<Tr> <Td> b . </Td> <Td_colspan="2"> ^ Between 1204 and 1261 there was an interregnum when the Empire was divided into the Empire of Nicaea, the Empire of Trebizond and the Despotate of Epirus, which were all contenders for rule of the Empire . The Empire of Nicaea is considered the legitimate continuation of the Byzantine Empire because they managed to re-take Constantinople . </Td> </Tr> <Tr> <Td> c . </Td> <Td_colspan="2"> ^ See Population of the Byzantine Empire for more detailed figures taken provided by McEvedy and Jones, Atlas of World Population History, 1978, as well as Angeliki E. Laiou, The Economic History of Byzantium, 2002 . </Td> </Tr> <P> The Byzantine Empire, also referred to as the Eastern Roman Empire, was the continuation of the Roman Empire in the East during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern - day Istanbul, which had been founded as Byzantium). It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Turks in 1453 . During most of its existence, the empire was the most powerful economic, cultural, and military force in Europe . Both "Byzantine Empire" and "Eastern Roman Empire" are historiographical terms created after the end of the realm; its citizens continued to refer to their empire as the Roman Empire (Greek: Βασιλεία τῶν Ῥωμαίων, tr . Basileia tôn Rhōmaiōn; Latin: Imperium Romanum), or Romania (Ῥωμανία), and to themselves as "Romans ." </P> <P> Several signal events from the 4th to 6th centuries mark the period of transition during which the Roman Empire's Greek East and Latin West divided . Constantine I (r . 324--337) reorganised the empire, made Constantinople the new capital, and legalised Christianity . Under Theodosius I (r . 379--395), Christianity became the Empire's official state religion and other religious practices were proscribed . Finally, under the reign of Heraclius (r . 610--641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin . Thus, although the Roman state continued and Roman state traditions were maintained, modern historians distinguish Byzantium from ancient Rome insofar as it was centred on Constantinople, oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity . </P>

Which half of the former roman empire is known as the byzantine empire after the fall of rome