Peace on Earth is a 1939(eve of WWII) Metro-Goldwyn-Mayer Christmas-themed cartoon short subject directed by Hugh Harman, about a post-apocalyptic world populated by animals after war has rendered humans extinct.
"Many people get really shocked after watching this. I know, it's awfully sad. But this is what war is about. When you hear that word on TV, this is what they're talking about. So let's take time to think about it. We cannot let it happen anymore."