Genius Bonus: The film takes place in 1916, but it doesn't specifically spell that out. You have to be familiar with the Battle of Verdun and Fort Douaumont to catch that. That means that all the chatter about the war ending soon is just wishful thinking: they still have a couple years to go.
"Seinfeld" Is Unfunny: Practically every Hollywood film over the next few decades that tried to depict the non-combat side of war was influenced by this film. As mentioned on the main page, Casablanca borrowed the La Marseillaise/Die Wacht am Rhein scene (and also imported Marcel Dalio, who played Rosenthal), and most films about a POW Camp used it as a template. Even The Sound of Music took cues for its final scene from this film's final scene.