Alexius I had seen the importance of Hungary, lying between the Western and Byzantine empires, a neighbor of the Venetians and the Serbs. More ominous still was the establishment of the Norman kingdom of Sicily under Roger II in 1130. But John II astutely allied himself with the Western emperor against it.
No such cooperation was possible with Conrad’s successor, Frederick I Barbarossa (after 1152). To Frederick the alliance between the Holy Roman Empire and what he called “the kingdom of the Greeks” was not one between equals. Manuel launched a vain invasion of the Norman kingdom on his own account in 1154, but it was too late for a revival of Byzantine imperialism in the West. It was hard for the Byzantines to accept the fact that their empire might soon become simply one among a number of Christian principalities.
In the Balkans and in the Latin East Manuel was more successful. His armies won back much of the northwest Balkans and almost conquered Hungary, reducing it to a client kingdom of Byzantium. The Serbs, too, under their leader Stefan Nemanja, were kept under control, while Manuel’s dramatic recovery of Antioch in 1159 caused the Crusaders to treat the Emperor with a new respect. But in Anatolia he overreached himself. To forestall the formation of a single Turkish sultanate, Manuel invaded the Seljuq territory of Rūm in 1176. His army was surrounded and annihilated at Myriocephalon. The battle marked the end of the Byzantine counteroffensive against the Turks begun by Alexius I. Its outcome delighted the Western emperor, Frederick I Barbarossa, who had supported the Seljuq sultan of Rūm against Manuel and who now openly threatened to take over the Byzantine Empire by force.
Manuel’s personal relationships with the Crusaders and with other Westerners remained cordial to the end. But his policies had antagonized the Holy Roman Empire, the papacy, the Normans, and, not least, the Venetians. His effort to revive Byzantine prestige in Italy and the Balkans and his treaties with Genoa (1169) and Pisa (1170) roused the suspicions of Venice, and in 1171, following an anti-Latin demonstration in Constantinople, all Venetians in the empire were arrested and their property was confiscated. The Venetians did not forget this episode. They, too, began to think in terms of putting Constantinople under Western control as the only means of securing their interest in Byzantine trade.
Manuel’s policies antagonized many of his own people as well. His favouritism to the Latins was unpopular, as was his lavish granting of estates in pronoia. A reaction set in shortly after his death in 1180, originated by his cousin Andronicus I Comnenus, who ascended to the throne after another anti-Latin riot in Constantinople. Andronicus murdered Manuel’s widow and son Alexius II. He posed as the champion of Byzantine patriotism and of the oppressed peasantry. But to enforce his reforms he behaved like a tyrant. By undermining the power of the aristocracy he weakened the empire’s defenses and undid much of Manuel’s work. The King of Hungary broke his treaty, and Stephen Nemanja of Serbia declared his independence from Byzantium and founded a new Serbian kingdom. Within the empire, too, disintegration proceeded. In 1185 Isaac Comnenus, governor of Cyprus, set himself up as independent ruler of the island. In the same year the Normans again invaded Greece and captured Thessalonica. The news prompted a counterrevolution in Constantinople, and Andronicus was murdered.
He was the last of the Comnenian family to wear the crown. His successor, Isaac II Angelus, was brought to power by the aristocracy. His reign, and, still more, that of his brother Alexius III, saw the collapse of what remained of the centralized machinery of Byzantine government and defense. Isaac tried at least to keep his foreign enemies in check.
The Normans were driven out of Greece in 1185. But in 1186 the Bulgars began a rebellion that was to lead to the formation of the Second Bulgarian Empire. Matters were not made easier by the arrival of the Third Crusade, provoked by the loss of Jerusalem to the Muslim leader Saladin in 1187.
One of its leaders was Frederick I Barbarossa, whose avowed intention was to conquer Constantinople. He died on his way to Syria. But Richard I the Lion-Heart of England appropriated Cyprus from Isaac Comnenus, and the island never again reverted to Byzantine rule.