The Babylon Project

The Last Great War was a massive galactic conflict which happened approximately 10,000 years before the Third Age of Mankind.

The conclusion of this war saw the migration of almost all First Ones beyond the Rim, excepting the Shadows and the Vorlons, who stayed behind to guide the growth of the Younger Races.[1] Since the Shadows and Vorlons favoured different ideologies, it was agreed that a policy of non-aggression should exist between them, and that the Younger Races should be free to favour either Shadow or Vorlon ideology as they pleased. This policy lasted until the Second Shadow War of 2261 A.D.[2]

A Great War would occur every few thousand years.