At the opening of the sixth century, large segments of the Roman Empire had fallen to barbarian warlords. The Churches of Rome and Constantinople were locked in a schism rooted in different attitudes towards the decrees and definitions of the Fourth Ecumenical council held at Chalcedon in 451. The emperor Justinian (527-565) dreamed of reunifying and restoring the Empire; but to accomplish this he needed a unified Church. Before Justinian ascended the throne the schism between Rome and Constantinople had been healed, largely due to Justinian's influence, but a significant segment of the Eastern population (dubbed monophysites) would not accept the union and the imperial church remained divided.