So, it wasn't that war was unknown here, it just wasn't typically pony-on-pony violence. Trying to explain that humans would fight each other was hard enough. Explaining why got to be more difficult, especially when a lot of times a war was fought in response to the last war. To many of the ponies, it made humans seem insane. They really didn't get that there was a massive difference in theological, political and social ideologies that often separated one "tribe" of humans from another. Internal pony history had been peaceful since Celestia and Luna had arrived, well over a thousand years ago. 