domination. Early on the 6 June Allied airborne forces dropped behind the beaches to secure the flanks of the landing zones, then at 6:30 hours troops began landing on the five assault beaches Utah, Omaha, Gold, Juno and Sword.

By the end of the day the Allies had gained a firm foothold along the coast and were ready to begin their advance inland. Although limited planning for an invasion of Europe began soon after the invasion of Dunkirk in 1940, detailed preparations for Operation Overlord did not begin until late 1943. A command team led by the American General Dwight D Eisenhower, was formed in December 1943 to plan the naval air and land operation. As a crucial part of their preparations for D-day, the Allies developed deception and misdirection campaigns to draw German attention and military strength away from Normandy. This included fake radio traffic and decoy equipment, such as inflatable tanks and dummy landing craft, and even imaginary military forces and special agents. 

To build up resources for the invasion British factories increased production and in the first half of 1944 approximately 9 million tons of supplies and equipment crossed the Atlantic from North America to Britain. A substantial Canadian force had been assembling in Britain since December 1939 and over 1.4 million American servicemen had arrived during 1943 and 1944 to take part in the landings. By 1944 over 2 million troops from 12 countries were in Britain preparing for the invasion. On D-day Allied forces consisted primarily of American, British and Canadian troops but also included Australians, Belgians, Czechs, Dutch, French, Greeks, New Zealanders, Norwegians, Rhodesians and Poles. 

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 on the first day. Warships also carried out bombardments on German coastal defenses before and during the landings, and provided artillery support for the invading troops. HMS Belfast led bombardment force E, supporting the British and Canadian assaults on Juno and Gold beaches. She opened fire at 5:27 a.m. on 6 June 1944. 

D-day did not bring an end to the war in Europe but it did signify, from that moment forward, victory in Europe was in sight. By August 1944 the Germans were in full retreat from France. 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. Germany's defeat in the Battle of the Bulge and the resultant manpower shortages allowed the Allies to recommence their advance into Germany itself.

On 6 June 1944, Allied forces launched Operation Overlord and began the fight to liberate north-west Europe from German occupation. 

Hear IWM curator John Delaney explain how this complex land, sea and air operation was planned - and the significance of the Allied success. 

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