Excerpts from Books and Wikipedia
"The Arab victory over the Chinese at the Battle of Talas in 751 established Islam as the dominant religion in central Asia. This precipitated the collapse of China's central Asian empire. . . . However, newly Islamized Arabs also had expansion plans of their own, and in 710 they captured the great caravan cities of Bokhara and Samarkand. In 750, A Chinese army under Gao Xianji captured Tashkent and executed its Turkish ruler. The ruler's son enlisted the aid of the Arabs in expelling the Chinese. In 751 a 40,000-strong Arab-Turk army advanced into Chinese territory and met Gao's army on the Talas River, in modern Kyrgyzstan. . . . Only a few thousand Chinese soldiers escaped. . . At this time the use of paper spread in the Islamic world, and then to Europe in the thirteenth century." [1001 Days] "The incident that led directly to the Battle of the Talas River concerned some petty central Asian kingdoms. The rulers of Ferghana and Tashkent were feuding, and the king of Ferghana sought assistance from the local Chinese official, Gao Hsien-chih. Tashkent, in turn, sought aid from the Abbasids, and both the Chinese and the Abbasids responded by dispatching armies."