On D-Day, 6 June 1944, Allied forces launched a combined naval, air and land assaults on Nazi occupied France.
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 across five assault beaches - Utah, Omaha, Gold, Juno and Sword - 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.
By the end of the day, the Allies had established a foothold along the coast and could begin their advance into France.
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 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.
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.
To learn more about D-Day please visit the Imperial War Museum website.
Photograph credits: Imperal War Museum