The exact location of the battle has not been confirmed but is believed to be near Taraz and Talas on the border of present-day Kazakhstan and Kyrgyzstan. The Chinese name Daluosi (怛羅斯, Talas) was first seen in the account of Xuanzang. Du Huan located the city near the western drain of the Chui River.
Before the battle, there were other indirect encounters between some of the combatants, and the military might of China had been projected beyond the harsh continental climate and the dry desolate difficult terrain of the Tarim Basin, much of which consists of the Taklamakan Desert, as early as the Han Dynasty, when Emperor Wu of Han sent military expeditions to seize horses, which got as far as the Ferghana. Then, in 715, Alutar, the new king of Fergana Valley, was installed with the help of the Arabs of the Umayyad Caliphate. The deposed Ikhshid (the king of Fergana) fled to Kucha (seat of Anxi Protectorate), and sought Chinese intervention. The Chinese sent 10,000 troops under Zhang Xiaosong to Ferghana. He defeated the Arab puppet-ruler Alutar at Namangan and reinstalled Ikhshid. The inhabitants of three Sogdian cities were massacred as a result of the battle. The second encounter occurred in 717, when Arabs were guided by the Turgesh and besieged two cities in the area of Aksu. The commander of the Chinese Protectorate General to Pacify the West, Tang Jiahui, responded using two armies, one composed of Karluk mercenaries led by Ashina Xin (client qaghan of Onoq) and another composed of Tang regulars led by Jiahui himself.
In the year 750, Abu al-'Abbas al-Saffah (As-Saffah), the founder of the Abbasid Caliphate, launched a massive rebellion (known as the Abbasid Revolution) against the incumbent Umayyad Caliphate from the province of Khurasan. After his decisive victory at the Battle of the Zab and eliminating those of the Umayyad family who failed to escape to Al-Andalus, As-Saffah sent his forces to consolidate his caliphate, including Central Asia, where his forces confronted many regional powers, including those of China's Tang Dynasty.
The numeric quantities of the combatants involved in the Battle of Talas are not known with certainty; however, various estimates exist. The Abbasid army (200,000 Muslim troops according to Chinese estimates, though these numbers may be greatly exaggerated) which included contingents from their Tibetan ally met the combined army of 10,000 Tang Chinese and 20,000 Karluk mercenaries (Arab records put the Chinese forces at 100,000 which also may be greatly exaggerated).
In the month of July 751, the Abbasid forces joined in combat with the Tang Chinese force (the combined army of Tang Chinese and Karluk mercenaries) on the banks of the Talas river.
The Tang army was subjected to a devastating defeat. The Tang dynasty's defeat was due to the defection of Karluk mercenaries and the retreat of Ferghana allies who originally supported the Chinese. The Karluks forces composed two-thirds of the Tang army changed to the Abbasid side while the battle was ongoing so that Karluk troops attacked the Tang army from close quarters and the main Abbasid forces attacked from the front so that the Tang troops were unable to hold their positions. The commander of the Tang forces, Gao Xianzhi, recognized that defeat was imminent and managed to escape with some of his Tang regulars with the help of Li Siye. Out of an estimated 10,000 Tang troops, only 2000 managed to return from Talas to their territory in Central Asia. Despite losing the battle, Li did inflict heavy losses on the pursuing Arab army after being reproached by Duan Xiushi. After the battle, Gao was prepared to organize another Tang army against the Arabs when the devastating An Shi Rebellion broke out in 755. When the Tang capital was taken by rebels, all Chinese armies stationed in Central Asia were ordered back to China proper to crush the rebellion.
Shortly after the battle of Talas, the domestic rebellion of An Lushan (755–63) and subsequent warlordism gave the Arabs the opportunity to further expand into Central Asia as Tang influence in the region retreated. The local Tang tributaries then switched to the authority of the Abbasids, Tibetans, or Uighurs and the introduction of Islam was thus facilitated among the Turkic peoples.
It was the An Lushan Rebellion and not the defeat at Talas that ended the Tang Chinese presence in Central Asia and forced them to withdraw from Xinjiang—Talas was of no strategic importance, because the Arabs did not advance any further after the battle.
A small minority of Karluks converted to Islam after the battle. The majority of Karluks did not convert to Islam until the mid 10th century under Sultan Satuq Bughra Khan when they established the Kara-Khanid Khanate. This was long after the Tang dynasty was gone from Central Asia.
Abu al-'Abbas al-Saffah, whose forces were known to the Chinese as the Black Robed Ta-Shih, spent his wealth on warfare. He died in the year 752 AD. His brother who succeeded him as the second Abbasid Caliph Abu Jafar al-Mansur (r. 754–775 AD) (A-p’uch’a-fo) helped the Chinese Emperor Suzong of Tang after he appealed for help during the An-Shi Rebellion in regaining control of his capital Chang'an from the treacherous commander, An Lushan, or his successors in the abortive Yan Dynasty. Abu Jafar al-Mansur responded by sending 4,000 men who helped the Tang troops in recapturing the city and were well rewarded by the Chinese Emperor. After the rebellion was repressed they were allowed to settle down permanently in China which helped in founding of the earliest Muslim communities in China. Some of them married local Chinese people and their descendants became native-born Muslims who retained their religious tradition and unique way of life.
In 760, a large scale massacre of wealthy Arab and Persian merchants occurred in China during the Yangzhou massacre (760), at the hands of Chinese rebels led by Tian Shengong. In 879 during the Guangzhou massacre, 120,000 to 200,000 Arab Muslim, Persian Zoroastrian, Jewish, and Christian foreign merchants in Guangzhou were massacred by Chinese rebels under Huang Chao.
