The Early Byzantine Historians

The Byzantine Empire (or Byzantium) was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centered on the capital of Constantinople. Known simply as the "Roman Empire" (Greek: Βασιλεία Ῥωμαίων, Basileia Rhōmaiōn;[2] Latin: Imperium Romanum) or Romania (Ῥωμανία) to its inhabitants and neighbours, it was the direct continuation of the Ancient Roman State and maintained Roman state traditions.[3] Byzantium is today distinguished from ancient Rome proper insofar as it was oriented towards Greek culture, characterised by Christianity rather than Roman polytheism and was predominantly Greek-speaking rather than Latin-speaking.[3]

As the distinction between Roman Empire and Byzantine Empire is largely a modern convention, it is not possible to assign a date of separation; however, important points are the Roman Empire's administrative division into western and eastern halves in 285 by Emperor Diocletian (r. 284–305),[4] and Emperor Constantine I's (r. 306–337) decision in 324 to transfer the capital from Nicomedia (in Asia Minor) to Byzantium on the Bosphorus, which became Constantinople, "City of Constantine" (alternatively "New Rome").[n 1] The Roman Empire was finally divided in 395 AD after the death of Emperor Theodosius I (r. 379–395), thus this date is also very important if the Byzantine Empire (or Eastern Roman Empire) is looked upon as completely separated from the West. The transition to Byzantine history proper finally begins during the reign of Emperor Heraclius (r. 610–641), since Heraclius effectively established a new state after reforming the army and administration by introducing themes and by changing the official language of the Empire from Latin to Greek.[6]

The Byzantine Empire existed for more than a thousand years from its genesis in the 4th century until its final conquest in 1453. During most of its existence, it remained one of the most powerful economic, cultural, and military forces in Europe, despite setbacks and territorial losses, especially during the Roman–Persian and Byzantine–Arab Wars. The Empire recovered during the Macedonian dynasty, rising again to become a preeminent power in the Eastern Mediterranean by the late 10th century, rivaling the Fatimid Caliphate.