an Iranian nobleman and the kanarang of Tus. The Sasanian rebel Burzin Shah, of the Karen family, revolted against Ibn Amir, though the latter crushed the rebels in the Battle of Nishapur. The Rashidun troops marched towards Herat and seized the city, concluding another treaty with its governor. Umayyad era (661–750) After the invasion of Persia under Rashidun was completed in five years and almost all of the Persian territories came under Arab control, it also inevitable created new problems for the caliphate. Pockets of tribal resistance continued for centuries in the Afghan territories. During the 7th century, Arab armies made their way into the region of Afghanistan from Khorasan. A second problem was as a corollary to the Muslim conquest of Persia, the Muslims became neighbors of the city states of Transoxiana. Although Transoxiana was included in the loosely defined "Turkestan" region, only the ruling elite of Transoxiana was partially of Turkic origins whereas the local population was mostly a diverse mix of local Iranian populations. As the Arabs reached Transoxiana following the conquest of the Sassanid Persian Empire, local Iranian-Turkic and Arab armies clashed over the control of Transoxiana's Silk Road cities. In particular, the Turgesh under the leadership of Suluk, and Khazars under Barjik clashed with their Arab neighbours in order to control this economically important region. Two notable Umayyad generals, Qutayba ibn Muslim and Nasr ibn Sayyar, were instrumental in the eventual conquest. In July 738, at the age of 74, Nasr was appointed as governor of Khorasan. Despite his age, he was widely respected both for his military record, his knowledge of the affairs of Khorasan and his abilities as a statesman. Julius Wellhausen wrote of him that "His age did not affect the freshness of his mind, as is testified not only by his deeds, but also by the verses in which he gave expression to his feelings till the very end of his life". However, in the climate of the times, his nomination owed more to his appropriate tribal affiliation than his personal qualities. The problems of Transoxiana could be resolved, although the Umayyad was on decline and being replaced by the Abbasid. In 724, immediately after the rise of Hisham ibn Abd al-Malik (r. 724–743) to the throne, Asad's brother Khalid al-Qasri was appointed to the important post of governor of Iraq, with responsibility over the entire Islamic East, which he held