 After the empire became divided into its western and eastern parts the Emperors of the East ruled from Constantinople over the lands of the Middle East as far east as the Euphrates and over the Balkans.This empire was a Greek-speaking, Christian empire, and became known to historians as the Byzantine Empire (from the earlier name of its capital city).The Parthians ruled Persia parallel to the Han Dynasty and around this time the Roman Empire reached the peak of its power.