The Byzantine Emperor never again attained the splendour of the reign of Justinian, but throughout the first milennium it remained rich and powerful.
During the early Middle Ages, Constantinople was an oasis of learning, law, art and culture at a time when Europe was plunged into a dark age of ignorance and illiteracy.
Considering themselves to be the leaders of Christianity, the Byzantine rulers dispatched missionaries to spread their religion and culture among the Slavic nations, especially Russia.
During this period, Constantinople produced some capable emperors, in particular Heraclius (610 - 41), Basil the Macedonian (867 - 86), Leo the Wise (886 - 912) and Basil the Bulgar-Slayer (976 - 1025).
Between them these rulers contributed a number of buildings to the city and recaptured lost provinces.
Never without enemies greedy for a share of the prodigious riches that had been amassed in the city, Constantinople was besieged by Slavs, Arabs, Avars, Bulgars, Persians and Russians, all without success because of the protection of the land walls.
The surrounding seas, meanwhile, were under the control ofConstantinople's powerful navy. Its main ship was the dromon, an oared vessel which could ram another ship but above all deliver the dreaded "Greek fire", an early form of napalm.
In 1059 Constantine X, the first of the Dukas dynasty of emperors, ascended to the throne. The state over which the dynasty presided was a weakened one, divided between the over-privileged bureaucracy in the capital and the feudal landlords of the provinces.
At the same time increasing dependency on foreign mercenaries placed the empire's defence in the hands of its most aggressive neighbours. These included the Normans from southern Italy, the Venetians and Turkic nomads from the East.
The Byzantine imperial army was totally destroyed at the Battle of Manzikert (1071) and again, a century later, at the Battle of Myriocephalon (1176) by the Seljuk Turks from the east.
These losses effectively ended Byzantine rule of Anatolia, which had for so long been the backbone of the empire.
The remarkable Comnenus dynasty (1081 - 1185) ruled for a century after the Dukas emperors, between these two defeats. Their main achievement was to succeed in holding the rest of the empire together.