Emperor Taizong ' s campaign against Tuyuhun Emperor Taizong of Tang ( r . 626 - 649 ) , the second emperor of Chinese dynasty Tang Dynasty , throughout most of his reign , faced challenges from Tang ' s western neighbor , the state of Tuyuhun , whose Busabuo Khan Murong Fuyun constantly challenged Chinese authority in the border regions . In 634 , Emperor Taizong launched a major attack , commanded by the major general Li Jing , against Tuyuhun , dealing Tuyuhun forces heavy defeats and causing Murong Fuyun ' s subordinates to assassinate him in 635 . Tuyuhun , thus weakened , no longer remained a major power in the region , and while Tang , ironically , played the role of protector for Murong Fuyun ' s son , the Gandou Khan Murong Shun , and grandson , the Ledou Khan Murong Nuohebo , Tuyuhun was never able to recover , particularly with its southwestern neighbor Tufan constantly attacking it . By 672 , during the reign of Emperor Taizong ' s son Emperor Gaozong of Tang , Tang was forced to move Tuyuhun remnants into its own territory , ending Tuyuhun . During Murong Fuyun ' s reign . Throughout the reign of Emperor Taizong ' s father Emperor Gaozu , there were repeated cycles of Tuyuhun , then ruled by the Busabo Khan Murong Fuyun , making incursions into the modern Sichuan and southern Gansu regions and offers of peace by both sides , never longstanding . These incursions continued after Emperor Taizong became emperor in 626 — although they appeared to decrease in frequency , as the only incursions recorded in the Chinese chronicle " Zizhi Tongjian " were in 628 , when Tuyuhun forces attacked Min Prefecture ( 岷州 , roughly modern Dingxi , Gansu ) , and 632 , when Tuyuhun forces attacked Lan Prefecture ( 蘭州 , roughly modern Lanzhou , Gansu ) . It was said that , with regard to Tuyuhun ' s generally hostile attitude toward Tang , that Murong Fuyun had , in his old age ( although it is not known what his age was at this point ) , taken the posture at the advice of his strategist , the Prince of Tianzhu . Sometime before 634 , Murong Fuyun appeared to make an overture toward peace — by sending an emissary to offer tributes to Emperor Taizong — but even before the emissary left , Tuyuhun forces attacked and pillaged Shan Prefecture ( 鄯州 , in modern Haidong Prefecture , Qinghai ) . When Emperor Taizong sent emissaries to rebuke Murong Fuyun and summoned Murong Fuyun to Chang ' an to meet him , Murong Fuyun refused , but responded by requesting that a Tang princess be given to his son , the Prince of Zun , in marriage . Emperor Taizong agreed , but ordered that the Prince of Zun personally arrive in Chang ' an to marry the princess . When the Prince of Zun failed to do so , Emperor Taizong cancelled the marriage . Meanwhile , Murong Fuyun also attacked Lan and Kuo ( 廓州 , also in modern Haidong ) Prefectures and detained the Tang emissary Zhao Dekai ( 趙德楷 ) . Emperor Taizong sent a number of emissaries to Tuyuhun to discuss the matter and also summoned Tuyuhun emissaries and personally had discussions with them . Murong Fuyun still did not relent . In fall 634 , Emperor Taizong sent the generals Duan Zhixuan ( 段志玄 ) and Fan Xing ( 樊興 ) to attack Tuyuhun with Tang forces , supplemented by soldiers from the Qibi ( 契苾 ) and Dangxiang tribes . When Duan began the attack , however , after minor successes , Tuyuhun forces simply began to elude him and refuse to engage him . Apparently immediately after he withdrew , Tuyuhun forces again attacked Liang Prefecture ( 涼州 , roughly modern Wuwei , Gansu ) . In 634 the Tibetans asked the Chinese for a Chinese princess to marry their king . When they discovered that the Tuyuhun had an envoy in the capital at the same time also asking for the hand of a Chinese princess , they attacked the Tuyuhun forcing its king to flee . After further struggles between the Chinese and Tibetans , the Chinese finally agreed to send a princess to the Tibetan Emperor . Li Jing ' s campaign . After the Tuyuhun attack on Liang Prefecture , Emperor Taizong decreed that a major campaign against Tuyuhun shall be carried out . He wanted to make the general Li Jing his commander , but felt that Li Jing was getting advanced in age ( 63 at the time ) , and initially decided not to do so . However , when Li Jing heard this , he requested to go , which pleased Emperor Taizong , who made him the commander of the overall operation , with Hou Junji , Li Daozong , Li Daliang ( 李大亮 ) , Li Daoyan ( 李道彥 ) , and Gao Zengsheng ( 高甑生 ) serving under him , supplemented by Tujue and Qibi troops . In the initial stage of the campaign , some Dangxiang and Qiang tribes , apparently fearing that they would be involved , rebelled against Tang and fled to join Tuyuhun . In summer 635 , Tang forces began engaging Tuyuhun forces , and after some minor victories by Li Daozong , Murong Fuyun , apparently following the same strategies he used against Duan , burned the grasses and fled . Most of Li Jing ' s subordinates believed that it was dangerous to venture further without adequate grazing supplies