Jules manages to woo Catherine with his naivety and freshness, persuading her to accept his proposal of marriage. Jim is happy for the both of them, although he sees that Catherine may be just too stubborn and tempestuous to settle down easily, and bids them farewell as they travel to Germany for the wedding. Unfortunately, World War I breaks out with Jules and Jim drafted into the opposing armies. Fighting on the French front their chief fear is that they could shoot each other although, thankfully, they both make it to the Armistice. Visiting post-war Germany, Jim writes newspaper articles on the shattered country and visits his old friends, now with a five year old daughter Sabine (Sabine Haudepin). It's as if nothing has changed, yet Jim immediately realises that the marriage is in jeopardy. Catherine has had several lovers, even leaving for months at a time, in her confused desires to behave with the freedom that a man has. Jules, with absolute devotion, disregards these dalliances, determined to stay with Catherine at all costs (even when she's engaged in an affair with Albert).
However, it's obvious that even this freedom is not enough to keep Catherine with Jules. Now he comes up with an audacious suggestion which is that he divorces her and Jim marries Catherine, so that she at least stays within their tight circle. Jules and Jim's relationship seems strong enough to withstand such an upheaval, even with the resultant jealousy that could occur. Catherine agrees, relishing a situation where she can walk away from or pick up with any man she chooses. Jim is still in love with his mistress Gilberte (Vanna Urbino) in Paris though, and returns to her when he visits on business. This is just the sort of behaviour which sends Catherine into violent mood-swings (she is happy to mess other people around but doesn't relish it when the situation is reversed). Jules understands that his love will never be reciprocated, but never becomes angry with Catherine or Jim - their relationship remains. The situation requires some resolution though, with all of these external lovers making things complicated.
A quite astonishing film, Truffaut has conceived a fragment of cinema which is wonderfully alluring and a joy to watch. Functioning on several levels, Jules et Jim can be treated as anything from a simple love story to an allegory on the fractured state of Europe between the World Wars. It's difficult to describe just why the film is so physically entrancing (which is a testament to its cinematic quality) but various notable aspects are the beautiful use of composition; the striking and harmonious score; the imaginative use of film with fractional freeze-frames and frame shrinking; the period feel which is both of the early decades of the 20th Century and timeless. The dialogue (that of the characters and of the voice-over) has a remarkably strange feel, constantly surprising us with its twists and turns, which tells us more about the characters than the words themselves. With the addition of excellent, natural and sympathetic acting from the three leads we are drawn into caring for their future, even for difficult, manipulative Catherine. A very classy flick which can only become better with repeated exposure.