In the mid-eighth century, Inner Asia was a three-layered space: the Tang Empire from the east, the Abbasid Caliphate from the west, and between them a shifting band of Turkic-Sogdian cities and nomadic confederations. The Tang emperor Xuanzong's commander, the Korean-born general Gao Xianzhi, had since 747 been leading campaigns through the Pamir passes to break Tibetan and Türgesh pressure. In 750 Gao had the ruler of Tashkent (Chach) executed under a treaty, prompting the region's peoples to call on the Abbasids for help.

The army the Abbasid governor Abu Muslim sent from Khurasan, under Ziyad ibn Salih, met Gao Xianzhi's Tang army on the banks of the Talas River in the first weeks of July 751. The size of each force is uncertain — Arab sources give inflated figures of up to a hundred thousand for the Chinese; Chinese sources put the Tang army around thirty thousand; modern estimates suggest each side was likely between ten and twenty thousand. After five days of fighting, the Karluk Turks on the flanks and rear of the Tang army switched to the Abbasid side, and the outcome was decided. Gao Xianzhi withdrew with a small remnant; thousands of Tang soldiers were captured.

The battle does not loom large in contemporary Chinese or Arab records; for both empires it was a distant frontier event. Its consequences, however, were lasting: a few years later the An Lushan Rebellion (755) forced the Tang army to abandon the west entirely, and the Abbasid eastern frontier settled somewhere between the Indus and the Aral. More striking is that later Muslim writers — al-Tha'alibi among them — say that shortly after Talas, paper-making began in Samarkand by the hand of Chinese prisoners of war. Modern historians treat the story with caution — paper was already known in some form across Inner Asia — but the archaeology confirms that in the second half of the eighth century paper workshops did indeed proliferate in Samarkand and Baghdad.

The outcome turned out to be a long technological transition for the Mediterranean world, from parchment and papyrus to paper. Paper mills were running in Baghdad and Cairo in the ninth century, in al-Andalus (at Xàtiva) in the tenth; in the twelfth century paper spread through Italy into Europe, and in the fifteenth century it would form the ground beneath the printing press. As the first link in that long chain, Talas shows how long a historical shadow a minor frontier battle can cast.