Tang campaigns against the Western Turks The Tang campaigns against the Western Turks , known as the Western Tujue in Chinese sources , were a series of military campaigns conducted during the Tang Dynasty against the Western Turkic Khaganate in the 7th century CE . Early military conflicts were a result of the Tang interventions in the rivalry between the Western and Eastern Turks in order to weaken both . Under Emperor Taizong , campaigns were dispatched in the Western Regions against Karakhoja in 640 , Karasahr in 644 and 648 , and Kucha in 648 . The wars against the Western Turks continued under Emperor Gaozong , and the khaganate was annexed after Gen . Su Dingfang ' s defeat of Qaghan Ashina Helu in 657 . The Western Turks attempted to capture the Tarim Basin in 670 and 677 , but were repelled by the Tang . The Second Turkic Empire defeated the fragmented Western Turks in 712 , and absorbed the tribes into the new empire . The areas controlled by Tang China came under the dynasty ' s cultural influences and the Turkic influence of the ethnically Turkic Tang soldiers stationed in the region . Indo - European prevalence in Central Asia declined as the expeditions accelerated Turkic migration into what is now Xinjiang . By the end of the 657 campaign , the Tang had reached its largest extent . The Turks , Tibetans , and the Tang competed for control over Central Asia until the collapse of the Tang in the 10th century . Background . The Gokturks split into the Western and Eastern Turkic Khaganates after a civil war . Allied with the Byzantine Empire , the Western Turks were mired in wars against the Sassanid Persians . The Western Turks expanded as the khaganate of the Eastern Turks declined . Early military conflicts . Emperor Gaozu , Taizong ' s predecessor , allowed the assassination of a Western Turk qaghan by Eastern Turkic rivals on November 2 , 619 . Emperor Taizong , in his war against the Western and Eastern Turks , employed the Chinese strategy of " using barbarians to control barbarians . " In 641 , he instigated a civil war between the eastern and western confederations of the Western Turks by supporting Isbara Yabghu Qaghan . The " qaghan " in the east , Tu - lu Qaghan , invaded the oasis states controlled by Isbara Yabghu in the west . He assassinated his rival and unified the Western Turkic Khaganate . Following the reunification , Tu - lu Qaghan began orchestrating raids against Chinese cities . In 642 , Emperor Taizong once again intervened by assisting a revolt against Tu - lu ' s reign . Disaffected Western Turkic tribes had requested the support of Taizong in Chang ' an , who enthroned a new " qaghan " Irbis Seguy . Irbis Seguy was able to exert control over the Turkic tribes and the former qaghan fled in exile . The Tang court and the Western Turks began negotiating over the control of five oasis states in the Tarim Basin . Irbis Seguy wanted to strengthen his ties with the Tang through a royal marriage with a Tang princess . Although the oasis states were vassals of the Turks , Irbis Seguy did not have the power to simply cede them to the Tang . The possibility of further diplomatic exchanges ended when Taizong began his invasion of the Tarim Basin . Campaigns against the Tarim Basin oasis states . Campaign against Karakhoja . Karakhoja had been ruled by the Qu family since 498 . The most sinicized of the oasis states , Karakhoja had adopted Chinese script as its official script , the Chinese classics as a subject for study , and an imperial bureaucracy . As the oasis state nearest to Tang China , the Chinese constituted a large portion of Karakhoja ' s population . Karakhoja also served as China ' s main Silk Road trade route into Central Asia . The route was severed when the Western Turk Tu - lu Qaghan , enthroned in 638 , promised Karakhoja military support . Campaigns against Karasahr . In 632 , Karasahr submitted to the Tang as a tributary state , as did the nearby kingdoms of Kashgar and Khotan . Tensions between Tang and Karasahr grew as the Chinese expanded further into Central Asia , and peaked when the Tang defeated and annexed Gaochang . The Chinese forces stationed in Gaochang , a short distance away from Karasahr , posed a direct threat to the oasis state . Karasahr allied with the Western Turkic Khaganate and ceased sending tributes to the Tang court . A military campaign was dispatched by the Tang emperor against Karasahr . Led by Commander Guoxiao Ke , protectorate - general of the Anxi Protectorate , the army marched towards Karasahr from Yulduz . The Tang forces mounted a surprise attack at dawn , resulting in the annexation of Karasahr and the capture of its king . The Western Turk army to retake Karashar was defeated by the Tang . Karasahr was controlled by proxy through a Tang loyalist , Long Lipozhun , brother of the captured ruler . He was deposed in 644 by his cousin , with the support of the kingdom of Kucha , nominally a Tang vassal , and the Western Turks . In 648 , the Tang conducted a second military campaign against Karasahr , commanded by Ashina She ' er , a member of the Turkic Ashina royal family . Karasahr fell , the usurper was beheaded , and Tang rule was re - established under another Tang loyalist . A Chinese military garrison was established in the kingdom , the first of the Four Garrisons of Anxi . Campaign against Kucha . After the fall of Karasahr , Ashina Sh ' er ' s army marched towards the neighboring kingdom of Kucha . She ' er ' s decoy horsemen led the defending Kucha forces , numbering 50 , 000 soldiers , into an ambush . The Kucha soldiers retreated to the nearby city of Aksu after their defeat . The Tang army besieged the city for forty days . Kucha surrendered on 19 January 649 and She ' er captured the king . By employing diplomacy , the surrounding tribes loyal to Kucha submitted to the Tang . Campaign against the Western Turks . Ashina Helu , a former Tang general in Gansu , fled west and declared himself qaghan of the Western Turks , unifying the Turkic tribes under a single khaganate . Helu invaded the kingdoms of the Tarim Basin and led frequent raids against bordering Tang cities . Emperor Gaozong sent an army led by Su Dingfang to defeat the Western Turks . The Turkic commanders Ashina Misha and Ashina Buzhen , rivals of Helu , led the side divisions . Ten thousand Uyghur horsemen participated in the campaign as allies of the Tang . Porun , an Uyghur leader enthroned by Emperor Taizong , oversaw the Uyghur cavalry as a vice commander . He served under the leadership of the Yanran Protector - General and Vice Protector - General , administrators of the Yanran Protectorate . The army departed from Ordos in march and traversed through 3 , 000 miles of steppes and desert , without stopping by the oasis kingdoms for supplies . Along the way , tribes like the Chumkun and Su offered additional reinforcements . The troops reached the Kyrgyzstan by November , enduring the harsh conditions of the winter . Su Dingfang defeated Helu ' s army of 100 , 000 calvalry at the battle of Irtysh River , fought along the Irtysh River in the Altai Mountains region . Helu had been caught off guard by Su ' s ambush and suffered a large amount of casualties . The qaghan attempted to flee to Tashkent , but was caught the next day and sent to the Tang capital as a prisoner . The remaining tribes of the Western Turks surrendered . Gaozong pardoned Helu , but the qaghan died the following year . Further campaigns . The dissolution of the khaganate fragmented the Western Turkic tribes . In 670 , a Western Turkic tribe allied with the Tibetan Empire and invaded the Tarim Basin . The Anxi protectorate was abandoned and the Tang withdrew back to Turfan . Control of the oasis states returned to the Tang between 673 and 675 , and the protectorate was re - established . In 677 , the Western Turks conducted a second military expedition with the Tibetans against the Tang in the Tarim Basin . The Turks were repelled by the Tang and defeated in 679 . Tang forces captured the leader of the Western Turks and annexed Tokmak , which was transformed into a military base . Ilterish Qaghan founded the Second Turkic Empire after a successful revolt in 682 . The expansion of the khaganate continued under Itlerish ' s brother , Qapaghan Qaghan . In 712 , Kul Tigin , son of Ilterish , defeated the remnants of the Western Turks , members of the Turgis confederation . Now defeated , the Western Turks were absorbed into the new empire . Historical significance . The Tang campaigns marked the end of Indo - European Xinjiang , as Turkic linguistic and cultural influences spread into Central Asia . Tang China was responsible for the influx of Turkic migrants , because of the number of Turks that served in the Tang military as soldiers and generals during the dynasty ' s military expeditions . Tang influence in the Central Asia encompassed art , trade , and politics . Chinese coinage remained in use in Xinjiang after the Tang withdrew from the region . Central Asian art adopted many Tang Chinese stylistic elements , like the sancai three color glaze used for ceramics . According to Chinese sources , Turkic empires still valued ties with the courts of dynasties in northern China as a form of prestige . The Qarakhan and Qarakhitay khans held titles that identified them as Tabghach or Khitay , named after kingdoms in northern China . Tang architectural influences are apparent in the Buddhist architecture in Dunhuang .