At first I was just going to ask Rooster about this movie, but then thought everyone might enjoy it...
It is a depiction of the D-Day landings at Normandy, June 6, 1944, where it appears great care was taken for accuracy. Some of the actors actually participated in WWII; also, BOTH Allied and Axis consultants were brought in for the film, including the widow of the great German General Erwin Rommel.
I learned of this film because Marianne posted the Wikipedia link, in some research she did about the French actor Bourvil - who was one of the actors in THE LONGEST DAY. https://en.wikipedia.org/wiki/The_Longest_Day_(film)
And I notice John Wayne acted in this film, also! I keep a list of movies-to-watch, and I am interested to know if the film is indeed as true to life, as historically accurate, as it appears?