Name given to the Roman Empire of the East, which flourished from 395 to 1453, being founded upon the death of Theodosius by division of the Roman Empire between his two sons. In the 5th century the Nestorian heresy began to prevail in the East, and the empire was forced to pay tribute to Attila to escape invasion. Religious matters were of special importance in Byzantine history because of the politico-ecclesiastical powers of the rulers and the interest of all classes in questions of doctrine and usage. Political and ecclesiastical dissension caused by the introduction of the Monophysite heresy was increased by rivalry between the patriarchs of Alexandria and Constantinople, until in 1215 the latter was declared second to Rome in honor by Pope Innocent III. The most brilliant period of the empire began under Justinian I, famous for his code of laws. His general, Belisarius, defeated the Persians and made conquests in Africa and Italy, and in 538 Saint Sophia was erected. In 610 Heraclius overthrew the usurper Phocas and in 622 crushed the Persians, and during the 7th century Greek became the language of the empire. Under Constantine IV (668-685) the Saracens were forced to raise their, siege of Constantinople, Bulgaria became a separate kingdom (680), and orthodoxy was reestablished. Under Leo the Isaurian (717-741) the last attack of the Saracens was repelled, army and finances were reorganized, and a campaign inaugurated for the destruction of sacred images which caused internal strife for a century. His successor Constantine V continued his policy of iconoclasm and persecution of monks, and though image-worship was restored by Irene (797-802), the Iconoclasts finally prevailed. With restoration of image-worship by Theodora (842-856) ecclesiastical authority became entirely subject to the throne. Theodora’s brother Bardas deposed Ignatius from the Patriarchate of Constantinople and appointed the layman Photius whose defiance of Pope Nicholas I (867) brought about the Great Eastern Schism. Basil I the Macedonian (867-886) established a new dynasty, with a revival of literature, art, and commerce, had Justinian’s code revised, and issued new law books, notably the Prochiron and the Basilica. Basil II (976-1025) defeated the Bulgarians and Saracens, issued a “Novel” (supplementary decree) against great landed proprietors, regulations concerning church property and against public officials seizing crown lands, increased commerce, and brought the empire to the summit of power. Under Constantine IX (1042-1055) Michael Caerularius, Patriarch of Constantinople, attempted to create a patriarchate equal to Rome, and was condemned by Leo IX. With the burning of the Bull of condemnation in Saint Sophia, Constantinople separated from Rome. Upon the expiration of the Macedonian dynasty in 1057 the throne was seized by Isaac Comnenus who renounced claim to spiritual jurisdiction while Crerularius encroached on temporal power. His successor, Constantine X, diminished the military forces, causing the loss of Italy, Croatia, Dalmatia, and Asia Minor. With the coming of the Crusaders and establishment of a Latin empire in the 13th century, commercial prosperity declined, and under a succession of incompetent rulers Byzantium looked to the West for aid against the threatened invasions of the Turks. Reunion of the Eastern and Western Churches attempted in the Council of Lyons in 1274 and the Council of Florence in 1439, was rejected by the Greek people, and in 1453 Constantinople was subjugated by Mohammed II who brought the empire to an end.