After Manzikert, the dominion of Alp Arslan extended over much of western Asia. He soon prepared to march for the conquest of Turkestan, the original seat of his ancestors. With a powerful army he advanced to the banks of the Oxus. Before he could pass the river with safety, however, it was necessary to subdue certain fortresses, one of which was for several days vigorously defended by the Kurdish rebel, Yusuf al-Kharezmi or Yusuf al-Harani. Perhaps over-eager to press on against his Qarakhanid enemy, Alp Arslan gained the governor's submission by promising the rebel 'perpetual ownership of his lands'. When Yusuf al-Harani was brought before him, the Sultan ordered that he be shot, but before the archers could raise their bows Yusuf seized a knife and threw himself at Alp Arslan, striking three blows before being slain. Four days later on 24 November 1072, Alp Arslan died and was buried at Merv, having designated his 18-year-old son Malik Shah as his successor.[20]