Al-Hajjaj managed the eastern expansion from Iraq. His lieutenant governor of Khurasan, Qutayba ibn Muslim, launched numerous campaigns against Transoxiana (Central Asia), which had been a largely impenetrable region for earlier Muslim armies, between 705 and 715. Despite the distance from the Arab garrison towns of Khurasan, the unfavorable terrain and climate and his enemies' numerical superiority, Qutayba, through his persistent raids, gained the surrender of Bukhara in 706–709, Khwarazm and Samarkand in 711–712 and Farghana in 713. He established Arab garrisons and tax administrations in Samarkand and Bukhara and demolished their Zoroastrian fire temples. Both cities developed as future centers of Islamic and Arabic learning. Umayyad suzerainty was secured over the rest of conquered Transoxiana through tributary alliances with local rulers, whose power remained intact. From 708/09, al-Hajjaj's nephew Muhammad ibn Qasim conquered Sind (northwestern South Asia). The massive war spoils netted by the conquests of Transoxiana, Sind and Hispania were comparable to the amounts accrued in the early Muslim conquests during the reign of Caliph Umar ibn al-Khattab ().