Tang campaign against the Eastern Turks

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. 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 to the imperial title—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. In 623, Liu Heita, the last major challenger to Tang rule, was captured and killed by Emperor Gaozu's crown prince Li Jiancheng, marking the reunification of China under Tang rule. The Eastern Turkic Khaganate, to which 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 khaganate with his grandmother Empress Xiao and carried the title of Prince of Sui. The Turkic incursions were causing so many problems for the Tang that Emperor Gaozu considered burning the capital Chang'an to the ground and moving his seat to the modern southwestern Henan region, 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 Gaozu's 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 Turks), 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 abdicate in his favour. Li shimin took the throne as Emperor Taizong. Less than a month later, the Turkic ruler 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 with 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).

Détente 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.

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:


 * Yan Shigu opined that the Eastern Turkic people should continued to be settled north of the Yellow River, to remain in tribal form, as vassals.
 * Li Baiyao opined that, specifically, letting the Eastern Turkic Khaganate's people remain north of the Yellow River but be scattered, with a member of the Eastern Turkic Khaganate's Ashina clan serving as khan, but only over the Ashina, while other tribes within the Eastern Turkic Khaganate's people be given their own chieftains, with positions equivalent to the Ashina khan; he also opined that a protector general be placed at Dingxiang to govern over them.
 * Dou Jing (竇靜) opined that the Eastern Turkic Khaganate's chieftains and people should be scattered, and that daughters of imperial clan members be given to the chieftains as wives, to better control them as vassals.

Two key opinions, given by two chancellors, emerged from the discussion:


 * Wen Yanbo opined that the Eastern Turkic Khaganate's people should be settled in the northern prefectures within Tang borders, remaining in tribal form, on lands that were currently not settled.
 * Wei Zheng opined that the Eastern Turkic Khaganate's people should be outside of Tang boundaries on their own lands.

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:

"After Jiali Khan was defeated, his tribes all surrendered to me. I forgave their errors and approved of their turning to goodness, treating their officials as my old subordinates and their people as my people.  China values respect and righteouness and does not seek to destroy others.  I defeated the Eastern Turkic Khaganate to prevent Illig Qaghan from harming the people.  I did not covet his land or want to seize his livestock and people, and I long wanted to consider selecting a new khan for them.  That is why I settled their people south of the Yellow River to let them graze.  Since I agreed to select a khan for them, I should not turn back on my own words.  After the fall, I will send the Turkic Khaganate north of the Yellow River to their old territory to rebuild themselves.  The khan of Xueyantuo was created first, and the khan of the Eastern Turkic Khaganate is created second; the khan created first is greater than the khan created second. You will live north of the Gobi, and he will live south of the Gobi. You should both defend your own territory and comfort your own people. If you exceed your boundaries and attack each other, I will send troops to punish you both."

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:

"I have received blessings that I did not deserve, and I lead this tribe as its chief. I hope that for generations, we will continue to serve as a watchdog outside the empire's north door, guarding it. But we are still currently weak, and if Xueyantuo should attack us, we might not be able to stand.  If that happens, I request permission to withdraw within the Great Wall."

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:

"How do I not dare to follow the emperor's edict? But the Turkic Khaganate's people are treacherous and should not be trusted. Before the destruction of their state, they invaded China each year and continued to kill thousands of people.  I thought that, after the emperor defeated them, he would make them into slaves and reward them to the Chinese people, but instead the emperor raised them like his own sons and showed much grace to them.  Despite this, Ashina Jiesheshuai rebelled.  They look like humans, but have hearts like beasts, and should not be treated as humans.  I have received much grace from the emperor, and I have nothing to repay him for.  I am willing to kill the Turks for China."

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.

Notes and references

 * Zizhi Tongjian, vols. 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197.
 * Bo Yang Edition of the Zizhi Tongjian, vols. 44, 45, 46, 47.
 * Bo Yang, Outlines of the History of the Chinese (中國人史綱), vol. 2, pp. 509–512.
 * Old Book of Tang, vol. 194, part 1.
 * New Book of Tang, vol. 215, part 1.