This is sort of an Italian version of 'Casablanca' but without the happy ending. It is about the brutality of the German occupation and the heroism and sacrifice of the Italian resistance to it.
One thing that is so striking about the movie is the year it was made - 1946. The German occupation which changed Italy from a German ally to a subject territory took place in 1943. In that year the Americans and British were fighting their way across Sicily and then fighting their way up the boot of the Italian peninsula. Which means that the doubtless fictionalized events in the movie were not historical. They were fresh, still-bleeding, wounds of the year before or at most of the year before that.
A fine movie made, no doubt, by people who had just lived it.