Boeldieu and Captain von Rauffenstein (played by the director Erich von Stroheim) recognize each other as members of an elite whose customs, tastes and family connections link them across national boundaries. The measure of Renoir's generous spirit is that Rauffenstein and Boeldieu are also spared caricature. Renoir would hardly have forced von Stroheim, a director he revered, to play a cartoonish Prussian villain, and the script, by Renoir and Charles Spaak, takes pains to emphasize the tragic aspect of Rauffenstein's situation. Once a dashing flyer, he has been terribly injured in a plane crash, and his physical agony amplifies his pessimism. He foresees a future with no place for him and Boeldieu, a new Europe that belongs to the Maréchals and Rosenthals. Boeldieu sees it coming too, and embraces it as a cause. This is partly patriotism, a devotion to the bonds of common nationality that link the prisoners in the French part of the prison. In addition to the worker and the Jew there is an intellectual - devoted to the Greek poet Pindar, who has never been properly translated - and a music-hall entertainer played by the great comic actor Julien Carette. In the midst of a catastrophic war, far from the nightmare of the trenches, the gas and what seemed like the collective suicide of a civilization, they live in a peaceful microcosm of Europe. Care packages arrive full of the tastes of home. (In one hilarious scene the prisoners gather in the Russian barracks, waiting to share the caviar and vodka that must be in a newly arrived crate. But the czar has sent his loyal soldiers books instead, inciting a comic riot.) Much time is spent planning and performing sketches and musical numbers, including a cross-dressed version of "It's a Long Way to Tipperary" by British soldiers that segues into a stirring, impromptu rendition of "La Marseillaise." It may not be an accident that that scene prefigures one of the most famous moments in "Casablanca." One of the singers in that film, Rick's erstwhile mistress, Yvonne, is played by Madeleine LeBeau, at the time married to Dalio, seen in the role of Emil the croupier. Small world! Which is, in its way, the films" common moral. "Casablanca" aimed partly to rally Americans to the cause of democratic Europe, a cause that animates the hopes of "Grand Illusion." The title, taken from a 1909 book by Norman Angell (later called "The Great Illusion"), refers to the fallacy that the divisions among nations are inevitable causes of war, an illusion that is large ("grand" in French) but not necessarily exalted or noble. But is it also, in retrospect, an illusion that those divisions can be permanently overcome, that decency and fellowship can take the place of combat? The long history of modern Europe - in particular of France and Germany, the focal points of Renoir's film and of the present real-life Continental drama - pivots between a dream of community and a nightmare of conflict. Renoir traces both possibilities to a common source in the realm of ordinary human feelings and aspirations. Which is why Roosevelt's advice is still worth heeding, for statesmen and citizens alike. Correction: May 15, 2012 An earlier version of this article incorrectly identified Erich von Stroheim as a German film director. He was born in Austria, and later came to America.