The culture of Central Asia, once a mixture of Persian, Indian, and Chinese influences, disappeared under the power struggles between the empires of the Arabs, Chinese, Turks, Tibetans, and Uyghurs. Islam grew as the dominant cultural force of Central Asia.
With the decline of Central Asian Buddhism, Chinese Buddhism was now cut off from Indian Buddhism and developed into an independent religion with distinct spiritual elements. Indigenous Buddhist traditions like Pure Land Buddhism and Zen emerged in China. China became the center of East Asian Buddhism, following the Chinese Buddhist canon, as Buddhism spread to Japan and Korea from China.
Among the earliest historians to proclaim the importance of this battle was the great Russian historian of Muslim Central Asia, Vasily Bartold, of 20th century according to whom, "The earlier Arab historians, occupied with the narrative of events then taking place in western Asia, do not mention this battle; but it is undoubtedly of great importance in the history of (Western) Turkestan as it determined the question which of the two civilizations, the Chinese or the Muslim, should predominate in the land (of Turkestan)."
The loss of 8,000 troops to the Tang empire can be compared to a troop strength of more than 500,000 before the Anshi rebellion. According to Bartold, for the history of the first three centuries of Islam, al-Tabari was the chief source (survived in Ibn al Athir's compilation), which was brought down to 915. (Unfortunately, this important work was only compiled and published by a group of Orientalists in 1901.) It is only in Athir that we find an accurate account of the conflict between the Arabs and the Chinese in 751. Neither Tabari nor the early historical works of the Arabs which have come down to us in general make any mention of this; however, Athir's statement is completely confirmed by the Chinese History of the Tang Dynasty. In all Arab sources, the events which occurred in the eastern part of the empire are often dealt with briefly. Another notable informant of the battle on the Muslim side was Al-Dhahabi (1274–1348).
The Battle of Talas did not mark the end of Buddhism or Chinese influence in the region. The Buddhist Kara-Khitan Khanate defeated the Muslim Seljuq Turks and the Muslim Kara-Khanid Turks at the Battle of Qatwan in 1141, conquering a large part of Central Asia from the Muslim Karluk Kara-Khanid Khanate in the 12th century. The Kara-Khitans also reintroduced the Chinese system of Imperial government, since China was still held in respect and esteem in the region among even the Muslim population, and the Kara-Khitans used Chinese as their main official language. The Kara-Khitan rulers were called "the Chinese" by the Muslims.
Professor Denis Sinor said that it was interference in the internal affairs of the Western Turkic Khaganate which ended Chinese supremacy in Central Asia, since the destruction of the Western Khaganate rid the Muslims of their greatest opponent, and it was not the Battle of Talas which ended the Chinese presence.
Later during the reign of Abbasid Caliph Harun al-Rashid, the Arabs terminated their alliance with the Tibetan Empire, and established an alliance with China after sending envoys to China in 789.
The Battle of Talas was a key event in the history of paper—the technological transmission of the paper-making process. After the battle of Talas, knowledgeable Chinese prisoners of war were ordered to produce paper in Samarkand, or so the story goes. In fact, high quality paper had been known—and made—in Central Asia for centuries; a letter on paper survives from the fourth century to a merchant in Samarkand. But the Islamic conquest of Central Asia in the late seventh and early eighth centuries opened up this knowledge for the first time to what became the Muslim world, and so by the year 794 AD, paper manufacturing could be found in Baghdad, modern-day Iraq. The technology of paper making was thus transmitted to and revolutionised the Islamic world, and later the European West. The paper production was a state secret, and only some places and Buddhist Monks knew the technology. Of course, the paper was transported many kilometers as a Chinese luxury product, and as it was traded, the finding of paper in several places is not proof of production, but of use.
Other than the transfer of paper, there is no evidence to support a geopolitical or demographic change resulting from this battle. In fact it seems that Tang influence over Central Asia even strengthened after 751 and that by 755, Tang power in Central Asia was at its zenith. Several of the factors after the battle had been taken note of prior to 751. Firstly, the Karluks never in any sense remained opposed to the Chinese after the battle. In 753, the Karluk Yabgu Dunpijia submitted under the column of Cheng Qianli and captured A-Busi, a betrayed Chinese mercenary of Tongluo (Tiele) chief (who had defected earlier in 743), and received his title in the court on 22 October. The Chinese Muslim historian Bai Shouyi wrote that furthermore, at the same time that Talas took place, the Tang also sent an army from Shibao city in Qinghai to Suyab and consolidated Chinese control over the Turgesh. Chinese expansion in Central Asia did not halt after the battle; the Chinese commander Feng Changqing, who took over the position from Gao Xianzhi through Wang Zhengjian, virtually swept across the Kashmir region and captured Gilgit shortly two years later. Even Tashkent reestablished its vassal status in 753, when the Tang bestowed a title to its ruler. The Chinese influence to the west of the Pamir Mountains certainly did not cease as the result of the battle; Central Asian states under Muslim control, such as Samarkand, continued to request aid from the Tang against the Arabs in spite of Talas and hence in 754, all nine kingdoms of Western Turkestan again sent petitions to the Tang to attack the Arabs and the Tang continued to turn down such requests as it did for decades. Ferghana, which participated in the battle earlier, in fact joined among the central Asian auxiliaries with the Chinese army under a summons and entered Gansu during An Lushan's revolt in 756. Bai also noted that neither did the relations between the Chinese and Arabs worsen, as the Abbasids, like their predecessors (since 652), continued to send embassies to China uninterruptedly after the battle. Such visits had overall resulted in 13 diplomatic gifts between 752 and 798. Not all Turkic tribes of the region converted to Islam after the battle either—the date of their mass-conversion to Islam was much later, in the 10th century under Musa.