The Leatherneck.

A film about male bonding. At the end of WW I, two Americans befriend a simple minded German and win him over into becoming an American. All three are still peacetime officers in the US Marines when an unscrupulous character steals Boyd's girl and his two buddies go off to rescue her. When they don't come back, Boyd goes after them to rescue all. This is all done in flashback from a court martial trial for desertion.