D-Day: The Normandy Landings, 1944

US National Archives film of the 6 June 1944 Allied landings in Normandy — the largest seaborne invasion in history and the opening of a second front against Nazi Germany.
In the early hours of 6 June 1944, roughly 156,000 Allied troops crossed the English Channel and stormed five beaches along the coast of Normandy, backed by thousands of ships and aircraft. Codenamed Operation Overlord, it was the largest amphibious assault ever mounted. This US National Archives film records the landings that opened a second front in Western Europe and began the campaign to liberate France and push toward Germany, at a cost of thousands of casualties on the first day alone.
Public domain — source (US National Archives (via YouTube)). Free to reuse under the stated licence.