Early life

Li Shimin was born in 598 at Wugong, in modern Xianyang, Shaanxi. His father Li Yuan, the Duke of Tang, was a general of the Sui dynasty, and a nephew, by marriage, to Sui's founding emperor Emperor Wen. Li Shimin's grandmother Duchess Dugu was a sister of Empress Dugu, both of whom were daughters of Dugu Xin, a major Xianbei general during Sui's predecessor dynasty Northern Zhou. Li Shimin's mother, Li Yuan's wife Duchess Dou, was a daughter of Dou Yi, the Duke of Shenwu, and his wife, Northern Zhou's Princess Xiangyang. Li Shimin was also of partial Xianbei descent. Duchess Dou bore Li Yuan four sons—an older brother to Li Shimin, Li Jiancheng, and two younger brothers, Li Yuanba (李元霸), who would die in 614, and Li Yuanji – and at least one daughter (the later Princess Pingyang). Li Yuan named Li Shimin "Shimin" as a shortened form of the phrase "save the earth and pacify the people" (济世安民 jìshì ānmín). Li Shimin apparently showed talent early in his life, and in 613, the official Gao Shilian, impressed with him, gave him a niece (the later Empress Zhangsun) in marriage as his wife; he was 14 and she was 12. In 615, when Emperor Wen's son and successor Emperor Yang was ambushed by Eastern Turkic (Dongtujue) forces under Shibi Khan at Yanmen Commandery (present-day Daixian in Shanxi), a general call was made for men to join the army to help rescue the emperor. Li Shimin answered that call and served under the general Yun Dingxing, apparently doing so with distinction. In 616, when Li Yuan was put in charge of the important city of Taiyuan, he brought Li Shimin with him to Taiyuan, while leaving at least three other sons – Li Jiancheng, Li Yuanji, and Li Zhiyun (, by Li Yuan's concubine Lady Wan) – at the ancestral home Hedong (, in modern Yuncheng, Shanxi).

Participation in the rebellion against Sui rule

Emperor Yang was soon dissatisfied with Li Yuan and Wang Rengong (王仁恭), the governor of Mayi Commandery (, roughly modern Shuozhou, Shanxi), over their inability to stop Eastern Turkic incursions and the growing strength of agrarian rebels, particularly the Eastern Turkic-supported Liu Wuzhou, who soon rose against Wang, killed him, and captured Emperor Yang's secondary palace near Taiyuan. Li Yuan also became fearful of a prophecy that the next emperor would be named Li—Emperor Yang had previously killed another official, Li Hun, and Li Hun's clan over his fear that Li Hun's nephew, Li Min (李敏), would seize the throne.

Fearful for his life, Li Yuan considered rebellion. However, he did not know that Li Shimin had also been secretly discussing plans for rebellion with Li Yuan's associates Pei Ji and Liu Wenjing. Once Li Shimin's plans matured, he had Pei inform Li Yuan of them—and also had Pei warn Li Yuan that if it were revealed that Li Yuan had had sexual relations with some of Emperor Yang's ladies in waiting at the secondary Jinyang Palace (, which Pei was in charge with and had allowed Li Yuan to do so), all of them would be slaughtered. Li Yuan agreed to rebel, and after secretly summoning Li Jiancheng and Li Yuanji from Hedong and his son-in-law Chai Shao (柴绍) from the capital Chang'an, he declared a rebellion, claiming to want to support Emperor Yang's grandson Yang You the Prince of Dai, nominally in charge at Chang'an with Emperor Yang at Jiangdu (江都, in modern Yangzhou, Jiangsu), as emperor. He made both Li Jiancheng and Li Shimin major generals and advanced southwest, toward Chang'an. He gave Li Shimin the title of Duke of Dunhuang. After defeating local Sui forces loyal to Emperor Yang, he defeated a Sui army of 30,000 men under the command of a veteran general of the wars in Korea outside of modern-day Beijing.

However, when Li Yuan arrived near Hedong, his army was bogged down by the weather. With food running out, there were rumors that the Eastern Turks and Liu Wuzhou would attack Taiyuan. Li Yuan initially ordered retreat, but at the earnest opposition by Li Jiancheng and Li Shimin, continued to advance. After defeating Sui forces at Huoyi (霍邑, also in modern Yuncheng), he decided to leave a small contingent to watch over Hedong while advancing across the Yellow River into Guanzhong (i.e., the Chang'an region). Once he did, he headed for Chang'an himself, while sending Li Jiancheng to capture the territory around the Tong Pass region to prevent Sui forces at Luoyang from reinforcing Chang'an and Li Shimin north of the Wei River to capture territory there. Meanwhile, Li Shimin's sister Pingyang had also risen in rebellion in support of him, and she was able to gather a sizeable army and capture some cities. She joined forces with Li Shimin and her husband Chai Shao. Soon, Li Yuan reconsolidated his forces and put Chang'an under siege. In winter 617, after defeating a large Sui army, he captured Chang'an from imperial forces and declared Yang You emperor (as Emperor Gong). He had himself made regent (with the title of grand chancellor), Li Shimin made the Duke of Qin, and created the Prince of Tang. Meanwhile, most of the Sui territories and armies did not recognize Emperor Gong as emperor, continuing to support the former Emperor Yang.

Li Yuan's control of the Chang'an region became almost immediately contested by the rebel ruler Xue Ju, the Emperor of Qin, who sent his son Xue Rengao toward Chang'an. Li Yuan sent Li Shimin to resist Xue Rengao, and Li Shimin defeated Xue Rengao at Fufeng (in modern Baoji, Shaanxi), temporarily causing Xue Ju to toy with the idea of surrendering to Li Yuan, although Xue was subsequently dissuaded by his strategist Hao Yuan (郝瑗) from doing so.

In spring 618, with Sui's eastern capital Luoyang (where the officials in charge did not recognize Li Yuan's authorities) under attack by the rebel ruler Li Mi the Duke of Wei, Li Yuan sent Li Jiancheng and Li Shimin to Luoyang, ostensibly to aid the Sui forces at Luoyang but instead intending to test whether Luoyang might submit to him. The officials at Luoyang rebuffed his attempt at rapprochement, and Li Jiancheng and Li Shimin, not wanting to fight either them or Li Mi for control of Luoyang at this stage, withdrew. Li Yuan subsequently changed Li Shimin's title to Duke of Zhao.

In summer 618, when news arrived at Chang'an that Emperor Yang had been killed at Jiangdu in a coup led by the general Yuwen Huaji, Li Yuan had Emperor Gong yield the throne to him, establishing Tang dynasty as its Emperor Gaozu. He created Li Jiancheng crown prince but created Li Shimin the Prince of Qin, also making him Shangshu Ling, the head of the executive bureau of the government (尚书省 Shàngshū Shěng) and a post considered one for a chancellor, while continuing to have Li Shimin serve as a major general as well.

During Emperor Gaozus reign

Campaign to reunify the empire

The first thing that Li Shimin had to deal with was another incursion by Xue Ju, as Xue attacked Jing Prefecture (, roughly modern Pingliang, Gansu) and Emperor Gaozu sent Li Shimin to resist Xue. Li Shimin established his defenses and refused to engage Xue to try to wear Xue Ju out, but at that time, he was afflicted with malaria, and he let his assistants Liu Wenjing and Yin Kaishan take command, ordering them not to engage Xue Ju. Liu and Yin, however, did not take Xue Ju seriously, and Xue Ju ambushed them at Qianshui Plain (, in modern Xianyang), crushing Tang forces and inflicting 50–60% casualties. Li Shimin was forced to withdraw back to Chang'an, and Liu and Yin were removed from their posts. (This would be Li Shimin's only defeat recorded in historical records until the Goguryeo campaign of 645.) Xue Ju, in light of his victory, was ready to launch an assault on Chang'an itself, under Hao Yuan's advice, but suddenly died of an illness in fall 618 and was succeeded by Xue Rengao. Emperor Gaozu then sent Li Shimin against Xue Rengao. Three months after Xue Rengao took the throne, Li Shimin engaged him, and after a fierce battle between Li Shimin and Xue Rengao's major general Zong Luohou, Li Shimin crushed Zong's forces, and then attacked Xue Rengao. Xue Rengao was forced to withdraw into the city of Gaozhi (高墌, in modern Xianyang as well), and once he did, his soldiers began surrendering to Li Shimin en masse. Xue Rengao was himself forced to surrender. Li Shimin had him delivered to Chang'an, where he was executed. Around new year 619, Emperor Gaozu made Li Shimin Taiwei (太尉, one of the Three Excellencies) and put him in charge of Tang operations east of the Tong Pass.

In spring 619, Liu Wuzhou launched a major offensive against Tang. He captured Taiyuan in summer 619, forcing Li Yuanji, who had been in charge there, to flee, and then continued his offensive south. Emperor Gaozu sent Pei Ji against him, but by winter 619, Liu had crushed Pei's forces and taken over nearly all of modern Shanxi. Emperor Gaozu, shocked at the development, considered abandoning the region altogether. Li Shimin opposed doing so and offered to lead the army against Liu. Emperor Gaozu agreed and commissioned him with an army. He crossed the Yellow River and approached Liu's major general Song Jingang but did not engage him, choosing to try to wear Song out, only having his subordinates Yin Kaishan and Qin Shubao engage the other Dingyang generals Yuchi Jingde and Xun Xiang in relatively low-level engagements. Eventually, in spring 620, when Liu and Song ran out of food supplies, they retreated, and Li Shimin gave chase, dealing Song a major defeat. Yuchi and Xun surrendered, and after Li Shimin chased further, both Liu and Song fled to the Eastern Turks. All of Dingyang territory fell into Tang hands.

In summer 620, Emperor Gaozu again commissioned Li Shimin against a major enemy—the former Sui general Wang Shichong, who had Sui's last emperor, Emperor Yang's grandson Yang Tong, yield the throne to him in 619, establishing a new state of Zheng as its emperor. When Li Shimin arrived at the Zheng capital Luoyang, Wang offered peace, but Li Shimin rebuffed him and put Luoyang under siege. Meanwhile, his subordinates took Zheng cities one by one. By winter 620, most of Zheng territory, other than Luoyang and Xiangyang, defended by Wang Shichong's nephew Wang Honglie (王弘烈), had submitted to Tang. Wang sought aid Dou Jiande the Prince of Xia, who controlled most of modern Hebei. Dou, reasoning that if Tang were able to destroy Zheng, his own Xia state would be next, agreed. He sent his official Li Dashi to try to persuade Li Shimin to withdraw, but Li Shimin detained Li Dashi and gave no response. Meanwhile, during the campaign, Li Shimin chose some 1,000 elite soldiers, clad in black uniform and black armor, commanded by himself, to serve as advance troops, with Qin Shubao, Yuchi Jingde, Cheng Zhijie, and Zhai Zhangsun as his assistants.

By spring 621, Luoyang was in desperate situation, and Xia forces had not yet arrived, but Tang troops had also suffered serious casualties, as Luoyang's defenses, aided by powerful bows and catapults, were holding. Emperor Gaozu, hearing that Dou had decided to come to Wang's aid, ordered Li Shimin to withdraw, but Li Shimin sent his secretary Feng Deyi to Chang'an to explain to Emperor Gaozu that if he did withdraw, Wang would recover and again be a major threat in the future. Emperor Gaozu agreed and allowed Li Shimin to continue to siege Luoyang. When Xia forward troops arrived first, Li Shimin surprised and defeated them, and then sent Dou a letter suggesting that he withdraw. Dou would not do so, and, against the advice of his wife Empress Cao and secretary general Ling Jing (凌敬) that he should instead attack Tang's prefectures in modern southern Shanxi, he marched toward Luoyang. Anticipating Dou's maneuver, Li Shimin left a small detachment, commanded by Li Yuanji, at Luoyang, while marching east himself, taking up position at the strategic Hulao Pass. When the armies engaged at Hulao, Li Shimin defeated Dou and captured him. He took Dou back to Luoyang and displayed him to Wang Shichong. Wang, in fear, considered abandoning Luoyang and fleeing south to Xiangyang, but as his generals pointed out that his only hope was Dou, he surrendered. Xia forces, after initially fleeing back to their capital Mingzhou (now Guangfu, Hebei), also surrendered. Zheng and Xia territory were Tang's. Li Shimin returned to Chang'an in a grand victory procession and, to reward Li Shimin, Emperor Gaozu awarded both him and Li Yuanji three mints so that they could mint money of their own. He also bestowed on Li Shimin the special title of "Grand General of Heavenly Strategies" (天策上将 tiāncè shàngjiàng). Meanwhile, Li Shimin's staff, already full of generals and strategists, were supplemented with a number of literary men.

