Khurasan, and the Iranian eastern half of the Caliphate in general, offered fertile ground for the Abbasids' missionary activities. Far from the Umayyad metropolitan province of Syria, Khurasan had a distinct identity. It was home to a large Arab settler community, which in turn had resulted in a large number of native converts, as well as intermarriage between Arabs and Iranians. As a frontier province exposed to constant warfare, the local Muslims were militarily experienced, and the common struggle had helped further unify the Arab and native Muslims of Khurasan, with a common dislike towards the centralizing tendencies of Damascus and the exactions of the Syrian governors. According to later accounts, already in 718/9 the Abbasids had dispatched twelve "naqāb" into the province, but modern scholars are sceptical of such claims, and it appears that only after the failure of the Revolt of Zayd ibn Ali in 740 did the Abbasid missionary movement begin to make headway in Khurasan. In 745, the Khurasani Qahtaba ibn Shabib al-Ta'i travelled west to swear allegiance to Ibrahim ibn Muhammad, and it was with him that Abu Muslim was sent east to assume control.