You don't have to drag yourself all the way to the '70s to find a solid anti-war movie. One of the best actually dates back to the early days of sound, when World War I was still on people's minds. All Quiet on the Western Front is a masterpiece of the genre, alternating brilliant battle scenes with heartfelt moments of emotion, as one soldier learns firsthand about the horrors of war. He later preaches peace while everyone around him calls him a coward and a traitor. Heavy stuff, especially for 1930.