In 747 the Tang general Gao Xianzhi, who had successfully fought the Tibetan empire in the Pamir Mountains, established Tang control over the Gilgit region. In early 748 the Arab general Abu Muslim occupied Merv, the capital of Greater Khorasan, and went on to lead what has become known as the Abbasid revolution. In the year 750, Abu al-'Abbas al-Saffah (As-Saffah) was proclaimed the first Abbasid caliph in the great mosque of Kufa. The Umayyad Caliphate fell in 750 at the Battle of the Zab. Abu Muslim had raised an army that included Muslims and non-Muslims, which he dispatched westwards to take control over Ummayyad territory. The Tang general and the Abbasid general would eventually meet in 750 when the kings of the Silk Road towns Tashkent and Ferghana sought the support of their imperial overlords in a battle of dominance. Gao Xianzhi conquered the Abbasid controlled Tashkent after a siege. The Abbasid general Ziyad ibn Salih escaped from Tashkent to Samarkand were he gathered troops and marched eastwards to confront the Tang army. In Fergana the Tang general Gao Xianzhi raised an army by recruiting Karluk Turks.