The former Xia territory did not remain in Tang hands for long. In the winter of 621, the Xia general Liu Heita rose against Tang rule, claiming to be avenging Dou, whom Emperor Gaozu had executed against Li Shimin's wishes after he had been brought back to Chang'an. Liu was allied with Xu Yuanlang, a former agrarian rebel general who was nominally under Wang Shichong and who had submitted to Tang after Wang's defeat. Liu dealt successive defeats to Emperor Gaozu's cousin Li Shentong (李神通), the Prince of Huai'an; Li Xiaochang (李孝常), the Prince of Yi'an; and Li Shiji. By the end, he had recovered almost all of the former Xia territory, established his capital at Mingzhou, and proclaimed himself the Prince of Handong. Emperor Gaozu finally sent Li Shimin and Li Yuanji against him in 622 and, after some indecisive battles, Li Shimin defeated him by first erecting a dam across the Ming River and then destroying it, with the resultant flood destroying the rebel army. Liu fled to the Eastern Turks, while Li Shimin then headed east and defeated Xu. After leaving Li Shiji, Li Shentong, and Ren Gui to continue attacking Xu, Li Shimin returned to Chang'an.

Struggle against Li Jiancheng and Li Yuanji

By this point, Li Shimin and his older brother Li Jiancheng, who was created crown prince in 618, reportedly after Emperor Gaozu first offered the position to Li Shimin due to his contributions, were locked in an intense rivalry, as Li Shimin's accomplishments caused people to speculate that he would displace Li Jiancheng as crown prince, and Li Jiancheng, while an accomplished general himself, was overshadowed by his younger brother. The court became divided into a faction favoring the Crown Prince and a faction favoring the Prince of Qin. The rivalry was particularly causing problems within the capital, as the commands of the Crown Prince, the Prince of Qin, and the Prince of Qi Li Yuanji were said to have the same force as the emperor's edicts, and the officials had to carry conflicting orders out by acting on the ones that arrived first. Li Shimin's staff was full of talented men, but Li Jiancheng was supported by Li Yuanji, as well as Emperor Gaozu's concubines, who had better relationships with Li Jiancheng and Li Yuanji than they did with Li Shimin.

Late in 622, when Liu Heita returned east after receiving aid from the Eastern Turks, defeating and killing Li Shimin's cousin Li Daoxuan (李道玄), the Prince of Huaiyang, he again regained most of former Xia territory. Li Jiancheng's staff members Wang Gui and Wei Zheng suggested that Li Jiancheng needed to enhance his own reputation in battle, and so Li Jiancheng volunteered for the mission. Emperor Gaozu thus sent Li Jiancheng, assisted by Li Yuanji, to attack Liu. Li Jiancheng defeated Liu around the new year of 623, and Liu was subsequently betrayed by his own official Zhuge Dewei and delivered to Li Jiancheng. Li Jiancheng executed Liu in his former capital and returned to Chang'an in triumph. China was, by this point, roughly united under Tang rule.

For the next few years, the rivalry intensified, although during the meantime both Li Jiancheng and Li Shimin served as generals when the Eastern Göktürks made incursions. In 623, when the general Fu Gongshi rebelled at Danyang (, in modern Nanjing, Jiangsu), Emperor Gaozu briefly commissioned Li Shimin to attack Fu, but soon cancelled the order and sent Li Shimin's cousin Li Xiaogong the Prince of Zhao Commandery instead.

In 624, when Li Jiancheng was found to have, against regulations, tried to add soldiers to his guard corps, Emperor Gaozu was so angry that he put Li Jiancheng under arrest. In fear, Li Jiancheng's guard commander Yang Wen'gan rebelled. Emperor Gaozu sent Li Shimin against Yang, offering to make him crown prince after he returned. After Li Shimin left, however, Feng Deyi (now a chancellor), Li Yuanji, and the concubines all spoke on Li Jiancheng's behalf, and after Li Shimin returned, Emperor Gaozu did not depose Li Jiancheng, but instead blamed the discord between him and Li Shimin on Li Jiancheng's staff members Wang Gui and Wei Ting and Li Shimin's staff member Du Yan, exiling them to Xi Prefecture (, roughly modern Liangshan Yi Autonomous Prefecture, Sichuan).

Later that year, Emperor Gaozu, troubled by repeated Göktürk incursions, seriously considered burning Chang'an to the ground and moving the capital to Fancheng, a suggestion that Li Jiancheng, Li Yuanji, and Pei Ji agreed with. Li Shimin opposed, however, and the plan was not carried out. Meanwhile, Li Shimin himself was sending his confidants to Luoyang to build up personal control of the army there. After an incident in which Li Shimin suffered a severe case of food poisoning after feasting at Li Jiancheng's palace—an event that both Emperor Gaozu and Li Shimin apparently interpreted as an assassination attempt—Emperor Gaozu considered sending Li Shimin to guard Luoyang to prevent further conflict, but Li Jiancheng and Li Yuanji, after consulting each other, believed that this would only give Li Shimin an opportunity to build up his personal power there, and therefore opposed it. Emperor Gaozu therefore did not carry out the plan. Meanwhile, the rivalry continued. Traditional historical accounts also indicated that at one point, when Li Shimin visited Li Yuanji's mansion, Li Yuanji wanted to assassinate Li Shimin, but Li Jiancheng, who could not resolve to kill a brother, stopped the plot. There was yet another incident in which Li Jiancheng, knowing that a horse threw its rider easily, had Li Shimin ride it, causing Li Shimin to fall off from it several times.

By 626, Li Shimin was fearful that he would be killed by Li Jiancheng, and his staff members Fang Xuanling, Du Ruhui, and Zhangsun Wuji were repeatedly encouraging Li Shimin to attack Li Jiancheng and Li Yuanji first—while Wei Zheng was encouraging Li Jiancheng to attack Li Shimin first. Li Jiancheng persuaded Emperor Gaozu to remove Fang and Du, as well as Li Shimin's trusted guard generals Yuchi Jingde and Cheng Zhijie, from Li Shimin's staff. Zhangsun Wuji, who remained on Li Shimin's staff, continued to try to persuade Li Shimin to attack first.

In summer 626, the Göktürks were making another attack, and under Li Jiancheng's suggestion, Emperor Gaozu, instead of sending Li Shimin to resist the Göktürks as he first was inclined, decided to send Li Yuanji instead. Li Yuanji was given command of much of the army previously under Li Shimin's control, further troubling Li Shimin, who believed that with the army in Li Yuanji's hands, he would be unable to resist an attack. Li Shimin had Yuchi summon Fang and Du back to his mansion secretly, and then on one night submitted an accusation to Emperor Gaozu that Li Jiancheng and Li Yuanji were committing adultery with Emperor Gaozu's concubines. Emperor Gaozu, in response, issued summonses to Li Jiancheng and Li Yuanji for the next morning, convening the senior officials Pei Ji, Xiao Yu, and Chen Shuda to examine Li Shimin's accusations. As Li Jiancheng and Li Yuanji approached the central gate leading to Emperor Gaozu's palace, Xuanwu Gate, Li Shimin carried out the ambush he had set. He personally fired an arrow that killed Li Jiancheng. Subsequently, Yuchi Jingde killed Li Yuanji. Li Shimin's forces entered the palace and, under the intimidation of Li Shimin's forces, Emperor Gaozu agreed to create Li Shimin crown prince. Li Jiancheng's and Li Yuanji's sons were killed, and Li Shimin took Li Yuanji's wife Princess Yang as a concubine. Two months later, with Li Shimin firmly in control of power, Emperor Gaozu yielded the throne to him (as Emperor Taizong).

As emperor

Early reign (626–633)

One of the first actions that Emperor Taizong carried out as emperor was releasing a number of ladies in waiting from the palace and returning them to their homes, so that they could be married. He made his wife Princess Zhangsun the empress, and their oldest son Li Chengqian the crown prince.

Emperor Taizong also immediately faced a crisis, as the Eastern Turkic leader Illig Qaghan (Ashina Duobi), along with his nephew the subordinate Tuli Khan Ashina Shibobi (阿史那什鉢苾), launched a major incursion toward Chang'an, and just 19 days after Emperor Taizong took the throne, the two khans were just across the Wei River from Chang'an. Emperor Taizong, accompanied by Gao Shilian and Fang Xuanling, was forced to meet Ashina Duobi across the river and personally negotiate peace terms, including tributes to Eastern Turks, before Ashina Duobi withdrew.

Late in 626, Emperor Taizong ranked the contributors to Tang rule and granted them titles and fiefs, naming among the first rank of contributors Zhangsun Wuji, Fang Xuanling, Du Ruhui, Yuchi Jingde, and Hou Junji. When Li Shentong, as his distant uncle, objected to being ranked under Fang and Du, Emperor Taizong personally explained how Fang and Du's strategies allowed him to be successful, and this managed to get the other objectors to quiet down, as Emperor Taizong was even willing to rank low such an honored individual as Li Shentong. Emperor Taizong also buried Li Jiancheng and Li Yuanji with honors due imperial princes and had their staff members attend the funeral processions. Meanwhile, he appeared to begin to reshuffle government further—which he had already begun after being created crown prince—by dismissing his father's trusted advisors Xiao Yu and Chen Shuda, making his own trusted advisors chancellors. (Xiao, however, was soon restored to being chancellor, although his career during Emperor Taizong's reign would see repeated dismissals and repeated restorations.) However, he also began to greatly pay attention to the officials' submissions and their criticism of imperial governance, making changes where he saw needed. He also particularly began to trust Wei Zheng, accepting much advice from Wei as far as his personal conduct was concerned. He was also willing to demote his own trusted advisors, as he demoted Gao Shilian after finding that Gao had held back submissions from his deputy Wang Gui. Viewing Sui's Emperor Yang as a negative example, he frequently solicited criticism, rewarding those officials willing to offer them, particularly Wei and Wang Gui. His openness to opposing ideas was also evident in his attempt to reconcile traditional Taoist religion and Buddhism, as demonstrated in his Emperor's Preface to the Sacred Teachings, and Emperor Taizong was at least a nominal Taoist.

Li Yis Rebellion

Also in 627, the general Li Yi the Prince of Yan—a late-Sui warlord who later submitted to Tang, who associated with Li Jiancheng—fearing that Emperor Taizong would eventually take action against him, rebelled at Bin Prefecture (豳州, in modern Xianyang), but was quickly crushed by the official Yang Ji and killed in flight. Later that year, when Emperor Gaozu's cousin Li Youliang (李幼良) the Prince of Changle, the commandant at Liang Prefecture (, roughly modern Wuwei, Gansu), was accused of allowing his staff to oppress the people and to trade with Qiang and Xiongnu tribesmen, Emperor Taizong sent the chancellor Yuwen Shiji (Yuwen Huaji's brother) to investigate, and in fear, Li Youliang's staff members plotted to hold him hostage and rebel. When this was discovered, Emperor Taizong forced Li Youliang to commit suicide. Late in the year, Wang Junkuo (王君廓), the commandant at You Prefecture (幽州, roughly modern Beijing), also rebelled, but was defeated quickly and killed in flight. However, although there were also reports that Feng Ang, a warlord in the Lingnan region, was rebelling, Emperor Taizong, at Wei's suggestion, sent messengers to comfort Feng, and Feng submitted.

Also in 627, Emperor Taizong, seeing that there were too many prefectures and counties, consolidated and merged many of them, and further created another level of local political organization above prefectures—the circuit (道 dào)—dividing his state into 10 circuits.

Campaign against the Eastern Turks

In 628, with Ashina Duobi and Ashina Shibobi having a falling out, Ashina Shibobi submitted to Emperor Taizong, as did the chieftains of Khitan tribes, who had previously submitted to the Eastern Turks. With their khaganate in turmoil, Ashina Duobi was no longer able to protect the last late-Sui rebel ruler who alone remained standing against Tang pressure—Liang Shidu the Emperor of Liang, and in summer 628, with the Tang generals Chai Shao and Xue Wanjun sieging the Liang capital Shuofang (in modern Yulin, Shaanxi), Liang Shidu's cousin Liang Luoren (梁洛仁) killed Liang Shidu and surrendered, finally uniting China. With the Eastern Turkic Khaganate weakened, their vassal Xueyantuo also broke away and formed its own khanate, and Emperor Taizong entered into an alliance with Xueyantuo's leader Yinan, creating Yinan the Zhenzhupiqie Khan (or Zhenzhu Khan in short).

In late 629, believing the time ripe for a major attack on the Eastern Turks, Emperor Taizong commissioned the general Li Jing with overall command of a multi-pronged army, assisted by the generals Li Shiji, Li Daozong, Chai Shao, Xue Wanche (, Xue Wanjun's brother) and Su Dingfang, attacking the Eastern Turks at multiple points. The army was successful in its attacks, forcing Ashina Duobi to flee, and by late spring 630, Ashina Duobi had been captured, and Eastern-Turkic chieftains all submitted to Tang. Emperor Taizong spared Ashina Duobi but detained him at Chang'an, and he considered what to do with the Eastern Turks.

The main opposing views were from the chancellors Wen Yanbo (who advocated leaving the Turks within China's borders to serve as a defense perimeter) and Wei (who advocated leaving them outside the borders). Emperor Taizong accepted Wen's suggestion and established a number of prefectures to accommodate the Turks, leaving them governed by their chieftains without creating a new khan to govern them.

