Bulgarian nobles, Peter and Asen, led a rising which was to lead to the establishment of a virtually independent Bulgarian state with the tacit acceptance if not approval of Constantinople.
Why did the tried and tested methods of Byzantine diplomacy fail in the twelfth century? Perhaps primarily because they were traditional. Alliances with newcomers concerned not merely to bask in the political glow of Byzantine hegemony, but to claim power for themselves--such as the usurping Normans or the land-hungry Turks--were impossible. In any case, the newcomers were of a faith which made their incorporation into an orthodox 'commonwealth' inconceivable. They had, therefore, to be fought, and military victory against these 'barbarians' became the main measure of imperial success. After the crushing Byzantine defeat by the Turks at Myriocephalon ( 1176) this became ever more difficult and became a pretext for the dynastic rivalries between the members of the houses of Comnenus and Angelus which bedevilled Byzantium in the last thirty years of the twelfth century. Disunity in Constantinople was fed by growing military insecurity and the growing isolation of the empire from its old allies on the periphery. When, under Manuel I ( 1143-80), the empire turned to the west for friends, new dangers accompanied the treaties and marriage alliances. For the rivalries of the western Mediterranean cities--Genoa, Pisa, and Venice--and the ambitions of the German emperors were imported into Byzantium and Constantinople, once the nerve-centre of a confident and expansionist empire, became in 1204, the target of western territorial ambitions.
The tenth century also inaugurated a period of great change in the Islamic world. It saw the final disintegration of the Abbasid caliphate based on Baghdad and the evolution of a number of independent Muslim states whose unity was most strongly expressed not by loyalty to the caliph in Baghdad (since the Fatimids had set up a rival caliphate in Egypt) but by the common use of the Arabic language for governmental purposes and by such important rituals as the annual hajj or pilgrimage to Mecca. More distant Muslim provinces, such as Ifriqiya, had paid only a token tribute to Baghdad and by about
-172-