The Khazar Incursion North to the provinces of Armenia and Azerbaijan, in the mountains of Caucasia, there dwelt the Khazar tribes and the Turks. In 727 A.D. the Turks invaded Armenia and Mesopotamia, but were driven out. In 731 A.D. a large force of the Khazar again invaded the Muslim provinces. The Arab governor, Jarrah, was defeated and killed and the invaders reached as far as Mosul. But Hisham sent a new force under Said al-Harshi, who defeated the Khazars with terrible slaughter, captured large numbers of them and drove others across the borders. Hisham, however, did not value the service of his intrepid general, al-Harshi, recalled him and appointed his brother Moslamah as the governor of Armenia and Mesopotamia in 732 A.D. A year later, in 733 A.D.
Moslamah was succeeded in the governorship by Merwan, who was an equally great Umayyad general. He inflicted several defeats on the Khazars and other Caucasian tribes and conquered Georgia in these mountains. For more than ten years, till he himself became the Caliph, Marwan defended the northern frontiers of the empire with great courage and soldierly skill. He tried and perfected new methods of warfare which later enabled him to win the throne for himself.4
