With the rule of Zoë (1028–50) anarchy and decline set in. The Seljuk Turks increased their attacks, and with the defeat (1071) of Romanus IV at Manzikert most of Asia Minor was permanently lost. The Normans under Robert Guiscard and Bohemond I seized S Italy and attacked the Balkans. Venice ruled the Adriatic and challenged Byzantine commercial dominance in the East, and the Bulgars and Serbs reasserted their independence.
Alexius I (1081–1118) took advantage of the First Crusade (see Crusades) to recover some territory in Asia Minor and to restore Byzantine prestige, but his successors of the Comnenus dynasty were at best able to postpone the disintegration of the empire. After the death (1180) of Manuel I the Angelus dynasty unwittingly precipitated the cataclysm of the Fourth Crusade. In 1204 the Crusaders and the Venetians sacked Constantinople and set up a new empire (see Constantinople, Latin Empire of) in Thrace, Macedonia, and Greece. The remainder of the empire broke into independent states, notably the empires of Nicaea and of Trebizond and the despotate of Epirus.
In 1261 the Nicaean emperor Michael VIII conquered most of the tottering Latin empire and reestablished the Byzantine Empire under the Palaeologus family (1261–1453). The reconstructed empire was soon attacked from all sides, notably by Charles I of Naples, by Venice, by the Ottoman Turks, by the new kingdoms of Serbia and Bulgaria, and by Catalonian adventurers under Roger de Flor. At the same time, the empire began to break down from within—the capital was at odds with the provinces; ambitious magnates were greedy for land and privileges; religious orders fought each other vigorously; and church and state were rivals for power.
Eventually the Turks encircled the empire and reduced it to Constantinople and its environs. Manuel II and John VIII vainly asked the West for aid, and, in 1453, Constantinople fell to Sultan Muhammad II after a final desperate defense under Constantine XI. This is one of the dates conventionally accepted as the beginning of the modern age. The collapse of the empire opened the way for the vast expansion of the Ottoman Empire to Vienna itself and also enabled Ivan III of Russia, son-in-law of Constantine XI, to claim a theoretical succession to the imperial title.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.