History of the East–West Schism
Disunion in the Roman Empire further contributed to disunion in the Church. The Emperor Diocletian famously divided the administration of the eastern and western portions of the Empire in the early 4th century, though subsequent leaders (including Constantine) aspired to and sometimes gained control of both regions. Theodosius the Great, who established Nicene Christianity as the official religion of the Roman Empire (see Edict of Thessalonica), was the last Emperor to rule over a united Roman Empire. Following his death in 395, the division into western and eastern halves, each for a few decades still under its own Emperor, was never reunited.
Western Roman Empire
The authority of Julius Nepos as Emperor was accepted not only by Odoacer in Italy, but by the Eastern Empire and Syagrius in Gaul (who had not recognized Romulus Augustulus). Nepos was murdered by his own soldiers in 480, a plot some attribute to Odoacer or the previous, deposed emperor Glycerius, and the Eastern Emperor Zeno chose not to appoint a new western emperor. Zeno, recognizing that no true Roman control remained over the territories legally governed by the Western court, instead chose to abolish the juridical division of the position of Emperor and declared himself the sole emperor of the Roman Empire. Zeno became the first sole Roman emperor since the division after Theodosius I, 85 years prior, and the position would never again be divided. As such, the (eastern) Roman emperors after 480 are the successors of the western ones, albeit only in a juridical sense. These emperors would continue to rule the Roman Empire until the Fall of Constantinople in 1453, nearly a thousand years later. As 480 marks the end of the juridical division of the empire into two separate imperial courts, some historians refer to the death of Nepos and abolition of the Western Empire by Zeno as the end of the Western Roman Empire.