ruled by a separate emperor, the Tetrarchy. Confident that he fixed the disorders that were plaguing Rome, he abdicated along with his co-emperor, and the Tetrarchy soon collapsed. Order was eventually restored by Constantine the Great, who became the first emperor to convert to Christianity, and who established Constantinople as the new capital of the Eastern Empire. During the decades of the Constantinian and Valentinian dynasties, the empire was divided along an east–west axis, with dual power centres in Constantinople and Rome. The reign of Julian, who under the influence of his adviser Mardonius attempted to restore Classical Roman and Hellenistic religion, only briefly interrupted the succession of Christian emperors. Theodosius I, the last emperor to rule over both East and West, died in 395 AD after making Christianity the official religion of the empire. The Western Roman Empire began to disintegrate in the early 5th century as Germanic migrations and invasions overwhelmed the capacity of the empire to assimilate the migrants and fight off the invaders. The Romans were successful in fighting off all invaders, most famously Attila, although the empire had assimilated so many Germanic peoples of dubious loyalty to Rome that the empire started to dismember itself. Most chronologies place the end of the Western Roman Empire in 476, when Romulus Augustulus was forced to abdicate to the Germanic warlord Odoacer. By placing himself under the rule of the Eastern Emperor, rather than naming a puppet emperor of his own, Odoacer ended the Western Empire. He did this by declaring Zeno sole emperor, and placing himself as his nominal subordinate. In reality, Italy was now ruled by Odoacer alone. The Eastern Roman Empire, also called the Byzantine Empire by later historians, continued to exist until the reign of Constantine XI Palaiologos. The last Roman emperor died in battle on 29 May 1453 against Mehmed II "the Conqueror" and his Ottoman forces in the final stages of the siege of Constantinople. Mehmed II would himself also claim the title of caesar or Kayser-i Rum in an attempt to claim a connection to the Roman Empire. Geography and demography The Roman Empire was one of the largest in history, with contiguous territories throughout Europe, North Africa, and the Middle East. The Latin phrase imperium sine fine ("empire without end") expressed the ideology that neither time nor space limited the Empire. In Virgil's epic poem the Aeneid, limitless empire is