Spread across a 50-mile stretch of coastline in Normandy, a total of 6,000 ships and landing craft were involved, ferrying soldiers to five beaches known by their codenames - Sword, Gold, Juno, Omaha and Utah.
D-Day had been planned for more than a year, and those who were to take part spent several months training.
The aim of the ambitious air and sea assault was to begin the liberation of Nazi-occupied Europe.
By the end of the first day alone, as many as 4,400 Allied troops had died, with thousands more wounded.
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