In 631, Emperor Taizong established a feudal scheme, where the contributors to his reign were given, in addition to their current posts, additional posts as prefectural governors, to be passed on to their descendants. Soon, however, receiving much opposition to the plan, the strongest of which came from Zhangsun Wuji, Emperor Taizong cancelled the scheme.

After the conquest of the Eastern Turkic Khaganate, Emperor Taizong's officials repeatedly requested that he carry out sacrifices to heaven and earth at Mount Tai, and Emperor Taizong, while at times tempted by the proposal, was repeatedly dissuaded from doing so by Wei, who pointed out the expenses and the labors that would be imposed on the people as a result, and also that this would open China's borders to attack.

Middle reign (634–641)

In 634, Emperor Taizong sent 13 high level officials, including Li Jing and Xiao Yu, to examine the circuits to see whether the local officials were capable, to find out whether the people were suffering, to comfort the poor, and to select capable people to serve in civil service. (Li Jing initially recommended Wei Zheng, but Emperor Taizong declined sending Wei, stating that Wei needed to stay to point out his faults and that he could not afford to have Wei away even for a single day.)

Campaign against Tuyuhun

Around this time, Tang was having increasing conflicts with Tuyuhun, whose Busabo Khan Murong Fuyun, under instigation by his strategist the Prince of Tianzhu, had been repeatedly attacking Tang prefectures on the borders. At one point, Murong Fuyun sought to have a Tang princess marry his son the Prince of Zun, but the marriage negotiations broke down over Emperor Taizong's insistence that the Prince of Zun come to Chang'an for the wedding. In summer 634, Emperor Taizong had the generals Duan Zhixuan and Fan Xing lead forces against Tuyuhun, but with Tuyuhun's forces highly mobile and avoiding direct confrontation, Duan, while not defeated, could not make major gains. Once Duan withdrew, Tuyuhun resumed hostilities. In winter 634, with the Tibetan king Songtsän Gampo making overtures to marry a Tang princess as well, Emperor Taizong sent the emissary Feng Dexia to Tibet with an eye toward an alliance against Tuyuhun. In winter 634, he commissioned Li Jing, assisted by the other generals Hou Junji, Xue Wanjun, Xue Wanche, Qibi Heli, Li Daozong, Li Daliang, Li Daoyan, and Gao Zengsheng (高甑生), to attack Tuyuhun. In 635, Li Jing's forces crushed Tuyuhun forces. Murong Fuyun was killed by his own subordinates, and his son Murong Shun killed the Prince of Tianzhu and surrendered. Emperor Taizong created Murong Shun the new khan, although Murong Shun was soon assassinated. Emperor Taizong then created Murong Shun's son Murong Nuohebo as the new khan.

Also in 635, Emperor Gaozu died, and Emperor Taizong, observing a mourning period, briefly had Li Chengqian serve as regent, and after he resumed his authorities less than two months later, he still authorized Li Chengqian to thereafter rule on minor matters.

In spring 636, Emperor Taizong commissioned his brothers and sons as commandants and changed their titles in accordance with the commands that they received, sending them to their posts—with the exception of his son Li Tai the Prince of Wei, who by this point was beginning to be highly favored by him. He further allowed Li Tai to engage literary men to serve as his assistants, as Li Tai favored literature. From this point on, Li Tai would be so favored that there began to be talks that Emperor Taizong might let him displace Li Chengqian, whose favors began to wane.

In fall 636, Empress Zhangsun died. Emperor Taizong mourned her bitterly and personally wrote the text of her monument.

In summer 637, Emperor Taizong recreated the feudal scheme that he had considered and abandoned in 631, creating 35 hereditary prefect posts. (By 639, however, the system was again abandoned after much opposition.)

Treatment of Noble Clans

Sometime before 638, Emperor Taizong, disgusted with the traditional noble clans of Cui, Lu, Li, and Zheng and believing that they were abusing their highly honored names, commissioned Gao Shilian, Wei Ting, Linghu Defen, and Cen Wenben to compile a work later to be known as the Records of Clans (氏族志), with the intent of dividing the clans into nine classes based on their past contributions, good deeds, and ill deeds. In an initial draft that Gao submitted, he nevertheless ranked the branch of the Cui clan that the official Cui Min'gan belonged to as the highest, a decision that Emperor Taizong rebuked, as he pointed out that Gao was merely again looking at tradition and not the recent contributions. He therefore personally intervened in revising the work, reducing Cui's clan to the third class.

Tibetan attack on Songzhou

In fall 638, Tibet's Songtsän Gampo, displeased that Emperor Taizong had declined to give him a Tang princess in marriage and believing that Murong Nuohebo had persuaded Emperor Taizong to decline the marriage proposal, launched a major attack with forces of 200,000 on Tuyuhun and then on several Tang prefectures, putting Song Prefecture (松州, roughly modern Ngawa Tibetan and Qiang Autonomous Prefecture, Sichuan) under siege. Emperor Taizong commissioned Hou Junji, assisted by Zhishi Sili, Niu Jinda, and Liu Jian, of a total of force of 50,000 to counterattack, and Niu, who commanded the forward forces, defeated Tibetan forces at Song Prefecture. Songsän Gampo withdrew and sued for peace, but still sought to marry a Tang princess. Emperor Taizong agreed this time.

Also in 638, believing that Xueyantuo was growing increasingly strong and difficult to control, Emperor Taizong granted Yinan's sons Bazhuo and Jialibi both lesser khan titles, to try to create dissensions between them.

In summer 639, Ashina Jiesheshuai, the younger brother of Ashina Shibobi, whom Emperor Taizong did not favor and gave little recognition to, formed a conspiracy with Ashina Shibobi's son Ashina Hexiangu to assassinate Emperor Taizong. They had planned to wait for Li Zhi the Prince of Jin to depart from the palace in the morning and use that opportunity to attack the palace. On the day they planned, however, Li Zhi did not leave the palace, and Ashina Jiesheshuai attacked anyway but was quickly defeated, captured, and executed. After this incident, however, the officials began advocating sending the Turks away from the heart of the state. In fall 639, Emperor Taizong created a Turkish prince who had served him faithfully, Li Simo (né Ashina Simo) as the khan of a newly recreated Eastern Turkic state (as Qilibi Khan), giving him all of the Turks and Xiongnu who had surrendered as his subordinates, to be settled north of the Great Wall and the Yellow River. However, the Turks were fearful of Xueyantuo and initially refused to head to their new ___location. Emperor Taizong issued an edict to Yinan that he and Li Simo keep their peace and not attack each other, and after receiving from Yinan the assurance that he would not attack, the Turks advanced to the new ___location.

Campaign against Western Turks

Taizong began a series of campaigns against the Western Turks (Xitujue) and their allies, the oasis states of the Tarim Basin, around 640. These hostilities between the Western Turks and Tang would continue until the defeat and conquest of the Western Turks in 657 under Taizong's successor, Gaozong. The kingdoms of Shule and Khotan surrendered to the Chinese in 632, as did the kingdom of Yarkand in 635. Qu Wentai (麴文泰), the king of Gaochang, who had previously been submissive to Tang, had become increasingly hostile to Tang, allying with the Western Turks. In 640, Emperor Taizong commissioned Hou Junji, assisted by Xue Wanjun, to launch a major attack on Gaochang. As they approached Gaochang, Qu Wentai died in fear and was succeeded by his son Qu Zhisheng (麴智盛). Qu Zhisheng offered to submit, but Hou demanded a surrender, which Qu Zhisheng refused. However, Hou put Gaochang under siege, and with aid from the Western Turks not arriving, Qu Zhisheng surrendered. Wei Zheng suggested that Emperor Taizong allow Qu Zhisheng to remain king, pointing out that the monetary and human costs would be high to keep a permanent garrison at Gaochang, but Emperor Taizong disagreed, and he converted Gaochang into two prefectures and annexed it into his state.

In winter 640, Songsän Gampo sent his prime minister Gar Tongtsen Yülsung ("Lu Dongzan" in Chinese) as an emissary to Tang, offering tributes and again requesting marriage. Emperor Taizong created a daughter of a clansman as the Princess Wencheng, and in 641 sent Li Daozong to accompany Princess Wencheng to Tibet to preside over the wedding.

In winter 641, believing that Emperor Taizong was about to carry out sacrifices to heaven and earth at Mount Tai and would be unable to aid the Eastern Turks, Yinan launched a major attack on them, commanded by his son Dadu (大度). Li Simo was forced to retreat inside the Great Wall. Emperor Taizong commissioned Li Shiji, assisted by Zhang Jian, Li Daliang, Zhang Shigui, and Li Xiyu, to attack Xueyantuo. Li Shiji soon defeated Dadu at Nuozhen River (, flowing through modern Baotou, Inner Mongolia), and Dadu fled.

Late reign (642–649)

By 642, it was clear that Li Tai had ambitions on replacing his brother Li Chengqian, and the governmental officials began to be divided into pro-Li Chengqian and pro-Li Tai factions. After urging by Wei Zheng and Chu Suiliang to take actions that would clarify that Li Chengqian's position was secure, Emperor Taizong attempted to do so by making repeated statements to that effect, but his continued favoring of Li Tai led to continued speculation among officials.

Also by 642, Xueyantuo had posed a sufficiently serious threat (albeit still formally submissive) that Emperor Taizong saw two alternatives—destroying it by force or forming into a heqin relationship by marrying one of his daughters to Yinan. This particularly became an issue after the Tang general Qibi Heli (契苾何力), the chieftain of the Qibi Tribe, was kidnapped by his own subordinates and taken to Xueyantuo. In order to ransom Qibi, Emperor Taizong made a promise to eventually give his daughter Princess Xinxing to Yinan in marriage, and Yinan released Qibi.

In the winter 642, an event took place in Goguryeo that would eventually precipitate wars between Tang and Goguryeo. According to Chinese accounts King Yeongnyu, the king of Goguryeo, was apprehensive about his general Yeon Gaesomun and was plotting with his other officials to kill Yeon. When Yeon received the news, he started a coup and killed the king and the high level officials. He declared King Yeongnyu's nephew Go Jang (King Bojang) king, while taking power himself with the title of Dae Mangniji (, Generalissimo). When Emperor Taizong received the news, there were suggestions that an attack be launched against Goguryeo, suggestions that Emperor Taizong initially declined.

In spring 643, Wei died, and Emperor Taizong mourned him bitterly, authoring Wei's monument himself and, prior to Wei's death, promising to give his daughter Princess Hengshan in marriage to Wei's son Wei Shuyu (魏叔玉). Later in spring, Emperor Taizong commissioned 24 portraits at Lingyan Pavilion to commemorate the 24 great contributors to his reign.

Contacts with the Byzantine Empire

The Old Book of Tang and New Book of Tang mention several embassies made by Fu lin (; i.e. the Byzantine Empire), which they equated with Daqin (which may refer to the Roman Empire or Middle East), beginning in 643 with an embassy sent by the king Boduoli (波多力, i.e. Constans II Pogonatos) to Emperor Taizong, bearing gifts such as red glass and green gemstones. These histories also provided cursory descriptions of Constantinople and its walls, as well as how it was besieged by Da shi (大食; the Arabs of the Umayyad Caliphate) and their commander "Mo-yi" (摩拽; i.e. Muawiyah I, governor of Syria before becoming caliph), who forced the Byzantines to pay tribute. Henry Yule highlights the fact that Yazdegerd III (r. 632–651), last ruler of the Sasanian Empire, sent diplomats to China for securing aid from Emperor Taizong (considered the suzerain over Ferghana in Central Asia) during the loss of the Persian heartland to the Islamic Rashidun Caliphate, which may have also prompted the Byzantines to send envoys to China amid their recent loss of Syria to the Muslims. Tang Chinese sources also recorded how Sassanid prince Peroz III (636–679) fled to Tang China following the conquest of Persia by the growing Islamic caliphate.

The expansion of China's power into Central Asia under Emperor Taizong seems to have been noticed in the West. Theophylact Simocatta, a Byzantine Greek historian during the reign of Heraclius (r. 610–641), wrote that Taugast (or Taugas; Old Turkic: Tabghach, from Tuoba, the Xianbei clan of Northern Wei), was a great eastern empire in the Far East that ruled over Turkic people, with a capital city roughly 1,500 miles northeast from India that he called Khubdan (from the Turkic word Khumdan, meaning, Chang'an), where idolatry was practiced but the people were wise and lived by just laws. He depicted the Chinese empire as being divided by a great river (i.e. the Yangzi) that served as the boundary between two rival states at war, yet during the reign of Byzantine Emperor Maurice (582–602 AD) the northerners wearing "black coats" conquered the "red coats" of the south (black being a distinctive color worn by the people of Shaanxi, ___location of the Sui capital Sui Chang'an, according to the 16th-century Persian traveler Hajji Mahomed, or Chaggi Memet). This account may correspond to the conquest of the Chen dynasty and reunification of China by Emperor Wen of Sui (r. 581–604). Simocatta names their ruler as Taisson, which he claimed meant Son of God, either correlating to the Chinese Tianzi (i.e. Son of Heaven) or even the name of the contemporary ruler Emperor Taizong.

