During the same year, the powerful general Rustam Khan, refused to obey Safavid orders, and marched towards Isfahan to depose Abbas II. However, Saru Taqi managed to have him killed at Mashhad. In 1644, some Bakhtiari tribes rebelled against Abbas II. The rebellion, however, was quickly suppressed by Saru Taqi. Saru Taqi led a drive against corruption and, as a result, made many enemies. On 11 October 1645 he was assassinated by a group of army officers. Abbas II then appointed Khalifa Sultan as his grand vizier on October 14. Khalifa Sultan had at first declined the offer, but quickly alter accepted. His established bureaucratic proficiency and past knowledge were definitely the deciding factors in this reappointment, albeit it may be possible that Abbas II recalled him into service in part with the goal of compressing the discontent about the scarcity of the positions given to men of religion under his predecessor. Unlike his father, Abbas II took an active interest in government and military matters once he began to rule for himself (probably around age 15). In the summer of 1648, Abbas II, who sought to recapture Kandahar from the Mughal Empire, marched from Isfahan with an army of 40,000 men and after capturing Bost, he laid siege to Kandahar and captured it after a brief siege on 22 February 1649. Abbas II then appointed the Georgian "ghulam" ("military slave") Mihrab Khan as the governor of the city. The Mughals attempted to retake the city in 1651 but the arrival of winter forced them to suspend the siege. The Mughal ruler Shah Jahan then sent his son Aurangzeb with an army of 50,000 soldiers to recapture Kandahar. Although Aurangzeb defeated Abbas II outside the city, he was unable to take it. His artillery train proved not up to the task. Aurangzeb attempted to take the fortress city again in 1652. In the meantime, Abdul Aziz, the Uzbek ruler of Bukhara, had entered into an alliance with Abbas II, and in May 1652, he dispatched 10,000 troops to Kabul to harass the Mughal supply lines. Though not strong enough to lift the siege, the Uzbek threatened a Mughal convoy of 2,000 troops who were escorting one and a half million silver coins to the besieger's army at Kandahar. After two months of fighting Safavid resistance, along with the growing activities of the Uzbeks, Aurangzeb was forced to abandon the campaign.