怛罗斯战役
In 751 the first Abbasid caliph As-Saffah had defeated the Chinese Tang dynasty in the Battle of Talas. Chinese sources record that Al-Mansur sent his diplomatic delegations regularly to China. Al-Mansur's delegations were known in China as "Khayi Tashi" ("Black Clothes"). In 756 Al-Mansur sent more than 22,000 Arab mercenaries to assist Emperor Xuanzong of Tang in the An Shi Rebellion. The Muslim population of Ningxia are considered descendants of the Arab soldiers who settled after Chang'an was recaptured.