The Emperor's Naked Army Marches On: Incredibly harrowing documentary about one man who sets out on a crusade to hold his former comrades-in-arms accountable for wartime atrocities. Not a "war movie" but an amazing film about the psychic aftermath of war.
Ogawa Productions' series on the Narita Airport Protests, start with Summer in Sanrizuka: Not about a traditional war, but about a protracted and violent protest-conflict fought by farmers and activists against the police trying to confiscate land to build an airport. However, it is essentially a war documentary in feel.
Army of Shadows: French resistance during WWII, made by one of the greatest French film noir directors Jean-Pierre Melville.
Maybe Catch 22 as well, although its been a while since I've seen it...