History of Europe
In 395 Theodosius I, who had made Christianity the official religion of the Roman Empire, would be the last emperor to preside over a united Roman Empire. The empire was split into two halves: the Western Roman Empire centred in Ravenna, and the Eastern Roman Empire (later to be referred to as the Byzantine Empire) centred in Constantinople. The Roman Empire was repeatedly attacked by Hunnic, Germanic, Slavic and other “barbarian” tribes (see: Migration Period), and in 476 finally the Western part fell to the Heruli chieftain Odoacer.
History of the Roman Empire
The transition from a single united empire to the later divided Western and Eastern empires was a gradual transformation. In July 285, Diocletian defeated rival Emperor Carinus and briefly became sole emperor of the Roman Empire. Diocletian's reign stabilized the empire and marked the end of the Crisis of the Third Century. Diocletian appointed a co-emperor in 286 and delegated further with two junior-emperors.