Not very good. Interesting the 'flashbacks' but not much else!
1. Phony French patriotism, almost laughable. Especially the French kid on the boat. Or the officer played by Claude Rains with his ridiculous "rendition" by reading the suppose letter. Rather laughable!
2. Not one of Bogart's best role. Killing unharmed Germans I can understand but remember, it is fictional. Just acting all these guys. And Lorre's worst role for one I can remember him in such great classics like the German "M", and "Mr Moto" roles.
3. France NEVER carried out massive air raids against Nazi Germany. Some French airmen did volunteer in the British RAF to firebomb Nazi Germany. Free French Air Force did carry out some raids in Northern Africa and Italy. And a few fighter planes flew over Nazi Germany in the last days of the war, but not much else.
4. I doubt a French officer will be trusting enough to give a key of his room to a man he has never seen before, unless he is some idiot. Better stay with "Casablanca" and "Flying Tigers" with John Wayne.]
5. "Devil's Island" was already being phase out, interrupted by World War II, by the time this movie was made. And its worse time was from 1850s to the 1920s. By the 1930s, many prisoners were freed and allow to own lands and make a living from it as a "humanitarian gesture".
6. Nazi Germany already had electronic radars for air defense by 1941.