This story blends fiction and real life (for its time) into a great film. The economy of the dialogue and scene editing, as well as the portrayals of its actors is superb. I can’t think of any other actors switching with that cast and making the film work as well.
All this, while WWII was underway and the outcome still up in the air. In retrospect, knowing what we know today, this is truly a remarkable piece of work. Casablanca got all the pieces right.