Army of Shadows (1970) on Netflix

France, 1942, under German occupation. Philippe Gerbier, a civil engineer, is a French Resistance commandant. Denounced by a French collaborator, he is interned in a concentration camp. He manages to escape, and rejoins his network in Marseille, where he has the traitor executed. This movie reveals rigorously and austerely what life was like in the French Resistance: the solitude and fear of its members; their relationships with one another; the constant threat of arrest by the Gestapo; the Resistance command structure and the way its orders were carried out. Head writer Joseph Kessel and co-writer/director Jean-Pierre Melville were both veterans of the "Shadow Army".