D-Day is the term used to describe the Allied invasion of Normandy on June 6, 1944, during World War II. It was a pivotal moment in the war, marking the beginning of the liberation of Western Europe from Nazi control. The operation involved a massive coordinated assault by American, British, Canadian, and other Allied forces, landing on five beachheads—Utah, Omaha, Gold, Juno, and Sword. D-Day set the stage for the subsequent Battle of Normandy and ultimately contributed to the defeat of Nazi Germany. The successful invasion is commemorated annually for its significance in shaping modern history.