Succession dispute

Also in 643, Emperor Taizong would see major turmoil among his own closest family. In spring 643, his son Li You (李佑) the Prince of Qi, angry over restrictions that his secretary general Quan Wanji had often placed on him, killed Quan and declared a rebellion. Emperor Taizong sent Li Shiji against Li You, but before Li Shiji could engage Li You, Li You was captured by his own subordinate Du Xingmin (杜行敏) and delivered to Chang'an, where Emperor Taizong ordered him to commit suicide and executed 44 of his associates.

The death of Li You drew out news of another plot. Li Chengqian, who had been fearful that Emperor Taizong would eventually remove him and replace him with Li Tai, had begun to conspire with Hou Junji, Li Yuanchang (李元昌) the Prince of Han (Emperor Taizong's brother), the general Li Anyan, and his brothers-in-law Zhao Jie and Du He (杜荷, Du Ruhui's son) to overthrow Emperor Taizong. During the investigations in the aftermaths of Li You's rebellion, one of the co-conspirators, Li Chengqian's guard Gegan Chengji, was implicated by association, and in order to save himself, he revealed Li Chengqian's plot. Emperor Taizong was shocked by the news, and he appointed Zhangsun Wuji, Fang Xuanling, Xiao Yu, and Li Shiji, along with the officials in charge of the supreme court and the legislative and examination bureaus of the government to carry out a joint investigation. At the suggestion of the mid-level official Lai Ji, Emperor Taizong deposed, but did not kill, Li Chengqian, while ordering Li Yuanchang to commit suicide and executing Hou Junji, Li Anyan, Zhao, and Du.

Taizong's eldest son Li Chengqian chose to speak Turkic, dress in Turkic clothes and even set up a tent in his residence in imitation of a Turkic khan. Taizong removed him from the position of heir apparent and chose as his successor Li Zhi, who embraced Han Chinese cultural heritage.

After Li Chengqian was deposed, Emperor Taizong briefly promised Li Tai that he would be made crown prince. However, as the investigations continued, Emperor Taizong came to the belief that Li Chengqian's downfall was driven by Li Tai's machinations, and therefore resolved to depose Li Tai as well. At Zhangsun's suggestion, Emperor Taizong created a younger son, Li Zhi the Prince of Jin (who, like Li Chengqian and Li Tai, were born of Empress Zhangsun), crown prince, who was considered kinder and gentler, while exiling Li Chengqian and Li Tai. However, starting later that year, Emperor Taizong began to doubt whether Li Zhi's personality was sufficiently strong to serve as emperor, and he toyed with the idea of making another son, Li Ke the Prince of Wu, a son of his concubine Consort Yang (Emperor Yang of Sui's daughter), crown prince, but did not do so due to strong opposition by Zhangsun Wuji.

Meanwhile, coming to the belief that he made an ill-advised promise to Yinan to give him Princess Xinxing in marriage, Emperor Taizong demanded a large amount of bride price – 50,000 horses, 10,000 cows and camels, and 100,000 sheep—a price that Yinan agreed to, but could not immediately collect and deliver. Emperor Taizong used it as an excuse to cancel the marriage agreement. Meanwhile, as Wei Zheng had, prior to his death, recommended Hou Junji and Li Chengqian's staff member Du Zhenglun as chancellors, Emperor Taizong came to suspect that Wei was part of the plot as well. He destroyed the monument he had authored for Wei and cancelled the betrothal between Wei Shuyu and Princess Hengshan.

Campaign against the Karasahr

In 644, with Yanqi's king Long Tuqizhi, who had assisted the Tang campaign to conquer Gaochang, turning against Tang and allying with the Western Turks, Emperor Taizong sent the general Guo Xiaoke (郭孝恪), the commandant at Anxi (安西, i.e., Gaochang) to launch a surprise attack on Yanqi. Guo caught Long Tuqizhi by surprise and captured him, making his brother Long Lipozhun regent. (The Western Turkic viceroy Ashina Quli (阿史那屈利) subsequently captured Long Lipozhun and briefly occupied Yanqi, although he then, not wanting a direct confrontation with Tang, withdrew, and the Yanqi nobles made Long Tuqizhi's cousin Long Xuepoanazhi king.)

Goguryeo-Tang War

Also in 644, with Goguryeo attacking Silla and Silla requesting aid, Emperor Taizong decided to prepare for a campaign to conquer Goguryeo. He arrested the emissaries that Yeon sent to the Tang court, accusing them of disloyalty to King Yeongnyu. By winter 644, the mobilization was in full force. (Apparently because of Tang's preparation to attack Goguryeo, however, the reconstituted Eastern Turkic people, fearing an attack from Xueyantuo at a time that Tang would be ill-equipped to assist, panicked and abandoned their khan Li Simo, fleeing into Tang territory. Emperor Taizong reabsorbed the Eastern Turks into Tang, while making Li Simo a general in his army.)

In spring 645, Emperor Taizong departed from Luoyang and led the troops northeast, behind a vanguard of 60,000 commanded by Li Shiji and Li Daozong. At the same time, Zhang Liang led the other 40,000 from sea. By summer 645, Tang forces had captured Yodong Fortress (, in modern Liaoyang, Liaoning), and headed southeast toward the Goguryeo capital Pyongyang. Emperor Taizong personally led about 30,000 Tang and tribal forces and defeated a 150,000 force commanded by two Gogureyo generals and then put Ansi (安市, in modern Anshan, Liaoning) fortress under siege.

However, the capable defense put up by Ansi's commanding general stymied Tang forces and, in late fall, after suffering some casualties, with winter fast approaching and his food supplies running out, Emperor Taizong withdrew. He much regretted launching the campaign and made the comment, "If Wei Zheng were still alive, he would never have let me launch this campaign." He reerected the monument he authored for Wei and summoned Wei's wife and children to meet him, treating them well.

Campaign against Xueyantuo and conquest of the Kucha

Meanwhile, in the aftermaths of the Goguryeo campaign, Xueyantuo's Duomi Khan Bazhuo (son of Yinan, who had died earlier in 645) launched attacks against Tang's border prefectures, with largely inconclusive results. In spring 646, the Tang generals Qiao Shiwang and Zhishi Sili counterattacked, defeating Bazhuo's forces, causing him to flee. His vassals Huige, Pugu (仆骨), and Tongluo tribes took the opportunity to rebel and attack him. Hearing this, Emperor Taizong launched a major attack, commanded by Li Daozong, Ashina She'er, Zhishi Sili, Qibi Heli, Xue Wanche, and Zhang Jian, against Xueyantuo. With Xueyantuo under attack from multiple sides, Bazhuo was killed by Huige forces, and the remaining Xueyantuo people fled and supported Bazhuo's cousin Duomozhi as Yitewushi Khan, but soon offered to submit to Tang. Emperor Taizong sent Li Shiji toward Duomozhi's ___location, with the direction to either accept his submission or destroy him. Duomozhi surrendered and was taken to Chang'an, ending Xueyantuo's rule over the region. The other tribes formerly submissive to Xueyantuo offered Emperor Taizong the title of "Heavenly Khan" and thereafter largely became submissive to Tang. Tang nominally established seven command posts and six prefectures over the region. (Huige's khan Yaoluoge Tumidu, while submissive to Tang, for some time tried to take control over the region himself, but was subsequently assassinated in 648, and there would be no other organized attempt by Huige to take over the region until for about another century.)

After the victory over Xueyantuo, Emperor Taizong again turned his attention toward to Goguryeo, cutting off relations once more and considering another campaign. Under suggestions by some of his officials, he decided to launch harassment campaigns against Goguryeo's northern region on a yearly basis, to weaken Goguryeo gradually. The first of these campaigns was launched in spring 647, with Li Shiji and Niu Jinda in command, and would reoccur. All this was in preparation of another campaign in 649 with forces totaling 300,000, but Taizong died before this campaign and the campaign was stalled into Gaozong's reign.

In 648, Emperor Taizong launched another campaign, commanded by Ashina She'er, aimed at Qiuzi, but first attacking Yanqi and killing Long Xuepoanazhi and replacing him with his cousin Long Xiannazhun. Ashina She'er advanced on Qiuzi and captured its king Bai Helibushibi, making his brother king instead.

Death

By summer of 649, Emperor Taizong was seriously ill—with some believing that his illness was caused by the medicine he was administered by Buddhists or his taking of pills given to him by alchemists. Believing Li Shiji to be capable but fearing that he would not be submissive to Li Zhi, he demoted Li Shiji out of the capital to be the commandant at remote Die Prefecture (叠州, roughly modern Gannan Tibetan Autonomous Prefecture, Gansu), with instructions to Li Zhi that if Li Shiji hesitated, to execute him immediately, and if he did not, to recall him after Emperor Taizong's death and make him chancellor. Li Shiji, when receiving the order and realizing that his life was at stake, immediately departed for Die Prefecture. (After Emperor Taizong's death, Li Zhi would indeed recall Li Shiji and make him chancellor.) Soon thereafter, Emperor Taizong, after entrusting Li Zhi to Zhangsun Wuji and Chu Suiliang, died at his summer palace Cuiwei Palace. His death was initially kept a secret, and three days later, after his casket had been returned to Chang'an, his death was announced, and Li Zhi took the throne as Emperor Gaozong.

Religious views

Emperor Taizong stated he believed in the Tao, although his vision of it was a greatly syncretized version. He believed in Jesus as a Taoist hero and Confucian sage, and incorporated elements of Taoism, Confucianism, Buddhism, Zoroastrianism, Judaism, Islam, Syriac Christianity (as well as the Church of the East, which was a major institution in that branch of Christianity), and other Middle Eastern religions in his personal religion that was enforced by laws that demanded his subjects practice tolerance.

Monuments

After consolidating the Tang Empire, Emperor Taizong ordered six large stone panels, known as Zhaoling Liujun, to be carved with the portraits of his favorite horses. These were the horses he had ridden in overcoming his rivals and securing the borders of the country.

Emperor Taizong further composed laudatory poems for each of the six horses depicted in the stone reliefs. Constructed between 636 and 649 CE, the stone reliefs "exemplify the beauty of early Tang sculpture; the images are realistic yet powerful, created with simplicity and matured craftsmanship."

After Taizong's death, the monuments were situated along the east and west sides of the "spirit path" at the North Gate of the tomb complex named Zhaoling or Zhao Mausoleum. The six stone horse reliefs remained at the Mausoleum until the early twentieth century, when four were removed to the Beilin Museum in Xi'an, China and two were sold and subsequently donated to the Penn Museum in Philadelphia in 1921.

Era name

• Zhenguan (贞观 zhēnguàn ) 627–649

Chancellors during reign

Family

Consorts and issue

• Empress Wende, of the Zhangsun clan of Henan (文德皇后 河南长孙氏／长孙氏; 601–636)

　• Li Chengqian, Prince Min of Hengshan (恒山愍王 李承乾／恒山愍王 李承亁; 618–645), 1st son

　• Li Tai, Prince Gong of Pu (濮恭王 李泰; 620–653), 4th son

　• Princess Changle (长乐公主／长乐公主; 621–643), personal name Lizhi (丽质／丽质), 5th daughter

　　• Married Zhangsun Chong of Henan (河南 长孙冲／长孙冲), a son of Zhangsun Wuji, in 633, and had issue (one son)

　• Li Zhi, Gaozong (高宗 李治; 628–683), 9th son

　• Princess Chengyang (城阳公主／城阳公主; d. 671), 16th daughter

　　• Married Du He of Jingzhao, Duke Xiangyang (京兆 杜荷; 616–643), a son of Du Ruhui

　　• Married Xue Guan of Hedong (河东 薛瓘／河东 薛瓘) in 643, and had issue (two sons)

　• Princess Jinyang (晋阳公主/晋阳公主; 633–644), personal name Mingda (明达), 19th daughter

　• Princess Xincheng (新城公主; 634–663), 21st daughter

　　• Married Zhangsun Quan of Henan (河南 长孙诠/长孙诠; 636–659) in 649

　　• Married Wei Zhengju of Jingzhao (京兆 韦正矩／韦正矩; d. 663) in 660

• Noble Consort, of the Wei clan (贵妃 京兆韦氏／贵妃 京兆韦氏; 597–665), personal name Gui (圭)

　• Princess Linchuan (临川公主／临川公主; 624–682), personal name Mengjiang (孟姜), 10th daughter

　　• Married Zhou Daowu of Runan, Duke Qiao (汝南 周道务／周道务), and had issue (three sons, two daughters)

