The Untold Story of the Equestrian Civil War

Everypony hates war. This much is clear. For the past thousand years, peace has reigned in Equestria. Thanks to a clever combination of diplomacy and the threat of military action. But now, a new threat surfaces. A rift is forming, and civil war is brewing. I'm assuming that you know of the Mane Six and the events of Season 4. If not, SPOILERS!