Emperor Taizong ' s campaign against Eastern Tujue Emperor Taizong of Tang ( r . 626 - 649 ) , the second emperor of Chinese dynasty Tang Dynasty , faced a major threat from Tang ' s northern neighbor , the Eastern Turkic Khaganate , whom his father Emperor Gaozu of Tang had been subjugated by in several manners . Early in Emperor Taizong ' s reign , he placated the Eastern Turkic Khaganate ' s Jiali Khan Ashina Duobi , but , preparing for several years for a major offensive against the Eastern Turkic ( including forming an alliance with the Eastern Turkic Khaganate ' s restless vassal Xueyantuo , which was ready to throw off the Eastern Turkic yoke ) , he launched it in winter 629 , with the major general Li Jing in command , and in 630 , after Li Jing captured Ashina Duobi , the Eastern Turkic Khaganate was destroyed . After the destruction of the Eastern Turkic Khaganate , the control of the territory north of Tang largely fell to Xueyantuo , and Emperor Taizong initially tried to settle a large number of the Eastern Turkic people within Tang borders . Eventually , after an incident where he was nearly assassinated by a member of the Eastern Turkic royal house , Ashina Jiesheshuai , he tried to resettle the Eastern Turkic people north of the Great Wall and south of the Gobi Desert , to serve as a buffer between Tang and Xueyantuo , creating a loyal Eastern Turkic Khaganate ' s prince Ashina Simo as the Qilibi Khan , but Ashina Simo ' s reign collapsed around new year 645 due to dissent within and pressure from Xueyantuo without , and Tang would not attempt to recreate the Eastern Turkic Khaganate any further ( although there were remnant tribes that rose later — and Eastern Turkic was , during the reign of Emperor Taizong ' s son Emperor Gaozong , reestablished under Ashina Gudulu , as a hostile power against Tang ) . Background . The Eastern Turkic Khaganate , which had been a vassal to Tang Dynasty ' s predecessor Sui Dynasty , had turned against Sui during the reign of Emperor Yang of Sui ( r . 604 - 618 ) and subsequently , during Sui ' s breakup late in Emperor Yang ' s reign , had intervened in the process by supporting various claimants of the right to succeed Sui — including Tang ' s founder Emperor Gaozu , Xue Ju the Emperor of Qin , Liang Shidu the Emperor of Liang , Liu Wuzhou the Dingyang Khan , Gao Kaidao the Prince of Yan , Dou Jiande the Prince of Xia , and Liu Heita the Prince of Handong , playing them off against each other to try to make them subservient to the Eastern Turkic Khaganate . After China had largely become reunited under Tang rule in 623 after Liu Heita , the last major challenger to Tang rule , was captured and killed by Emperor Gaozu ' s crown prince Li Jiancheng , the Eastern Turkic Khaganate , to whom Emperor Gaozu still paid allegiance and tributes , began a campaign of routine pillaging incursions into Tang territory , effectively asserting authority over Tang territory in that manner , while continuing to protect Liang , who remained as the sole Chinese claimant of imperial authority against Tang , and also fostering the aspirations of Emperor Yang ' s young grandson Yang Zhengdao ( 楊政道 ) , who was in the Eastern Turkic Khaganate with his grandmother Empress Xiao carried the title of Prince of Sui . The Eastern Turkic Khaganate incursions were causing so much problems for Tang that Emperor Gaozu considered burning the capital Chang ' an to the ground and moving the capital to the modern southwestern Henan region to avoid Turkic incursions , a proposal that was supported by Li Jiancheng , another son Li Yuanji the Prince of Qi , and the chancellor Pei Ji , but vehemently opposed by another son Li Shimin the Prince of Qin . Due to Li Shimin ' s opposition ( and guarantee that eventually he would be able to defeat the Eastern Turkic Khaganate ) , Emperor Gaozu abandoned the proposal . In 626 , Li Shimin , who had been locked in an intense rivalry with Li Jiancheng , ambushed and killed both Li Jiancheng and Li Yuanji ( who supported Li Jiancheng ) at Xuanwu Gate , and then effectively forced Emperor Gaozu to first make him crown prince and then yield the throne to him . He took the throne as Emperor Taizong . Less than a month after Emperor Taizong took the throne , Eastern Turkic Khaganate ' s Illig Qaghan ( Ashina Duobi ) and his nephew , the subordinate Tölis Qaghan ( Ashina Shibobi , 阿史那什鉢苾 ) , made a major incursion into Tang territory , this time advancing all the way to Chang ' an , shocking the Tang officials . Emperor Taizong was forced to personally meet them , give them and major Eastern Turkic officials gifts , and promise further tributes . Only after he did so