AD 800-1250 Medieval Byzantium

Byzantium remained a great power after the emperor Leo III (reigned AD 717-741) drove back the last Arab siege of Constantinople in 717. It dominated south-eastern Europe and Asia Minor and was rich, well-organised and powerful. Its territories fluctuated as its rivals rose and fell, but so long as its heartlands in Thrace, Anatolia and the great city of Constantinople itself remained, it could always restore itself.

In the 11th century a succession of short-lasting and ineffectual emperors undermined the empire, while new enemies made progress against it. There was what turned out to be a final break between the eastern and western churches in the 1050s. Social changes had undermined the Byzantine army, based on the peasant-soldier, and oppressive taxation produced a Slav rebellion. Turkic tribes – Uzes and Pechenegs – threatened the Balkans and Thrace, the Normans ended Byzantine power in Italy, and the Seljuq Turks inflicted a major defeat in Anatolia, depriving the empire of vital lands.

In the late 11th and most of the 12th centuries the Comnenian dynasty achieved a significant restoration of Byzantine power. However in 1204 the empire was shattered by the Fourth Crusade, produced by a devastating combination of dynastic quarrels inside Constantinople, mistrust between Byzantine and Latin Christians and the ambitions of Venice.