D-Day: The largest amphibious invasion in history, D-Day was an Allied operation that took place on June 6, 1944, where British, American, and Canadian forces landed on the beaches of Normandy to liberate Western Europe from German occupation.
Operation Overlord: This was the codename for the overall plan of the Allies to invade and liberate Western Europe from German control during World War II. It included D-Day as one of its major components.
Battle of Stalingrad: Although not an Allied operation per se, this pivotal battle between Germany and Soviet Union marked a turning point in World War II. The Soviet victory at Stalingrad weakened Germany's Eastern Front and set the stage for subsequent offensives by the Allies.