WWII Movie in Marseille (from 1943, 44 or 45)

Hello ! I try to find the title of a movie, probably British, but maybe American, filmed between 1943 and1945. Black & white movie. The story is about pilots shot down and helped, hidden by French Resistance in the city of Marseille. The movie takes place during a very special (real) event : Marseille Round-up (Rafle de Marseille), January 22 - 23 1943. During that round-up, part of the city is evacuated and destroyed by the German (and we see that in that movie). Thanks for your help.