Mark Twain's short story, "The War Prayer" , is arguably the greatest anti-war short story in the history of American literature. The story was written after the Spanish-American War (and the Phillipine-American War)--a time when massive overseas expansionism was becoming more and more common. However, it was not published until after World War II, well after Twain's death in 1910.
While the story has no real plot, I always reckoned it could make a good film.
Someone has finally tried.