The Longest Day is filmed in black and white, adding, I think, to the authenticity. Remarkably, the many Germans actually speak their own language among themselves, instead of a heavily German-accented English. Curt Juergens gives an excellent performance as a German officer bitterly skeptical of the Fuehrer's leadership. His is the "good German" character popular in American movies around the time that West Germany was being integrated into NATO. The joshing Catholic padre, another stock figure in World War II films of the time, makes an appearance.
For me a spine-tingling scene shows another German officer patrolling the Normandy coast with his beautiful German Shepherd dog. He's passing his Zeiss binoculars (the best ever made) over the incoming waters of the English Channel when he stops and freezes. Then he starts screaming, Die Invasion! Es ist die Invasion! What he's seeing before him is the greatest assemblage of naval power in the history of the world. Of course, his superiors at headquarters don't believe his telephoned report until it's too late and the Allies—Yanks, Brits, Canadians, and Gaullist French—have consolidated their beachhead.