O'Brien, the author, states that a true war story will contain obscenity and evil. The treatment of the baby buffalo represents a combination of both. The baby buffalo is found in the mountains after Curt Lemon died from stepping on landmine while he was playing catch with Rat Kiley. The baby buffalo is then tortured by Kiley, as he shoots away pieces of the animal. Kiley has just experienced the great loss of his best friend and is completely distraught. Unable to deal with his friends sudden death, he reverts to an obscene and evil mistreatment of a living creature. The baby buffalo could represent a form of purity or innocence that is (literally) taken away piece by piece. The young men in the story have their innocence stripped from them.
O'Brien's writing also critiques the meaning of truth. He criticizes overly romanticized war stories. His brutal depiction of the slaughter of the baby buffalo is meant to make the reader sick to their stomach. O'Brien does his best to replicate the atrocity of war. However, he poignantly brings to light the ways in which a reader who has never been to war will never know war. As such, he questions what it means to write a true war story. At the end of the story, O'Brien alludes to the possibility that the baby buffalo never existed. It is possible that the baby buffalo was metaphorical. But it is more likely that the baby buffalo represented the most truthful version of war O'Brien could convey to his readerm regardless of whether or not it actually existed.