Answer: Because it involved a massive number of people and weapons.
Explanation:
One of the largest and most massive military operations in history, which, as such, is one of the most complexes. The process involved about three million soldiers who were transported to Normandy. The operation involved a paratrooper, an attack from the sea.
The operation lasted two months, which required the Allied troops to break through the German ring. It ended with the release of Paris. It required a considerable number of military maneuvers. A large number of weapons and people are involved. Due to its massiveness, long duration, and all the tactical plans contained in this operation, it is one of the most sophisticated military operations ever.