did Ashina Duobi and Ashina Shibobi withdraw ( 渭水之盟 ) . Detente early in Emperor Taizong ' s reign . For the next several years , there was relative peace between Tang and the Eastern Turkic Khaganate . Meanwhile , it was said that Ashina Duobi ' s governance was deteriorating — as the Eastern Turkic Khaganate ' s laws had been lax and simple , but Ashina Duobi entrusted much government function to the Chinese man Zhao Deyan ( 趙德言 ) , who abused his power and instituted complicated regulations , causing the people to be alienated . Moreover , it was said that Ashina Duobi trusted the ethnic Xiongnu rather than his own Turkic people , leading to a number of rebellions that Ashina Duobi had to suppress . By 627 , Emperor Taizong , hearing this , was contemplating attacking the Eastern Turkic Khaganate , and he consulted the chancellor Xiao Yu and his brother - in - law Zhangsun Wuji . Xiao advocated attacking , but Zhangsun , pointing out that the Eastern Turkic Khaganate had not attacked and therefore there was no good reason to break the peace , opposed , and Emperor Taizong did not attack the Eastern Turkic Khaganate . At the same time , however , Xueyantuo , which had been a vassal of both the Eastern Turkic Khaganate and the Western Turkic Khaganate at times , was beginning to strengthen , as was another vassal of the Eastern Turkic Khaganate , Huige , and Ashina Duobi was unable to defeat or contain them . Ashina Duobi ' s relationship with Ashina Shibobi was also deteriorating — as he had put the eastern part of the state under Ashina Shibobi ' s responsibility and blamed Ashina Shibobi for the gradual peeling away by the vassals Khitan and Xi tribes to the east . Further , when he sent Ashina Shibobi against Xueyantuo and Huige , Ashina Shibobi was unable to prevail over them . Ashina Duobi put Ashina Shibobi under arrest for a number of days before releasing him , and once Ashina Shibobi returned to his troops , he refused to follow Ashina Duobi ' s orders any more , drawing an attack from Ashina Duobi in 628 . Emperor Taizong , who had sworn to be a blood brother of Ashina Shibobi on a prior occasion , agreed to launch troops to protect Ashina Shibobi — and at the same time , was using the opportunity to attack Liang Shidu , who by this point was still under the Eastern Turkic Khaganate ' s protection . With much internal troubles , Ashina Duobi was unable to aid Liang , and later in 628 , with Emperor Taizong ' s brother - in - law Chai Shao ( 柴紹 ) sieging Liang ' s capital Shuofang ( 朔方 , in modern Yulin , Shaanxi ) , Liang Shidu ' s cousin Liang Luoren ( 梁洛仁 ) assassinated Liang Shidu and surrendered , ending the final rival claim to Emperor Taizong ' s for China ' s imperial throne . Around the same time , the Xueyantuo tribes had coalesced around the leadership of a chieftain , Yi ' nan , although Yi ' nan initially declined the offer of the title of khan . When Emperor Taizong heard this , however , he sent the general Qiao Shiwang ( 喬師望 ) to Xueyantuo to create Yi ' nan Zhenzhupiqie Khan ( or Zhenzhu Khan for short ) , creating an alliance with Xueyantuo . When Ashina Duobi heard this , he sought long - term peace in forms of a marriage to a Tang princess , which Emperor Taizong did not answer . Instead , he prepared for a major assault on the Eastern Turkic Khaganate , with the major general Li Jing commanding and with the general Zhang Gongjin ( 張公謹 ) assisting Li Jing . Li Jing ' s expedition . Li Jing commanded the main prong of the attacks against the Eastern Turkic Khaganate , with the generals Li Shiji , Xue Wanche ( 薛萬徹 ) , and Chai Shao commanding the other prongs , but with Li Jing in overall command . In spring 630 , Li Jing ' s forces , surprising Ashina Duobi ' s , captured Dingxiang ( 定襄 , in modern Hohhot , Inner Mongolia ) , approaching Ashina Duobi ' s imperial tent . He then sent spies to Ashina Duobi ' s camp and persuaded a number of Ashian Duobi ' s close associates , including Kangsumi ( 康蘇密 ) , to surrender ( along with Sui ' s Empress Xiao and her grandson Yang Zhengdao ) . Ashina Duobi withdrew to the Yin Mountains and offered to submit to Tang — but at the same time he was negotiating with the Tang envoy Tang Jian ( 唐儉 ) , whom Emperor Taizong sent to negotiate with him , he was considering withdrawing further , north of the Gobi Desert . Li Jing and Li Shiji , believing that Ashina Duobi was merely stalling for time , joined their forces and attacked Ashina Duobi , defeating him and killing his wife ( Sui Dynasty ' s Princess Yicheng ) . Ashina Duobi fled further to his subordinate khan Ashina Sunishi ( 阿史那蘇尼失 ) , but was soon captured by the Tang general Zhang Baoxiang ( 