The geo-political background of this marvellous film, a film which transcends its WW2 propaganda efforts, is still not known to many: after the fall of France in 1940, most of France (except Paris and North and the coastal regions) was, in fact, at least until 1942-43, run by a virtually independent pro-German French administration based in the spa town of Vichy. The overseas colonies of France, from Devil's Island to Indo-China, were ideologically split: some supported Vichy, some de Gaulle's London-based "government", others a mid-way position based around local high-ranking French commanders (French Morocco and Algeria, to name but two).
Casablanca, a port in Morocco, played a quasi-independent game, allied to Vichy but full of all sorts of people, including people in the administration and police, until the Americans and British invaded "by invitation" in 1943 (Operation Torch). This film is set somewhat beforehand, although actually made a little later.
Many propaganda points in the film will not be picked up on by most viewers, as in the scene where the obnoxious Deutsche Bank exec fails to gain entrance to Rick's casino room and storms off saying he will "report it to Der Angriff". how many know that to have been Goebbels' newspaper?
Whatever one's views about WW2, this film can be enjoyed for itself. It is, of course, a classic, a classic noir at that. Everyone should own this film.