Arrival of new enemies

The new enemies that emerged in the 11th century, unlike the Arabs or the Bulgars, had no cause to respect that reputation. They appeared almost simultaneously on the northern, the eastern, and the western frontiers. It was nothing new for the Byzantines to have to fight on two fronts at once. But the task required a soldier on the throne. The Pechenegs, a Turkic tribe, had long been known as the northern neighbours of the Bulgars. Constantine VII had thought them to be valuable allies against the Bulgars, Magyars, and Russians. But after the conquest of Bulgaria, the Pechenegs began to raid across the Danube into what was then Byzantine territory. Constantine IX allowed them to settle south of the river, where their numbers and their ambitions increased. By the mid-11th century they were a constant menace to the peace in Thrace and Macedonia, and they encouraged the spirit of revolt among the Bogomil heretics in Bulgaria. It was left to Alexius I to avert a crisis by defeating the Pechenegs in battle in 1091.

The new arrivals on the eastern frontier were the Seljuq Turks, whose conquests were to change the whole shape of the Muslim and Byzantine worlds. In 1055, having conquered Persia, they entered Baghdad, and their prince assumed the title of sultan and protector of the 'Abbasid caliphate. Before long they asserted their authority to the borders of Fatimid Egypt and Byzantine Anatolia. They made their first explorations across the Byzantine frontier into Armenia in 1065 and, in 1067, as far west as Caesarea in central Anatolia. The raiders were inspired by the Muslim idea of holy war, and there was at first nothing systematic about their invasion. They found it surprisingly easy, however, to plunder the countryside and isolate the cities, owing to the long neglect of the eastern frontier defenses by the emperors in Constantinople. The emergency lent weight to the military aristocracy in Anatolia who, in 1068, finally secured the election of one of their own number, Romanus IV Diogenes, as emperor. Romanus assembled an army to deal with what he saw as a large-scale military operation. It was a sign of the times that his army was mainly composed of foreign mercenaries. In August 1071 it was defeated at Manzikert, near Lake Van in Armenia. Romanus was taken prisoner by the Seljuq sultan, Alp-Arslan. He was allowed to buy his freedom after signing a treaty, but the opposition in Constantinople refused to have him back as emperor and installed their own candidate, Michael VII. Romanus was treacherously blinded. The Seljuqs were thus justified in continuing their raids and were even encouraged to do so. Michael VII invited Alp-Arslan to help him against his rivals, Nicephorus Bryennius and Nicephorus Botaneiates, each of whom proclaimed himself emperor at Adrianople in 1077 and at Nicaea in 1078. In the four years of ensuing civil war there were no troops to defend the eastern frontier. By 1081 the Turks had reached Nicaea. The heart of the empire's military and economic strength, which the Arabs had never mastered, was now under Turkish rule.

The new enemies in the West were the Normans, who began their conquest of South Italy early in the 11th century. Basil II's project of recovering Sicily from the Arabs had been almost realized in 1042 by the one great general of the post-Macedonian era, George Maniaces, who was recalled by Constantine IX and killed as a pretender to the throne. The Normans thereafter made steady progress in Italy. Led by Robert Guiscard, they carried all before them; in April 1071, Bari, the last remaining Byzantine stronghold, fell after a three-year siege. Byzantine rule in Italy and the hope of a reconquest of Sicily were at an end.

The disasters at Manzikert and at Bari, in the same year 1071, at opposite extremes of the empire, graphically illustrate the decline of Byzantine power. The final loss of Italy seemed to underline the fact of the permanent division between the Greek East and the Latin West, which was now not only geographical and political but also increasingly cultural and ecclesiastical. In 1054 a state of schism had been declared between the churches of Rome and Constantinople. The political context of the event was the Norman invasion of Italy, which at the time was a matter of as much concern to the papacy as it was to Byzantium. But the event itself, the excommunication of the patriarch Michael Cerularius by Cardinal Humbert in Constantinople, symbolized an irreconcilable difference in ideology. The reform movement in the Roman Church had emphasized an ideal of the universal role of the papacy that was wholly incompatible with Byzantine tradition. Both sides also deliberately aggravated their differences by reviving all the disputed points of theology and ritual that had become battle cries during the Photian Schism in the 9th century. The schism of 1054 passed unnoticed by contemporary Byzantine historians; its significance as a turning point in East - West relations was fully realized only later.