　• Li Shen, Prince of Ji (纪王 李慎／纪王 李慎; d. 689), 10th son

• Noble Consort, of the Yang clan (贵妃 杨氏／贵妃 杨氏)

　• Li Fu, Prince of Zhao (赵王 李福／赵王 李福; 634–670), 13th son

• Consort, of the Yang clan (妃 杨氏／杨氏)

　• Li Ke, Prince of Wu (吴王 李恪; 619–653), 3rd son

　• Li Yin, Prince Dao of Shu (蜀悼王 李愔; d. 667), 6th son

• Consort, of the Yin clan (妃 阴氏/阴氏)

　• Li You, Prince of Qi (齐王 李佑／齐王 李佑; c.621–643), 5th son

• Virtuous Consort, of the Yan clan (德妃 燕氏; 609–671)

　• Li Zhen, Prince Jing of Yue (越敬王 李贞／李贞; 627–688), 8th son

　• Li Xiao, Prince Shang of Jiang (江殇王 李嚣／江殇王 李嚣; d. 632), 11th son

• Able Consort, of the Zheng clan (贤妃 郑氏／贤妃 郑氏)

• Able Consort, of the Xu clan (贤妃 徐氏／贤妃 徐氏; 627–650), personal name Hui (惠)

• Lady of Bright Countenance, of the Wei clan (昭容 韦氏／韦氏), personal name Nizi (尼子)

• Imperial Concubine, of a certain clan (下嫔某氏)

　• Princess Yuzhang (豫章公主), 6th daughter

　　• Married Tang Yishi (唐义识／唐义识), a son of Tang Jian, in 637, and had issue (one son)

• Lady of Beauty, of the Xiao clan (美人 萧氏)

• Lady of Talent, of the Wu clan; 624–705, personal name Mei (媚), known commonly as Wu Zetian

• Lady of Talent, of the Cui clan of Qinghe (才人 清河崔氏)

• Lady of Talent, of the Xiao clan (才人 萧氏)

• Princess Consort, of the Yang clan of Hongnong (王妃 弘农杨氏／弘农杨氏)

　• Li Ming, Prince Gong of Cao (曹恭王 李明; d. 682), 14th son

• Lady, of the Wang clan (王氏)

　• Li Yun, Prince of Jiang (蒋王 李恽/蒋王 李恽; d. 674), 7th son

• Lady, of the Gao clan (高氏)

• Unknown

　• Li Kuan, Prince Chu (楚王 李宽／李宽; b. 619), 2nd son

　• Li Jian, Prince Dai (代王 李简／李简; 631), 12th son

　• Princess Xiangcheng (襄城公主; d. 651), 1st daughter

　　• Married Xiao Rui of Lanling, Duke Song (兰陵 萧锐／兰陵 箫锐), a son of Xiao Yu

　• Princess Ru'nan (汝南公主; d. 636), 2nd daughter

　• Princess Nanping (南平公主; d. 650), d daughter

　　• Married Wang Jingzhi, Baron Nancheng (王敬直), the youngest son of Wang Gui, in 637

　　• Married Liu Xuanyi of Henan, Duke Yu (河南 刘玄意／刘玄意) in 643

　• Princess Sui'an (遂安公主; d. 651), 4th daughter

　　• Married Dou Kui of Henan, Baron Xindou (河南 窦逵／窦逵)

　　• Married Wang Dali (王大礼／王大礼; 613–669), and had issue (one son)

　• Princess Baling (巴陵公主; d. 653), 7th daughter

　　• Married Chai Lingwu, Duke Xiangyang (柴令武; d. 653), the second son of Chai Shao

　• Princess Pu'an (普安公主), 8th daughter

　　• Married Shi Renbiao, Duke Dou (史仁表)

　• Princess Dongyang (东阳公主／东阳公主; d. 701), 9th daughter

　　• Married Gao Lüxing of Bohai, Duke Shen (渤海 高履行), the first son of Gao Shilian

　• Princess Qinghe (清河公主; 624–664), personal name Jing (敬), courtesy name Dexian (德贤), 11th daughter

　　• Married Cheng Huailiang, Duke Dong'a (程怀亮/程怀亮), the second son of Cheng Zhijie, in 633

　• Princess Lanling (兰陵公主／兰陵公主; 628–659), personal name Shu (淑), courtesy name Lizhen (丽贞), 19th daughter

　　• Married Dou Huaizhe of Henan (河南 窦怀悊／窦怀哲) in 636, and had issue (one daughter)

　• Princess Jin'an (晋安公主／晋安公主), 13th daughter

　　• Married Wei Si'an of Jingzhao (京兆 韦思安／韦思安)

　　• Married Yang Renlu of Hongnong (弘农 杨仁辂／弘农 杨仁辂)

　• Princess Ankang (安康公主), 14th daughter

　　• Married Dugu Mou of Henan (河南 独孤谋／独孤谋) in 643

　• Princess Xinxing (新兴公主/新兴公主), 15th daughter

　　• Married Zhangsun Xi of Henan (河南 长孙曦／长孙曦)

　• Princess Gaoyang (高阳公主／高阳公主; d. 653), 17th daughter

　　• Married Fang Yi'ai of Qinghe (清河 房遗爱／房遗爱; d. 653), a son of Fang Xuanling, in 648

　• Princess Jinshan (金山公主), 18th daughter

　• Princess Changshan (常山公主), 20th daughter

Ancestry

Literary and other cultural references

• Emperor Taizong was the subject of a 64-chapter (in eight volumes) The Novel of the Prince of Qin of the Great Tang (大唐秦王词话 Datang Qin Wang Cihua) by Zhu Shenglin of the Ming dynasty. The novel is also known as The Biography of the Prince of Qin of the Tang Dynasty (唐秦王本传), Romance of Tang (唐传演义), and Romance of the Prince of Qin (秦王演义).

• Journey to the West details a fictional account of the origin of the Chinese door gods. Emperor Taizong asked his generals Qin Shubao and Yuchi Gong to stand guard outside his bedroom to protect him from a vengeful spirit.

Television/Cinema

• Hong Kong's TVB produced a television series about Li Shimin's adventure based on The Novel of the Prince of Qin of the Great Tang.

• The Foundation, a 1983 Hong Kong television series produced by TVB. It featured a young Li Shimin prominently as one of its three leading characters.

• Portrayed by Sean Lau in the 1987 TVB TV series The Grand Canal.

• Portrayed by Wilson Lam in 1993 Taiwan's TTV 54 episodes TV series Tang Taizong, Li Shimin.

• Portrayed by Peter Ho in the 2004 TV series The Prince of Qin, Li Shimin.

• Portrayed by Shen Xiaohai in the 2006 TV series Initiating Prosperity.

• Portrayed by Tang Guoqiang in the CCTV-1 TV series Carol of Zhenguan.

• Portrayed by Ma Yue in the 2006 BTV TV series The Rise of the Tang Empire.

• Portrayed by Seo In-seok and Lee Joo-hyeon in 2006–2007 SBS TV series Yeon Gaesomun.

• Portrayed by Song Yong-tae in the 2006–2007 KBS TV series Dae Jo Yeong.

• Portrayed by Yu Shaoqun in the 2012 Hunan TV TV series Heroes of Sui and Tang Dynasties.

• Portrayed by Yoon Seung-won in the 2012–2013 KBS1 TV series Dream of the Emperor.

• Portrayed by Du Chun in the 2013 Dragon TV TV series Heroes in Sui and Tang Dynasties.

• Portrayed by Zhang Fengyi in the 2014 Hunan Television TV series The Empress of China.

• Portrayed by Zheng Guo Lin in the 2014 TV series Heroes of Sui and Tang Dynasties 3 & 4.

• Portrayed by Winston Chao in the 2016 movie Xuanzang.

• Portrayed by Park Sung-woong in the 2018 Korean film The Great Battle.

• Portrayed by Geng Le in the 2021 Chinese TV series The Long Ballad 长歌行.

• Portrayed by Qin Junjie in the upcoming CCTV TV series Peace in Palace, Peace in Chang'An.

• Portrayed by Ma Yue in the TV series Ode to Daughter of Great Tang.

生平

早年经历

隋文帝开皇十七年十二月戊午日（598年1月28日），李世民出生于岐州武功县的庆善宫中（武功别馆），是当时担任隋朝岐州刺史的汉族官员李渊与窦氏所生的嫡次子。窦氏有四个儿子，一个女儿，按长幼顺序为：李建成、平阳昭公主、李世民、李玄霸、李元吉。由于李渊的母亲元贞皇后和李世民的母亲窦氏都既有汉人血统也有鲜卑血统，所以李世民父子是胡汉混合血统。

隋炀帝大业九年（613年），母亲在涿郡（治今北京市西南）病逝，鸿胪寺治礼郎高士廉看中了李世民，把外甥女长孙氏（登基后称长孙皇后）许配给李世民为妻。

大业十一年（615年），云定兴被授以左屯卫大将军，奉命援救在雁门关被突厥始毕可汗所率大军围困的隋炀帝。隋炀帝派人把诏书绑在木头上，放进汾河让诏书顺流而下，希望有人看到诏书前来救援。云定兴向各地招募愿意出征的军士，李世民那年只有十六岁，前去应募从军，被划归云定兴的帐下。云定兴手下只有两万新兵，且多是步兵。李世民向云定兴建议：突厥敢围困天子，是认定我们没有援军。不如我们把军队前后拉开，延绵数十里，让敌军白天看见旌旗招展，晚上听见钲鼓声声，误以为大军压境，如此才能不战而胜。若他们知我虚实，两兵相接，则胜败难料。云定兴采纳了李世民的疑兵之计攻突厥，突厥兵看到隋军浩浩荡荡络绎不绝，果然以为隋军大批救兵到，于是解围撤退。

隋大业十二年（616年），父亲李渊升任隋朝右骁卫将军。大业十三年（617年）正月，李渊又迁任太原郡留守，李世民也跟随到太原，李建成、李元吉和他们的异母弟李智云留在河东郡（今山西省永济市）。李世民时年十八。魏刀儿来攻太原，李渊率兵攻打，不幸深入敌阵，无法冲出重围。李世民以轻骑突围而进，张弓射敌，所向皆披靡，救李渊于万众之中。其后敌步兵又至，李渊与李世民又奋击，大破敌军。

晋阳起兵

隋朝各地反声四起，战火弥漫，民不聊生。李世民准备举义兵，于是抚恤百姓，礼遇士兵，散财养客，江湖人士、侠客义士，莫不愿效死力，为李唐起义兵做好充分准备。李世民在太原结纳长孙顺德、刘弘基、窦琮等人，与晋阳宫监裴寂和晋阳县令刘文静商议劝谏父亲李渊起兵反隋。东突厥支持的定杨可汗刘武周占领了太原附近汾阳宫，隋炀帝不满李渊和马邑郡太守王仁恭无力阻止东突厥入侵。隋炀帝要将李渊和王仁恭捉拿带到江都问罪，还没有成行，又将其赦免。

当时，有李氏取代杨氏的谶语，隋炀帝因为担心李浑的侄子李敏（炀帝的姐姐杨丽华的女婿）会应谶为帝，因此诛杀了李浑家族。李渊非常担心，在李世民、裴寂的鼓动下，决心起兵反隋。偷偷召唤李建成、李元吉从河东，女婿柴绍从长安前来太原。七月，李渊诛杀了隋炀帝派来监视他的郡丞王威、武牙郎将高君雅，接著打著「勤王定乱，迎回隋天子」的旗号，正式开始于晋阳县起兵，并且得到李氏宗族、姻亲的响应，是为晋阳起兵。李渊以李世民为敦煌郡公、右领军都督、统右三军。

李渊派刘文静出使东突厥得到了始毕可汗的支持，派李建成、李世民夺取西河郡。六月，正式起兵。李渊自为大将军，以长子李建成、次子李世民为左右大都督，以四子李元吉留守太原，进兵大兴城（长安）。

唐朝建立

七月，李世民随李渊出征，李渊在山西霍邑与隋将宋老生二万精兵相持于霍邑。恰值久雨粮尽，李渊与长史裴寂议论，不如暂且回太原，以后再图谋举事。李世民恳求李渊不要退却。李世民说：「原本兴立大义是为了拯救百姓，应当先攻入咸阳，号令天下；遇到小敌就回师，恐怕随从起义之人将会一朝解体。回去守太原一城之地，这不过是贼寇所为罢了，怎么能保全自己！」但是李渊不采纳，催促命令引军出发。李世民遂大哭于外，声闻帐中。李渊召问其故，李世民说：「现在部队凭藉正义而出动，前进、战斗就必定胜利，退回就一定会散夥。大家散夥于前，敌人趁机追击于后，死亡将顷刻而至，因此悲伤。」李渊醒悟而停止撤兵。

