The region of Transoxiana had been conquered by the Arab Muslims under Qutayba ibn Muslim in 705–715, following the Muslim conquest of Persia and of Khurasan in the mid-7th century.[1] The loyalty of Transoxiana's native Iranian and Turkic populations to the Umayyad Caliphate remained questionable, however, and in 719 the various Transoxianian princes sent a petition to the Chinese court and their Türgesh vassals for military aid against the Caliphate's governors.[2] In response, from 720 on the Türgesh launched a series of attacks against the Muslims in Transoxiana, coupled with uprisings among the native Sogdians. The Umayyad governors initially managed to suppress the unrest, but control over the Ferghana Valley was lost and in 724 the Arabs suffered a major disaster (the "Day of Thirst") while trying to recapture it.[3][4] Half-hearted efforts by the Umayyad government to placate the local population and win their support were soon reversed, and heavy-handed Arab actions further alienated the local elites. Consequently, in 728 a large-scale Transoxianan uprising broke out with Türgesh aid, which led to the Caliphate losing most of Transoxiana except for the region around Samarkand.[5][6]