Deserters (1983)

Louis is a 27-year-old reservist and patriot, as is his childhood friend and longtime rival Bastien, who sees the war, like everything else, as an opportunity. One night, as their unit sleeps near the front, they're bombed. Louis and his comrades fall back in disarray and in the general panic lose their regiment. When they locate it again a few hours later, their general accuses them of desertion.