八月，雨停，引师取霍邑。李世民怕宋老生不出战，于是率领数名骑兵先到霍邑城下，拿著马鞭指点比划，好像围城样子，以激怒宋老生。宋老生果然发怒，开门出兵，背城列阵。李渊与李建成一起列阵于城东，李世民和柴绍列阵于城南。老生指挥兵士迅速前进，先逼近李渊，这时李建成忽然坠马，宋老生趁机进攻，李渊与李建成部队往后退却。李世民自城南高地率领两名骑兵急驰而下，冲断了宋老生部队，又领兵奋力进击，敌军大败，各扔掉兵器逃跑。宋老生退回到城门，城上闸门放下，宋老生手拉绳子想上城，被砍死，于是霍邑平定。

到了河东，关中豪杰争著奔赴参加义军。李世民请求进军入关，开永丰仓赈济百姓，收服群雄及众豪杰来谋取京都。李渊同意，从龙门渡黄河，先定渭北。关中有李世民的姐姐李三娘等人起兵响应。京都附近官民及豪杰绅士到军门请求献身报效义军者日以千计，扶老携幼，满于麾下。李世民收纳英俊，择才而用，远近闻者，皆来投靠。

唐军在泾阳宿营，有优秀兵士九万名，击破反隋盗寇胡人刘鹞子，兼并其部下，留下殷开山、刘弘基屯驻长安旧城。李世民自己带兵奔赴司竹，盗寇首领李仲文、何潘仁、向善志等都来相见，停留于阿城，获得兵士十三万人。长安父老送牛酒到营门劳军者不可胜数，李世民都加以慰问，然后送走他们，东西一概不收。军令严肃，秋毫无犯。接著与大军一起平定京城。

十一月，李渊攻克大兴，以代王杨侑为皇帝，尊隋炀帝杨广为太上皇，李渊自为大丞相、唐王。攻克隋大兴城后，李世民官拜京兆尹、受封秦国公。陇西的西秦霸王薛举不满李渊占据西京，派他的儿子薛仁杲来犯。李渊派李世民抵御薛仁杲，李世民在扶风击败薛仁杲，薛举暂时有投降李渊的念头，被谋士郝瑗劝阻。义宁二年（618年）春，隋朝东都洛阳被瓦岗军魏公李密围攻，李渊派李建成和李世民率军声称援助洛阳，想试探洛阳能否归顺自己。洛阳的官员拒绝了李渊的援助，李建成和李世民在此时不想与东都留守官员和李密争夺洛阳的控制权，于是撤军。三月初十（618年4月10日），李渊改封李世民为赵国公。三月，隋炀帝杨广在江都被宇文化及所杀，五月，李渊废黜杨侑，称帝，改国号为唐，定都大兴，易名长安，唐朝建立。李世民拜尚书令、晋为秦王。

统一中国

唐朝建立后，疆土只限于关中和河东一带，尚未完全统治全国，因此，李世民经常出征，最终统一中国。自武德元年起，李世民亲自参与四场大战役。

• 其一，破薛举，浅水原平定陇西薛仁杲（薛举之子），平定祖宗之地。

• 其二，败宋金刚、刘武周，收复并、汾失地，消灭北方地方军阀。

• 其三，在虎牢之战中，一举歼灭中原两大割据势力—河南王世充和河北窦建德集团，消除河北、河南的地方势力。

• 其四，重创窦建德馀部刘黑闼和山东的徐圆朗。

平定西秦

西秦薛举自立为秦帝，再次攻打唐朝，兵锋抵达泾州（今甘肃省泾川县） ，唐高祖派李世民为西讨元帅，抵御薛举。李世民深沟高垒，不肯与薛举交战，想要将薛举拖垮。但此时李世民身患疟疾，回后方修养。临走前，李世民令代为指挥军队的刘文静、殷开山不得擅自出兵。七月初九，刘文静、殷开山因轻视而出击薛举，被败于浅水原，唐军大败，伤亡十之五六。唐军被迫撤回长安，刘文静、殷开山被免职。薛举获胜后，听从郝瑗的建议，准备进攻长安。八月初九，薛举暴病而亡，其子薛仁杲继位。八月十七，唐高祖再派李世民为元帅，抵御薛仁杲。薛仁杲即位三个月后，唐军出击，在浅水原与薛仁杲的部将宗罗睺激战。结果，唐军击溃了宗罗睺的军队，然后袭击薛仁杲。薛仁杲被迫撤入高墌城，大批士兵降唐。薛仁杲只好降唐，李世民将他押送长安，被唐高祖处决。十二月初一，唐高祖任命李世民为太尉、使持节、陕东道大行台。

平定河东

武德二年（619年），刘武周对唐朝发动攻势。九月十六攻陷太原，留守太原的李元吉弃城逃走，刘武周派宋金刚继续向南进攻。唐高祖派宰相裴寂率军抵御，十月，裴寂大败，今山西全境几乎都落入了刘武周手中。唐高祖大惊，考虑放弃河东（山西省）。李世民请命亲率大军讨伐刘武周。高祖同意，派他率领军队渡过黄河。李世民与宋金刚对峙，还是没有马上交战，选择相持将宋军拖垮，同时派殷开山、秦叔宝率军击败援助叛唐势力的刘武周部将尉迟敬德、寻相。最终，武德三年（620年）四月，宋金刚粮草枯竭后退，李世民追击，宋金刚大败。尉迟敬德、寻相降唐，李世民持续追击，刘武周、宋金刚逃往东突厥。山西全境都落入唐朝手中。

平定中原

武德三年（620年）夏，唐高祖再派李世民东征郑国。619年，隋朝末代皇帝杨侗禅位给郑王王世充，王世充称皇帝，建立了郑国。李世民兵至郑都洛阳，王世充求和，李世民回绝，开始围攻洛阳。同时，他派部下分别占领了郑国周边的城池。同年冬，除洛阳和王世充的侄子王弘烈守卫的襄阳之外，郑国大部分地区都归属唐朝。王世充向河北的夏王窦建德求助。窦建德认为唐灭郑国之后，就要兼并他的夏国，于是同意出兵。他派李大师劝李世民撤退，李世民扣留李大师，没有回应窦建德。李世民在兵将中选派玄甲军一千馀人，身著黑衣黑甲，自己率领秦叔宝、尉迟敬德、程知节、翟长孙作为指挥。

武德四年（621年）春，洛阳陷入绝境，夏军尚未抵达，但唐军也进入困局，洛阳城防依靠飞石弓弩使唐军伤亡很大。唐高祖听说窦建德已决定前来援助王世充，命李世民撤退。李世民派封德彝去长安禀明高祖，如果唐军撤退，王世充势力再振，以后很难取得现在的成功了。高祖于是同意李世民继续围攻洛阳。夏国前军抵达，李世民派军将其击溃，然后致书窦建德，请他撤军。窦建德的妻子曹皇后和大臣凌敬建议，应进攻山西南部的唐军，窦建德没有同意，继续向洛阳进军。李世民预料到窦建德的行动，留下李元吉指挥围攻洛阳，自己则东进虎牢关结阵。两军在虎牢交战，李世民打败窦建德，将其俘虏。他将窦建德带到洛阳，王世充见到大惊，想要放弃洛阳南逃襄阳，但他的部将表示现在唯一能依靠的就是窦建德，窦建德被擒，已经没有胜算。王世充于是投降。逃回夏都洺州的曹皇后和齐善行随后也投降唐朝。郑国、夏国之地都归属唐朝。

自此李世民威望日隆，尤其是在虎牢之战后班师返京时，受到长安军民的隆重欢迎。高祖为赏赐李世民和李元吉铸币监各三炉，裴寂一炉，让他们自己铸币。武德四年十月，封为天策上将，领司徒、陕东道大行台尚书令，食邑增至二万户。李渊又下诏特许天策府自置官属，李世民因此辟弘文馆，收揽四方彦士入馆备询顾问，与秦王府相结合，俨然一个小内阁。

平定河北

窦建德被李世民被带回长安后，被唐高祖处决。武德四年（621年）冬，夏将刘黑闼反抗唐朝，声称要为窦建德报仇。兖州徐圆朗名义上在王世充手下为鲁王，在王世充失败后归顺唐朝。这时，刘黑闼与徐圆朗结盟，一起反唐。刘黑闼接连击败高祖的堂弟淮安王李神通、义安王李孝常和曹国公李世绩。至此，他几乎收复了原夏国疆域，定都洺州，自封为汉东王。武德五年（622年），高祖再派李世民和李元吉率军讨伐，经过一番战斗，三月廿六，李世民在洺水上筑坝，然后将其摧毁，由此引发的洪水摧毁了汉东军。刘黑闼逃到东突厥，而李世民则向东击败徐圆朗。高祖召李世民回朝，于是李元吉、李世绩、李神通、任瓌继续进攻徐圆朗，四月初九，李世民返回长安。

玄武门之变与即位

618年，李渊建立唐朝为唐高祖，并立世子李建成为太子。太原起兵是李世民的谋略，高祖曾答应他事成之后立他为太子，但天下平定后，李世民功名日盛，而高祖犹豫不决。太子李建成随即联合四弟齐王李元吉，共同排挤李世民。同时，高祖的优柔寡断，也使朝中政令相互冲突，加速了诸子的兵戎相见。太子、秦王和齐王的教书与皇帝的诏书具有同等效力，在命令相互冲突时，官员们只得执行最先到达的命令。

此后，长兄皇太子李建成知李世民终不肯屈为人臣，而李世民也认为是自己奠下唐朝开国的基业，遂与李建成、四弟齐王李元吉猜忌日深，两派之间互相倾轧。李世民的手下人才济济，李建成的支持者只有李元吉和李渊的嫔妃尹德妃、张婕妤等人。

武德五年（622年）年底，刘黑闼得到东突厥颉利可汗的支持返回河北，在下博之战大胜唐军，李世民的堂弟淮阳王李道玄阵亡。刘黑闼再次恢复了原夏国的大部分领土。李建成的谋士王圭和魏徵建议太子要在战争中提升自己的声望，李建成向父亲请战。高祖于是派李建成、李元吉率军攻打刘黑闼。武德六年（623年），刘黑闼兵败，被诸葛德威出卖，擒获交给李建成。李建成在汉东故都洺州处决了刘黑闼，凯旋回到长安。此时，唐朝基本统一中国。

接下来的几年中，李世民兄弟之争愈演愈烈。在此期间，东突厥入侵时，李建成、李世民都曾经率军防御。辅公祏在丹阳（今江苏省南京市）反唐时，唐高祖任命李世民为江州道行军元帅，攻打辅公祏，但很快取消了命令，而派李世民的堂兄赵郡王李孝恭代为出征。

武德七年（624年）六月，李建成暗中招募骁勇充当东宫卫士，郎将尔朱焕、校尉桥公山到仁智宫向避暑的唐高祖告发。唐高祖大怒，将李建成逮捕。李建成的亲信庆州都督杨文干恐惧，起兵谋反。高祖派李世民攻打杨文干，许诺平定杨文干后立他为太子。然而，李世民走后，李元吉和宰相封德彝、尹德妃、张婕妤等人都替李建成求情。李世民平定杨文干归来后，高祖并没有废黜李建成，而是指责李世民与李建成不和，将李建成的手下太子中允王圭、左卫率韦挺和李世民手下的天策兵曹参军杜淹，全都流放到巂州（今四川凉山彝族自治州）。

唐高祖困于东突厥多次入侵，想要烧毁长安，迁都樊城。李建成、李元吉、裴寂都表示同意。而李世民坚持反对，所以计划未能实施。同时，李世民也派亲信张亮、王保等人前往洛阳，加强控制当地军队和结纳山东豪杰。

李世民曾在李建成东宫饮酒，吐血数升，怀疑李建成下毒。唐高祖于是考虑派李世民出镇洛阳，以防止兄弟之间的进一步冲突。但李建成、李元吉认为这会给李世民一个在洛阳培养势力的机会，于是表示反对。高祖因此作罢。与此同时，李世民曾一度造访李元吉府邸，李元吉想要刺杀李世民，李建成却下不了决心，因而终止了行动。李建成有一匹烈马，很容易摔倒骑手，他让李世民试骑，导致李世民几次摔倒，李世民向宇文士及表示对这种伎俩的不屑。

其中宰相裴寂、谋士王圭、魏徵、东宫卫士将领薛万彻等追随李建成、李元吉。秦府谋士杜如晦、房玄龄，将领秦叔宝、尉迟敬德、段志玄、侯君集、王君廓等跟从李世民。宰相陈叔达、渭北行军典签长孙无忌等暗中支援李世民。其馀将领李靖、李世绩，大臣宇文士及等保持中立。李世民手下房玄龄、杜如晦、长孙无忌一再劝说李世民先对李建成、李元吉下手，而魏徵则劝说李建成先攻打李世民。李建成劝唐高祖翦除房玄龄、杜如晦，以及李世民的亲信尉迟敬德和程知节。留在李世民身边的长孙无忌继续劝说李世民先下手为强。

