The D-Day invasion, also known as Operation Overlord, was the Allied forces' massive military operation on June 6, 1944, aimed at liberating Western Europe from Nazi occupation during World War II. This monumental event marked the beginning of the end for Nazi Germany as it involved a large-scale amphibious assault on the beaches of Normandy, France, leading to a crucial turning point in the war. The success of D-Day established a foothold for Allied troops in Europe and paved the way for further advancements against German forces.