In an operation codenamed Neptune, the Allied liberation of Western Europe began with a series of landings on 6 June 1944 - D-Day. The "D" stood for day and resulted from the practice of ordering events on operational planning timelines in which days prior to the first day of an operation were listed as "D minus", and days after as "D plus". Neptune was part of larger operation codenamed Overlord which entailed the capture of the Normandy region as a start point for a broad-front advance through north-western Europe towards Germany.
On D-Day 75,215 British and Canadian, and 57,500 United States troops were landed along the Normandy coast of France. 23,400 were paratroopers and the remainder were landed on five codenamed beaches - the Americans on Utah and Omaha, the British on Gold and Sword, and the Canadians on Juno. The success of the landings was ensured by meticulous planning that had begun in mid-1943. German attention was diverted from the intended landing beaches by a detailed and convincing deception plan, sea front defences were subdued by intensive naval fire, and the Allied airforces enjoyed air superiority over much of France, and almost total supremacy over the landing areas. Apart from at Omaha, where a German division had unexpectedly moved for training, the Allied landing forces had little difficulty establishing beachheads ashore, allowing the build-up of supplies and reinforcements for the coming campaign. The landings resulted in over 10,000 Allied casualties.
By the time Neptune was declared at an end on 30 June, 850,279 troops, 148,803 vehicles and 570,505 tons of supplies had been landed and the five separate beachheads linked. By this time, however, bad weather and increasingly well co-ordinated German resistance had sapped the momentum of the Allied drive inland, which had bogged down about thirty kilometres from the beacheads. Much hard fighting would ensue before the larger objectives of Overlord were attained.