L'Amour fugitif (1982)

Original title: L'amour fugitif

In this routine drama, two men (a crass Brit and a slow Frenchman) decide to evade the war in 1917, but their flight on a stolen boat goes awry and they end up on the coast of France, close to the fighting they wanted to leave behind. Once on shore, they make the acquaintance of a like-minded young widow who begins an affair with both men (she just wants to have a child by each) -- but their unusually idyllic existence is threatened with imminent tragedy as the French army advances ever closer.