The Age of Alliance
At its zenith the Ancestor civilisation encountered a species or civilisation of warlike Others, the Scae, that was rapidly expanding from the Coreward Deeps of Urakaya. The Ancestors established a defensive alliance to monitor and eventually oppose the Scae.
The Great War was slow in coming and built to its apocalyptic climax over millennia. The period before the Fall was one of relative peace and prosperity for most of Known Space. This period is known today as the Age of Alliance and is widely regarded as the closest that the Urakayan Communion has been to unity in the recorded history of the engaged powers.