selves posed a threat to the unity of the empire. Byzantium had defended herself in the 'dark ages' by withdrawing her populations within the walls of her cities or by resorting to defensive guerrilla warfare. Now that she turned to the offensive, new tactics and a new style of leadership were called for. The soldier-farmers (stratiōtai) settled on the land in the seventh century were now required to equip themselves as heavy cavalry--an expensive business. Their leaders now needed to be professional soldiers of high calibre and it is in the tenth century that we first hear of the great families such as those of Phocas, Argyrus, Doucas, and Comnenus (all of which provided emperors before 1100) whose members both held great estates in the provinces and followed careers as professional soldiers. Military success could lead to higher ambition; the celebrated general Nicephorus Phocas crowned his triumphs on the eastern frontier and on Crete with a coup d'état in 963 by which he gained the imperial power. It was a process frequently repeated in the eleventh century and a major source of instability in Byzantium, for where one provincial magnate could succeed, what could prevent another? When a strong, militaristic emperor such as Basil II ( 976-1025) ruled, the centrifugal tendencies of the 'powerful' of the provinces could be kept in check by firm political action such as the confiscation of the estates of 'overmighty subjects'. But as the families jockeyed for the imperial power in the eleventh century, central authority was increasingly challenged by provincial factions. By the time strong dynastic rule was again re-established in the reign of the Emperor Alexius Comnenus ( 1081-1118), political disunity in the empire had already had serious consequences.
The most serious of these was an inability to curb the growing incursions of Turkish nomads into Asia Minor--the heartland of the empire in terms of both manpower and food production. The first appearance of Turkish raiders in Armenia in 1016-17 was later described in apocalyptic terms by the historian Matthew of Edessa, writing at the end of the eleventh century. But the presence of the 'ferocious beasts covered in blood' went largely unnoticed by Byzantine commentators until
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