Le Soldat Laforêt (1972)

When he gets separated from his unit, Laforet (Roger Van Hool) becomes a de facto deserter during 1939 fighting in the French provinces. Most of the story concerns his love affair with a local farmgirl, as he competes for her affection with a refugee from Spain. When he presses her to make a decision between them, the choice doesn't go in his favor. Soon after this he joins up with the Resistance movement.