武德九年（626年）夏，东突厥侵犯唐边境。高祖本来想要派李世民率军抗击，李建成向高祖建议由李元吉做统帅，率领李世民手下的大将尉迟敬德、程知节、段志玄、秦叔宝等人出征突厥。太子府率更丞王晊密报秦王：李建成想藉此控制秦王的兵马，并准备在昆明池为李元吉饯行时，设伏兵杀李世民。于是李世民决定先发制人，让尉迟敬德暗中召见房玄龄、杜如晦回府，夜间向高祖状告李建成、李元吉淫乱后宫。高祖于是计划第二天一早召见李建成、李元吉，召宰相裴寂、萧瑀、陈叔达调查此案。次日，即武德九年六月初四庚申日（626年7月2日），李建成和李元吉通过首都长安城宫城的北门玄武门附近时，李世民带领手下进行伏击。他亲自射出一箭，射杀了皇太子李建成，尉迟敬德杀死了齐王李元吉，史称「玄武门之变」。

此后李世民的军队进宫，高祖得知情况后，知道大势已去，让出军政大权予秦王，而建成、元吉则被宣布为作乱者，诸子则遭诛杀并从宗籍中除名。三天后（六月初七癸亥日，7月5日），李世民被立为皇太子，诏曰：「自今军国庶事，无大小悉委太子处决，然后闻奏」。八月初九甲子日（9月4日），高祖退位称太上皇，禅位于李世民。李世民登基，是为唐太宗。当年十月，追封李建成为息隐王，李元吉为海陵剌王。次年改元贞观。642年，追复李建成为隐太子，李元吉为巢剌王，并将皇子李福过继李建成为嗣（后来另一皇子李明也在唐高宗年间被出继李元吉为嗣）。

贞观之治

太宗在位期间，积极推行了府兵制、租庸调制和均田制，并加强科举制等政策。贞观二年（628年），当时的人口已因隋末战争而锐减，此时唐朝只有290万户，经太宗君臣23年的努力，社会安定、经济恢复并稳定发展，至唐高宗永徽三年（652年），人口达到380万户，奠下了高宗、武则天、玄宗年间大唐盛世的基础，史称贞观之治。

太宗本身也是个既英武又善辩之人，但是有鉴于帝位得之不易，加上隋炀帝本人亦以雄健尔雅善辩闻名，隋却因此铸下灭亡的大错，因此在位期间，太宗鼓励群臣批评他的决策和风格。其中魏徵廷谏了200多次，在廷上直陈唐太宗的过失，在早朝时多次发生了使太宗尴尬、下不了台的状况。晚年的太宗因国富民强，纳谏的器度不如初期，偶尔也发生误杀大臣的遗憾，但是大致上仍克制、保有纳言的风范。

在民族政策方面，《资治通鉴》记载唐太宗在贞观二十一年（647年）平定薛延陀时，曾对他的左右大臣说：「自古帝王皆贵中华，贱夷狄，朕独爱之如一，故其种落皆视朕如父母。」，《贞观政要》也记载了唐太宗在贞观十三年（639年）封阿史那思摩为突厥可汗时说道：「中国百姓，实天下之根本，四夷之人，乃同枝叶，扰其根本以厚枝叶，而求久安，未之有也。初不纳魏徵言，遂觉劳费日甚，几失久安之道。」

太宗即帝位不久，按秦王府文学馆模式，新设弘文馆，进一步储备天下文才。另外，太宗精擅书法，以行书写碑，称「飞白」，闻名后世。著名作品有《温泉铭》、《晋祠铭》等。晚年太宗著《帝范》一书以教戒太子李治，总结了他的施政经验，同时自评一生功过。史家曾疑太宗生前，指定以东晋书法大家王羲之所作《兰亭集序》为陪葬品。近年据考古学家和历史学者研究，《兰亭集序》应该不在太宗之昭陵，而在高宗、武则天所合葬的乾陵之中。

唐太宗与身边大臣魏徵、王圭、房玄龄、杜如晦、虞世南、褚遂良等的对答也在开元十八（730年）、十九年间被吴兢辑为《贞观政要》一书，以发扬太宗励精图治的治国精神。

贞观初政

太宗即位十天，就将大批宫女简放出宫，送她们回家，这样她们在民间成家。太宗册封其妻长孙氏为皇后，长子李承乾为皇太子。

太宗定勋臣爵邑，第一等为长孙无忌、房玄龄、杜如晦、尉迟敬德、侯君集。皇帝的堂叔淮安王李神通不满自己位次在房杜之下时，太宗说房杜运筹帷幄，功劳大于在河北全军覆没的李神通。这让其他反对之声平息，因为他们见到太宗至公行赏，不私其亲，将李神通这样的宗室排在低位。太宗还以王爵之礼安葬了李建成和李元吉，并让他们的原来的属官参加了葬礼。

太宗从被立为太子之后就开始调整朝廷人事，任命自己信任的房玄龄等人成为宰相。而萧瑀、陈叔达因为在皇帝面前争忿，而双双被罢免。萧瑀很快就重新入相，他在太宗朝屡遭罢黜和复职。太宗非常重视官员对朝政的批评，使他认为朝廷的弊政得以改变。太宗特别信任魏徵，接受了魏徵的很多建议。黄门侍郎王圭有密奏，交给侍中高士廉上达，高士廉没有奏报太宗。太宗于是将高士廉出为安州大都督。太宗以隋炀帝为鉴，赏赐愿意进谏的官员，尤其是魏徵和王圭。太宗对思想持开放态度，其中在文化上，试图努力调和道教与佛教的矛盾，这体现在他晚年所作的《大唐三藏圣教序》中。

燕郡王李艺本是隋末幽州军阀，后归顺唐朝，他在武德年间与李建成亲近，且得罪过李世民。太宗即位后，李艺不自安。贞观元年（627年）正月，他在豳州叛乱。但很快被平定，李艺逃亡中被杀。四月，高祖的堂弟、凉州（今甘肃省武威市）都督长乐王李幼良的手下无赖子弟侵暴百姓，并且私下与羌胡贸易。太宗派宇文士及前去调查，李幼良的部下惊恐万分，密谋挟持他逃亡突厥。太宗得知此事后，赐李幼良自尽。九月，幽州（今北京市）都督王君廓入朝时，怀疑长史李玄道告发他的不法之事，于是杀驿吏逃亡突厥，途中被乡民所杀。十月，岭南酋长冯盎、谈殿等互相攻击，有人报告冯盎谋反，太宗在魏徵的建议下，派使者安抚冯盎，冯盎遣子入朝。

当年二月，太宗见天下州县过多，将许多州县加以合并。并在州县以上设置「道」，将唐朝分为十道：关内道、河南道、河东道、河北道、山南道、陇右道、淮南道、江南道、剑南道、岭南道。

灭东突厥

武德九年（626年）八月，因唐朝发生玄武门之变，政局不稳，东突厥伺机入侵，攻至距首都长安仅40里的泾阳（今陕西咸阳泾阳县），京师震动。此时，长安兵力不过数万，刚刚即位的太宗被迫设疑兵之计，亲率高士廉、房玄龄等6骑在渭水隔河与颉利可汗对话，怒斥颉利、突利二可汗背约。太宗赠予颉利可汗金帛财物，以求突厥退军，并与之结「渭水之盟」，突厥兵于是退去。《唐语林》记载唐太宗「空府库」以求突厥退军，在突厥归途时派李靖伏击，夺回了财物，以及数万匹马。之后，太宗励精图治，并且挑拨颉利、突利二可汗和突厥与铁勒诸部的关系。627年，东突厥内部出现分裂。反对颉利可汗的薛延陀、回纥、拔也古、同罗诸部落对其变革国俗和推行的政令不满，另立薛延陀为可汗。突利可汗也暗中与唐联络，并与颉利可汗决裂。臣服于东突厥的契丹首领大贺摩会也归顺唐朝，太宗册封薛延陀可汗夷男为真珠可汗。同时东突厥又遇到大雪气候，牲畜大多被冻死饿死，突厥势力渐弱。

突厥这时没有力量庇护最后一个隋末割据者——夏州割据势力首领梁师都，柴绍和薛万均率军围攻梁都朔方（今陕西省榆林市），贞观二年四月二十六壬寅日（628年6月3日），朔方人梁洛仁杀梁师都，归降唐朝，唐朝统一全国。

太宗决心挑战东突厥在东亚的霸主地位，于629年八月任命李靖、李世绩、柴绍、李道宗等为行军总管，令其出师塞北。各路大军由李靖总制，苏定方为先锋，出兵征讨东突厥。唐军在李靖的调遣下，贞观四年（630年）三月颉利兵败被俘，而后被押送到长安，东突厥灭亡。

天可汗

东突厥灭亡后，温彦博主张将突厥人留在唐朝边防体系之内作为防御缓冲，魏徵则主张将突厥人驱逐塞外。太宗接受了温彦博的建议，于是唐朝在东突厥突利可汗故地设置顺、佑、化、长四州都督府，颉利可汗故地置定襄都督府、云中都督府，仍由部落酋长作为都督、刺史，而没有任命新的封疆大吏来统治。漠北和西域诸国君主在长安尊称太宗为「天可汗」，意为天下总皇帝或天下共主。「天可汗」除了是一种对唐朝皇帝的荣衔，还是一种有实质意义的国际组织体系，以维持当时丝绸之路途径各同盟国的集体安全与贸易秩序。

贞观五年（631年），太宗命大臣讨论郡县制和封建制的利弊，魏徵、李百药等人反对封建制，颜师古建议让宗室子弟和功臣担任刺史，勿令过大，间以州县，杂错而居，各取郡县制和封建制的优势。太宗同意了颜师古之议。东突厥灭亡后，大臣多次请求太宗在泰山封禅，太宗开始表示拒绝，后来他的信念动摇时，又被魏徵一再劝阻，魏徵指出封禅会导致百姓供顿劳费、开支巨大，而且让远夷君长看到中原因战乱导致的荒芜，对国防也不益。太宗于是采纳了他的建议。

贞观八年（634年），太宗派李靖、萧瑀等十三位高官为诸道黜陟大使，巡视地方官能否查明民苦，安抚贫民，选拔贤能。李靖最初推荐魏徵，太宗不同意，说魏徵要留在自己身边指出他的错误，他一天都不能让魏徵离开。

平定吐谷浑

吐谷浑可汗伏允听信大臣天柱王的建议，屡次侵犯唐朝的西部边境。伏允曾想让他的儿子尊王迎娶唐朝公主，太宗坚持让尊王来长安举行婚礼，于是和亲未成。634年，扣留唐朝使者赵德楷，六月，太宗以段志玄、樊兴为行军总管，讨伐伏允。吐谷浑军队机动性强，避免正面交锋，段志玄虽未战败，但也未能大获全胜。十二月，又以李靖、侯君集、李道宗、李大亮、李道彦、高甑生等为行军总管，率领薛万均、薛万彻、契苾何力等将领，大举讨吐谷浑。635年，李靖大军队击溃吐谷浑，伏允败走，被部下所杀。伏允之子慕容顺杀死天柱王，自立为可汗，投降唐朝，太宗册封慕容顺为吐谷浑可汗。慕容顺死后，636年，太宗册封慕容顺之子诺曷钵为吐谷浑可汗。

氏族志

635年五月，太上皇高祖李渊驾崩，太宗在服丧期间，曾短暂让太子李承乾监国，六月，太宗重新听政，此后仍授权李承乾处理细务。636年春，太宗任命皇弟、皇子为刺史，按授命之地更改王号。636年秋，长孙皇后去世，太宗悲痛哀悼，亲笔为她题碑文。

637年夏，太宗重新考虑分封制，制定了刺史袭封制度。将皇弟、皇子和功臣除保留现有职位外，还获得了州刺史的职位，并可以传给他们的后代。于是设立了35个世袭刺史及都督。不久后，这个计划遭到了以长孙无忌为首的功臣们的反对，639年，太宗于是取消了这一制度。

太宗不满崔、卢、李、郑等山东士族，认为他们自衿高门。638年，命高士廉、韦挺、令狐德棻、岑文本编撰《氏族志》，意图将士族根据名望、功勋、善恶分为九类。然而，在高士廉提交的初稿中，仍然将崔民干的博陵崔氏列为第一等。太宗不满，因为他指出高士廉只看传统名望，不看近世功勋。因此，太宗亲自干预修改，以皇族李姓为首，外戚长孙氏为次，将崔氏家族降为三等。

和亲吐蕃

在青藏高原上，吐蕃日渐兴起，至六世纪末与吐谷浑、苏毗为高原上三大势力。七世纪初，赞普松赞干布即位，统一了高原，又征服了位于西藏西部的苏毗、阿里地区的羊同和尼婆罗（今尼泊尔）。