張寶相 ) and delivered to Chang ' an . Turkic nobles largely surrendered to Tang , while the Turkic Khaganate ' s people scattered in three directions — either surrendering to Tang , surrendering to Xueyantuo , or fleeing west to the Western Turkic Khaganate and the nearby kingdoms . Aftermaths . Initial attempt to settle Eastern Turkic Khaganate ' s people within the Tang state . Emperor Taizong requested opinions from his officials as to what to do with the Eastern Turkic Khaganate ' s people , and it was said that the majority opinion was to move them to the modern Shandong and Henan region and scatter them within Tang prefectures to sinicize them , making them unable to reorganize . However , there were several officials who held differing opinions whose opinions were recorded in historical records : Two key opinions , given by two chancellors , emerged from the discussion : Emperor Taizong eventually accepted Wen ' s opinions , establishing four nominal prefectures over Ashina Shibobi ' s people and six nominal prefectures over Ashina Duobi ' s people , with two commandants governing over the people . Ashina Sunishi and another Eastern Turkic Khaganate ' s prince , Ashina Simo ( who , in particular , was given the Tang imperial surname Li and therefore also known as Li Simo ) , were created princes , and a large number of other chieftains were given general ranks ; they were settled in or near Chang ' an . Emperor Taizong also gave the Eastern Turkic Khaganate ' s people who possessed Han people as slaves ransoms and had them return those Han slaves to Tang . Also thereafter , Emperor Taizong often requisitioned Turkic cavalry soldiers to supplement regular Tang troops on various campaigns , such as the 634 campaign against Tuyuhun . Meanwhile , Xueyantuo largely took over Eastern Turkic Khaganate ' s former territory , with most of Eastern Turkic Khaganate ' s former vassals submitting to it . Yi ' nan remained nominally submissive to Tang , remaining formally respectful to Emperor Taizong , while at the same time trying to affirm Xueyantuo ' s control over the region . Former Eastern Turkic Khaganate ' s vassals Khitan , Xí ( 霫 ) , and Xĩ tribes directly submitted to Tang , as did the city kingdom of Yiwu ( 伊吾 ) . Brief attempt to recreate Eastern Turkic Khaganate under Ashina Simo . In 639 , a conspiracy to assassinate Emperor Taizong came into shape , led by Ashina Shibobi ' s brother Ashina Jiesheshuai . Ashina Jiesheshuai was said to live immorality and corruptly , and when Ashina Shibobi rebuked him , he resented Ashina Shibobi and falsely accused Ashina Shibobi of treason . Emperor Taizong , because the false accusation , disliked Ashina Jiesheshuai and long refused to promote him . Ashina Jiesheshuai therefore formed a conspiracy with 40 - some of his former subordinates and Ashina Shibobi ' s son Ashina Hexian ' gu ( 阿史那賀暹鶻 ) , and on May 19 , 639 , they hid around outside Emperor Taizong ' s palace , intending to charge into the palace when the palace gates would be opened to allow Emperor Taizong ' s son Li Zhi the Prince of Jin to exit in the morning at dawn . However , the wind was high that morning , and Li Zhi did not exit the palace early ; as Ashina Jiesheshuai was concerned about being discovered after dawn , he started attaacking the palace gates anyway . His men killed some tens of imperial guards , but could not progress against the resistance of the imperial guard commander Sun Wukai ( 孫武開 ) . Ashina Jiesheshuai eventually took imperial guards ' horses and fled , attempting to flee north . He and his followers were captured and executed , except for Ashina Hexian ' gu , who was exiled . After Ashina Jiesheshuai ' s assassination attempt , Emperor Taizong , with voices coming from a number of officials , decided that it was not advisable to keep the Turkic people within the borders . On August 13 , 639 , he created Ashina Simo as the Yiminishuqilibi Khan ( or Qilibi Khan for short ) and ordered the settled Turkic and Xiongnu people to follow Ashina Simo north of the Yellow River to settle between the Great Wall and the Gobi Desert . The Turkic Khaganate ' s people , fearful of Xueyantuo , initially refused . Emperor Taizong thereafter issued an edict to Yi ' nan , delivered by his official Guo Siben ( 郭嗣本 ) , stating : Yi ' nan , while unhappy with Eastern Turkic Khaganate ' s reestablishment , indicated that he would submit . The Turkic people were thus willing to follow Ashina Simo north of the Yellow River , and the Eastern Turkic Khaganate was reestablished as a Tang vassal . Emperor Taizong also created the princes Ashina Zhong ( 阿史那忠 , Ashina Sunishi ' s son ) and Ashina Nishou ( 阿史那泥熟 ) as assistants for Ashina Simo — although , perhaps foreshadowing what would eventually happen , Ashina Zhong was said to miss life in Chang ' an so much that each time imperial emissaries were sent to the Eastern Turkic Khaganate , he begged them to intercede to allow him to return to Chang ' an , a request that Emperor Taizong eventually approved . In spring 640 , Emperor Taizong established a general post near the Eastern Turkic Khaganate to help defend it . In spring 641 , Ashina Simo ' s people finally crossed the Yellow River , and he established his headquarters at Dingxiang . He was said to have 30 , 000 households , 40 , 000 troops , and 90 , 000 warhorses . He submitted a petition to Emperor Taizong , stating : Emperor Taizong agreed . In winter 641 , indeed , with Yi ' nan anticipating that Emperor Taizong would soon be offering sacrifices to heaven and earth at Mount Tai and would take his soldiers with him , he believed that he could destroy Ashina Simo quickly . He therefore had his son Dadu ( 大度 ) to head Xueyantuo troops , along with conscripted troops from vassal tribes Tongluo ( 同羅 ) , Pugu ( 僕骨 ) , Huige , Mohe , and Xí , launch a major attack on the Eastern Turkic Khaganate . Ashina Simo could not resist the attack , and withdrew within the Great Wall to Shuo Prefecture ( 朔州 , roughly modern Shuozhou , Shanxi ) and sought emergency aid . Emperor Taizong sent the generals Zhang Jian ( 張儉 ) , Li Shiji , Li Daliang ( 李大亮 ) , Zhang Shigui ( 張士貴 ) , and Li Xiyu ( 李襲譽 ) , to attack Xueyantuo to assist Ashina Simo , with Li Shiji in overall command . Around the new year 642 , Li Shiji dealt a major defeat to Dadu , who fled after heavy casualties . Emperor Taizong , while sending an emissary to rebuke Yi ' nan , did not take further actions from Xueyantuo at this point . It was said that Yi ' nan continued to be unhappy with Eastern Turkic Khagante ' s existence , and continued to harass the Eastern Turkic Khaganate . ( Yi ' nan , however , tried to maintain peaceful relations with Tang , and at one point was engaged to marry Emperor Taizong ' s daughter Princess Xinxing , but Emperor Taizong regretted the marriage agreement and broke it in 643 under the pretense that Yi ' nan ' s offer of bride price ( with livestock ) was not paid for on time . ) When Emperor Taizong sent further emissaries to order Yi ' nan from attacking the Eastern Turkic Khaganate , Yi ' nan ' s response was : Around the new year 645 , Ashina Simo ' s people , apparently under the Xueyantuo pressure , collapsed and abandoned Ashina Simo . ( At this time , Emperor Taizong was deep in his preparation to attack Goguryeo , and therefore , if Xueyantuo had attacked , might not have been able to protect the Eastern Turkic Khaganate . ) They crossed the Yellow River south , seeking to be settled among Sheng ( 勝州 , also in modern Hohhot , but south of the Yellow River ) and Xia ( 夏州 , roughly modern Yulin ) Prefectures . Despite officials ' opposition , Emperor Taizong agreed , and did so . Ashina Simo , with his reconstituted state in shambles , also returned to China , and was again made a Tang general , ending Tang ' s attempt to recreate the Eastern Turkic Khaganate as a vassal . Later campaign against Ashina Tuobo . Yi ' nan remained formally submissive to Tang , but after Yi ' nan ' s death in 645 , Yi ' nan ' s son and successor , the Duomi Khan Bazhuo , took a hostile stance against Tang , and Tang and Huige forces subsequently destroyed Xueyantuo in 646 . Meanwhile , there had been a remnant Eastern Turkic Khaganate ' s prince , Ashina Hubo , who had not submitted to Xueyantuo previously and had settled to the north of Xueyantuo , and who by now was claiming the title of Yizhuchebi Khan ( or Chebi Khan in short ) , who tried to reestablish the Eastern Turkic Khaganate as a power . In winter 647 , Ashina Hubo sent his son Ashina Sabolo ( 阿史那沙鉢羅 ) to Tang to offer tributes , and he also offered to personally visit Emperor Taizong . Emperor Taizong sent the general Guo Guangjing ( 郭廣敬 ) to escort him , but Ashina Hubo had no actual intentions of departing for China and did not do so . In spring 649 , Emperor Taizong responded by sending the general Gao Kan ( 高侃 ) north against Ashina Hubo , along with troops from Huige and Pugu ( 僕骨 ) tribes . Emperor Taizong himself died in summer 649 , during the pendency of the campaign , which eventually led to Gao ' s victory over Ashina Hubo , capturing him . In fall 650 , Gao returned to Chang ' an with Ashina Hubo , whom Emperor Taizong ' s son and successor Emperor Gaozong released and made a general , ending ( for the time being ) an attempt to rebuild the Eastern Turkic Khaganate .