Passage to Marseille (1944), directed by Michael Curtiz.
The movie has several aspects, none really outstanding and together kind of confusing. Mostly it is beating the drum for the Free French allies during WW2. It also wants to tell the history of several characters, particularly Jean Matrac (Humphrey Bogart), a French journalist imprisoned before the War for opposing appeasement of the Nazis. But it has a serious (if very earnest) tone and explores the dilemma of the French, divided and conflicted during the War in ways that the other allies were not.
It is structured oddly, as a series of nested flashbacks:
We start with a hidden airfield in England used by the Free French Air Squadron. The commander (Claude Rains) tells how he and some of the men came there.
Flash back to a tramp steamer during the early part of the war. They pick up some dying men in a canoe who have escaped from Devil's Island.
Flash back to the prison and we get the stories of the men and their escape.
Flash back to their leader and his wife before the war. This is Bogart the journalist.
After each segment they pop the stack and return to the prior level until we are back at the beginning/end again.
(An aside: Stanislaw Lem had a short story with this repeated stacking motif which ends before the levels are fully unwound, which is disorienting. Shakespeare did the same in one of his plays; I will leave which one as an exercise for the reader).
The production uses much model work. There is an exciting climax where the steamer is attacked by a bomber. Bogart scandalously machine-guns downed German fliers in the water.
In a romantic bit he drops messages to his wife when he flies over her village. The final scene is especially cloying.
In some ways it is a Casablanca (1942) reunion: Curtiz, Bogart, Rains, Lorre, Greenstreet. And another Max Steiner score.
Written by Nordhoff & Hall, more famous for Mutiny on the Bounty.