The historical 'D-Day' is related with-

During World War II (1939 - 1945), the Battle of Normandy, which lasted from June 1944 to August 1944, resulted in the Allied liberation of Western Europe from Nazi Germany’s control.

Codenamed Operation Overlord, the battle began on June 6, 1944, also known as D - Day, when some 156,000 American, British and Canadian forces landed on five beaches along a 50 - mile stretch of the heavily fortified coast of France’s Normandy region.

The invasion was one of the largest amphibious military assaults in history and required extensive planning.