The most obvious difference between the east and west was the barbarian settlement. The Eastern Empire faced serious attacks along the length of the Danubian frontier—Attila’s great empire had targeted this region repeatedly, inflicting considerable damage. He only turned against the west in the final years of his career. Hunnic power collapsed rapidly after his death, but his sons led several major raids into Roman territory. Some of the powers to emerge from the wreck of Attila’s empire, notably several groups of Ostrogoths on the Pannonian and Thracian frontiers, proved equally hostile. Later in the fifth and sixth centuries new groups such as the Bulgars, Slavs, and Avars would be drawn into contact with the Roman frontier and would prove equally warlike and aggressive. Some barbarian groups had been permitted to settle in imperial territory from 382 onwards. Of these, a portion had subsequently migrated again, invariably moving into the lands of the Western Empire. Inevitably, we hear much less about any group that remained peaceful. Unlike their western colleagues, the eastern emperors were not forced to accept the permanent occupation by barbarian groups of substantial parts of their provinces.

From Adrian Goldsworthy’s The Fall of the West: The Slow Death of the Roman Superpower, London: Weidenfeld and Nicolson, 2009, p. 382.