and advised withdrawal , but Hou opposed the idea , pointing out that this was the opportunity to destroy Tuyuhun . Li Jing agreed , and divided his forces into two branches — with Li Jing himself , Xue Wanjun ( 薛萬均 ) and Li Daliang heading northwest , and Hou and Li Daozong heading southwest . Both prongs continued to be successful , although during one battle Xue Wanjun and his brother Xue Wanche ( 薛萬徹 ) fell into a Tuyuhun trap and were nearly killed , saved only by the heroics of Qibi Heli ( 契苾何力 ) . Eventually , Li Jing received news of Murong Fuyun ' s location and surprised Murong Fuyun , defeating his remaining forces . Murong Fuyun himself managed to flee , but the nobles , led by his son Murong Shun the Prince of Daning — who , as Murong Fuyun ' s oldest son by his wife , Sui Dynasty ' s Princess Guanghua , had been resentful at not being made crown prince — killed the Prince of Tainzhu and surrendered . Murong Fuyun , in flight , was killed by his subordinates . Emperor Taizong created Murong Shun the dual titles of Prince of Xiping and Zhugulüwugandou Khan ( or Gandou Khan in short ) , to succeed Murong Fuyun . Aftermaths . During Murong Shun ' s and Murong Nuohebo ' s reigns . Murong Shun ' s reign was short — plagued by the people ' s lack of respect for him , because he had long served as a hostage to Sui . In winter 635 , he was assassinated . His son Murong Nuohebo the Prince of Yan succeeded him , and there was much infighting . Emperor Taizong sent Hou Junji to Tuyuhun with an army to pacify the Tuyuhun people so that they would submit to Murong Nuohebo ' s rule . In 636 , Murong Nuohebo petitioned to formally submit to Tang , and Emperor Taizong created him the dual titles of Prince of Heyuan and Wudiyebaledou Khan ( or Ledou Khan in short ) . Tuyuhun , however , was soon under the threat of the emerging power of Tufan . Sometime before 638 , Tufan ' s Songtsän Gampo , who had heard that Eastern Tujue ' s and Tuyuhun ' s khans had been able to marry Chinese princesses , also wanted to marry one , sending emissaries to offer tributes of gold , silver , and jewelry as bride price . Emperor Taizong refused , and when the emissary returned to Tufan , he blamed Murong Nuohebo for alienating Emperor Taizong from a marriage with Tufan . Songtsän Gampo , believing the emissary , attacked Tuyuhun , forcing the Tuyuhun people to flee north of the Qinghai Lake . Songtsän Gampo next attacked Tang ' s Song Prefecture ( 松州 , roughly modern Ngawa Tibetan and Qiang Autonomous Prefecture , Sichuan ) , claiming that he was " welcoming " the Tang princess . In 638 , a counterattack by the Tang general Niu Jinda ( 牛進達 ) , under Hou ' s command , defeated Tufan forces at Song Prefecture . Songtsän Gampo submitted a formal apology to Emperor Taizong , but still requested to marry a Tang princess , and this time Emperor Taizong agreed , eventually creating a daughter of a clansman as Princess Wencheng and marrying her to Songtsän Gampo in 640 — but , prior to that , creating another daughter of a clansman as Princess Honghua and marrying her to Murong Nuohebo in 639 , when Murong Nuohebo visited the Tang capital Chang ' an . However , soon the control of the Tuyuhun state fell under the chancellor the Prince of Xuan . It was rumored that the Prince of Xuan intended to seize Princess Honghua and then turn her and Murong Nuohebo to Tufan . In 641 , when Murong Nuohebo heard this , he fled to Shanshan to his general the Prince of Weixin . Meanwhile , the Tang military commander Xi Junmai ( 席君買 ) made a surprise attack against the Prince of Xuan , killing him and his two brothers , allowing Murong Nuohebo to return , albeit with the Tuyuhun people highly alarmed . Emperor Taizong sent his official Tang Jian ( 唐儉 ) to Tuyuhun to try to pacify the people . Final collapse of the Tuyuhun . Little is known about Murong Nuohebo ' s governance for years after this incident . In 660 — more than a decade after Emperor Taizong had died in 649 and been succeeded by his son Emperor Gaozong — Tufan ' s then - chancellor Lu Dongzan ( 祿東贊 ) sent his son Qizheng ( 起政 ) to attack Tuyuhun on account of Tuyuhun ' s status as Tang vassal , although the results of the attack were not mentioned in Chinese historical sources , but the attacks appeared to recurrent . Both Tuyuhun and Tufan submitted petitions to Emperor Gaozong accusing each other of crimes and requesting aid , and Emperor Gaozong declined both . In 663 , when the Tuyuhun official Suhe Gui ( 素和貴 ) surrendered to Tufan , he gave much details about Tuyuhun to Tufan , and a subsequent Tufan attack dealt devastating losses to Tuyuhun . Murong Nuohebo and Princess Honghua abandoned their territory and fled to Liang Prefecture with his remaining followers , largely ending the existence of Tuyuhun as a separate state , although the Tuyuhun people would not be formally adopted into the Tang governmental structure until 672 , when Murong Nuohebo was given a prefect title in a newly created Anle Prefecture ( 安樂州 , in modern Wuzhong , Ningxia ) .