The First Shadow War, was a massive galactic conflict which happened approximately 1000 years before the Third Age of Mankind. During this war, the Shadows were held in check only by the combined efforts of the First Ones and several of the Younger Races, the Minbari most notably. Ironically, the First Shadow War occurred nine thousand years after the Last Great War against the Shadows. It implies many prior, undocumented wars. While a tremendous conflict by the younger races' standards, it was relatively mild compared to the "great" wars that came before.