634年，吐蕃赞普松赞干布遣使与唐朝修好，唐朝也派使臣冯德遐入蕃。636年，松赞干布派专使去长安请婚，唐朝不允。638年，松赞干布遂藉口唐朝属国吐谷浑从中作梗，亲自指挥大约20万吐蕃军，出兵入侵吐谷浑，并开始攻击唐朝的松州（今四川阿坝藏族羌族自治州）。但同时松赞干布又派遣使者到唐朝国都长安再次请求，并宣称他们打算欢迎公主。唐太宗派侯君集为当弥道行军大总管指挥5万军队，执失思力、牛进达、刘简协助，援救松州。与此同时，吐蕃军正在围困松州的首县－嘉诚（今四川松潘），但唐军先遣部队在牛进达指挥下，打败了吐蕃军。唐军在松州大胜吐蕃军，但唐朝也见识到了吐蕃的力量。640年，松赞干布又派大臣禄东赞使唐求婚，唐太宗便以宗室之女文成公主许嫁于吐蕃赞普松赞干布，并派礼部尚书江夏王李道宗持节护送。641年，唐室文成公主下嫁于吐蕃的松赞干布，吐蕃赞普于是接受唐朝的册封。《新唐书》记载文成公主入蕃时，松赞干布亲迎于柏海。吐蕃派豪族子弟到长安学习《诗》、《书》。唐高宗继位后，又通过赏赐松赞干布和文成公主把各种汉地的生产技术转入吐蕃。

观史书己

贞观九年十月，即李渊死后五个月，李世民第一次要求观览《起居注》，未遂。

《贞观政要·卷七·论文史第二十八》记载：贞观十三年，褚遂良为谏议大夫，兼知太宗《起居注》。唐太宗欲查看起居注，褚遂良以「不闻帝王躬自观史」为由拒绝了。唐太宗说：「朕有不善，卿必记耶？」褚遂良说：「臣职当载笔，何不书之？」黄门侍郎刘洎进言：「人君有过失，如日月之蚀，人皆见之。设令遂良不记，天下之人皆记之矣。」《旧唐书·褚遂良传》和《资治通鉴·唐纪十二》也载有此事。

次年（640年），唐太宗再度要求看《起居注》，宰相房玄龄等人就删减整理国史，撰写成《高祖实录》和《太宗实录》各二十卷。当太宗见到「六月四日事，语多微文」——指史官对当年玄武门事变内容含糊其辞，多有隐讳文饰之语，便以当年房玄龄劝他政变时「遵周公之事，外宁区夏，内安宗社」的说法，向房玄龄表示：不必替他遮遮掩掩，反正玄武门事件本来就是像「周公诛管、蔡，季友鸩叔牙」之义举，目的是为了「安社稷、利万民」，要求「削去浮词，直书其事」。《资治通鉴·唐纪十三》亦有记载。

这一行为遭到章太炎指责：「太宗即立，惧于身后名，始以宰相监修国史，故两朝《实录》无信辞。」吕思勉、黄永年等学者也附和章太炎的观点，认为唐太宗对史书记载有所修饰。

诸子夺嫡

皇子亲王出任地方刺史，唯有魏王李泰、晋王李治留在长安。李泰受到太宗的重视。太宗因为李泰喜欢文学，允许李泰聘请文人作为僚属，编纂《括地志》。长孙皇后去世后，因为李泰受宠，出现了太宗可能让他取代太子李承乾的议论，李承乾的支持度开始减弱。

到642年，李泰已经有了取代太子的野心，一些官员开始分化为太子派和魏王派。太宗在魏徵、褚遂良的劝说下，采取行动表明稳固太子的地位。但他继续偏爱李泰的做法，不断引起大臣们的猜测。643年春，魏徵去世，太宗悲痛哀悼，亲自为魏徵立碑，并在魏徵去世前，许诺将女儿衡山公主嫁给魏徵的儿子魏叔玉。太宗派人在凌烟阁绘制二十四功臣图。

643年春，太宗五子齐王李佑因长史权万纪常加于他诸多限制，而愤愤不平，于是他杀了权万纪，在齐州起兵叛乱。太宗派李世绩讨伐打李佑，大军未至，李佑就被自己的部下杜行敏俘送到长安，太宗命他在内侍省自杀，同党四十四人被诛，其馀不问。

太子李承乾经常说突厥语，穿著突厥服装，甚至在自己的住所里搭起帐篷，模仿突厥可汗。李承乾怕太宗废黜自己而立李泰，与侯君集、太宗之弟汉王李元昌、将军李安俨、他的姑表兄赵节、杜如晦之子杜荷等人合谋夺位。在追查李佑之乱时，李承乾的侍卫纥干承基被牵连，为了自救，他揭发李承乾的阴谋。太宗闻讯大惊，命长孙无忌、房玄龄、萧瑀、李世绩，会同大理、中书、门下等官署进行联合调查。太宗在通事舍人来济的建议下，太宗废黜李承乾的太子之位，而没有杀他，命李元昌自杀，侯君集、李安俨、赵节、杜荷被处决。

李承乾被废黜后，太宗向李泰许诺，立他为太子。但随著深入调查，太宗认为李承乾的谋反是受到李泰的逼迫，因此决定废黜李泰。

《资治通鉴》记载，太宗贞观十七年废太子李承乾之后、改立李治为皇太子之前，李世民之三子一弟（长子李承乾、四子李泰、五子李佑、及七弟李元昌）俱谋取帝位，致太宗心灰意冷之曲折，史载：「承乾既废，上御两仪殿，群臣俱出，独留长孙无忌、房玄龄、李世绩、褚遂良，谓曰：『我三子一弟，所为如是，我心诚无聊赖！』因自投于床，无忌等登前扶抱，上又抽佩刀欲自刎，遂良夺刀以授晋王治。」

太宗决定立晋王李治为太子，李承乾流放了黔州，李泰出居均州。太宗为太子李治选良家女充实东宫，被李治推辞。太宗怀疑李治的仁弱性格，是否足以继承天下，他谘询长孙无忌是否可以立自己和隋炀帝之女杨妃之子吴王李恪为太子，被长孙无忌坚决反对而未成。

由于魏徵生前曾推荐侯君集和杜正伦有宰相之才，太宗开始怀疑魏徵也参与了阴谋。于是扑倒了自己撰写的魏徵之碑，取消了魏叔玉与衡山公主的婚约。

征讨高句丽

642年冬，高句丽发生政变，最终导致了唐朝和高句丽的战争。642年天，高句丽荣留王不满东部大人渊盖苏文专横，与他的大臣密谋杀死渊盖苏文。渊盖苏文得到消息，发动政变，杀死了荣留王和同谋官员。拥立荣留王的侄子高藏为王，并自封为「大莫离支」摄政。有人建议攻打高句丽，最初太宗表示拒绝。

644年，高句丽攻打新罗，新罗请求唐朝援助。为征讨渊盖苏文和保护唐朝的盟友新罗，唐太宗认为有必要对高句丽开战。他逮捕了盖苏文派到唐朝的使者，宣布其弑逆之罪。644年，太宗率领李世绩、李道宗、张亮和长孙无忌统军10万亲征高句丽。645年，太宗率领唐军攻占了辽东（今辽宁省辽阳市），冲破高句丽的防线准备攻打高句丽国都平壤，似乎大功在即。太宗亲自率领唐军三万，击败高句丽将军高延寿、高惠真率领的十五万大军，围攻安市城（今辽宁省鞍山海城市）。不料在安市受阻，再也无法前行。深秋时节，唐军粮草枯竭，冬天将至，太宗于是撤军。他后悔贸然亲征，说：「魏徵若在，不使我有是行也。」他重新为魏徵立碑，召见魏徵妻儿，深加劳赐。

在这之后，太宗对高句丽的进攻仅维持在一些小规模的突袭。646年，唐朝与回纥击灭薛延陀后，647年，唐太宗令牛进达率兵从海上、李世绩率兵从陆路攻打辽东半岛。648年，太宗再派薛万彻率军从海上攻打鸭绿江口。随后，唐开始集结陆海部队准备在649年再一次大规模攻高句丽。不过太宗于649年去世后，新皇帝唐高宗暂停东征的计划。668年，高宗联合新罗灭亡高句丽，载籍户数69.7万。并建立安东都护府等加以控制辽东。

灭薛延陀

东突厥灭亡后，薛延陀的真珠可汗乙失夷男接管了东突厥的故土。薛延陀表面臣服于唐朝，暗中却扩充自己的力量。638年，对于薛延陀逐渐强大，太宗怕之后难以控制，于是给真珠可汗的两个儿子拔灼、颉利苾授予小可汗的头衔，试图在他们内部制造矛盾。

639年夏，突利可汗之弟结社率与突利可汗之子贺逻鹘勾结，计划刺杀太宗。他们本打算等著晋王李治一早离开行宫时，趁机袭击。而到了计划的当天，晋王没有离开宫殿，结社率于是提早行动，但很快失败，被俘虏处决。这次事件之后，大臣们建议将突厥人从河套地区的黄河以南遣返到黄河以北。太宗也试图恢复东突厥，以抗衡薛延陀的崛起。639年秋，太宗册封突厥王族怀化郡王李思摩（阿史那思摩）为乙弥泥孰俟利苾可汗，作为重建的东突厥国家的首领，将诸州安置的所有突厥和胡人都交给了他。突厥人害怕薛延陀，不敢出塞。太宗下诏让真珠可汗与李思摩保持和平，各守漠北和漠南，不互相攻击。在真珠可汗保证不进攻后，突厥人于是出塞在漠南建牙。

薛延陀为避免新恢复的东突厥站稳脚跟，与其进行了多次战争。641年冬，真珠可汗听说太宗即将在泰山封禅，无法支持东突厥，于是派其子大度设率军攻打东突厥。李思摩被迫退入长城。太宗为保住东突厥，命李世绩与张俭、李大亮、张士贵、李袭誉率军攻打薛延陀。李世绩很快在诺真河（流经今内蒙古包头市）击败大度设，大度设逃走。

642年，薛延陀尽管名义上顺从唐朝，但已经构成了严重的威胁。太宗这时有两种选择：武力征服或将女儿嫁给真珠可汗进行和亲。唐朝将领、契苾部落的首领契苾何力，被部下掳走，献给薛延陀。为了赎回契苾何力，太宗同意将女儿新兴公主嫁给真珠可汗，真珠可汗于是释放了契苾何力。643年，唐太宗认为自己向真珠可汗许诺和亲并不明智，所以向薛延陀要聘礼：五万匹马、一万头牛和骆驼、十万只羊。真珠可汗同意，但无法立即交纳。太宗以此为由，取消了婚约。

但是644年，趁太宗征伐高句丽的机会，薛延陀部队发起新一轮攻势，击败东突厥，东突厥部众抛弃了可汗李思摩，逃回唐朝境内。阿史那思摩只得逃回云州，太宗以他为右武卫将军。随后，高句丽寻求薛延陀援助，但夷男希望避免与唐朝直接战斗。

645年，夷男死后，他的儿子多弥可汗拔灼开始和唐军作战，攻打唐朝黄河以南和夏州。646年，唐将乔师望、执失思力率军反击并打败拔灼后，薛延陀的附庸回纥、仆骨、同罗等铁勒部落也乘机出兵造反。太宗得知后，派李道宗、阿史那社尔、执失思力、契苾何力、薛万彻、张俭率军大举进攻薛延陀。薛延陀受到多方攻击，回纥军将多弥可汗杀死。馀下的薛延陀人纷纷逃亡，拥立拔灼的堂兄咄摩支为伊特勿失可汗，咄摩支向唐朝表示取消可汗之号。李世绩军至郁督军山，咄摩支的部落还想顽抗，被唐军击败。咄摩支向唐军投降，被带到长安，结束了其对漠北的统治。薛延陀灭亡后，其他臣服于薛延陀的部族，此时也都表示臣服于唐朝，以太宗为天可汗。

太宗于铁勒故地设六府七州：瀚海府（回纥）、金微府（仆骨）、燕然府（多滥葛）、卢山府（思结）、龟林府（同罗）、幽陵府（拔野古）。七州：皋兰州（浑）、高阙州（斛薛）、鸡鹿州（奚结）、鸡田州（阿跌）、榆溪州（契苾）、蹛林州（思结别部）、填颜州（白霫）。由燕然都护府管理，治所在阴山之麓（今内蒙古杭锦后旗），辖境东到大兴安岭、西到阿尔泰山、南到戈壁、北到贝加尔湖的整个蒙古高原。回纥的首领吐迷度，虽顺服唐朝，但也试图控制漠北，648年他被侄子谋杀，直到九十多年后，回纥汗国才得以建立。

设立安西四镇

唐太宗灭东突厥后，开始对西域（即现代新疆和中亚地区）的西突厥以及一些松散结盟绿洲国家的施加军事实力，其主要针对西突厥，以恢复两汉以来对西域的统治。从640年开始，太宗进行一系列针对西突厥及其在塔里木盆地绿洲仆从国的战役。西突厥与唐朝之间的斗争，持续到太宗之子高宗在位时的657年，西突厥战败被唐朝彻底征服。

632年，疏勒国、于阗国向唐朝入贡，635年，处月国（伊犁河流域）向唐朝入贡，636年，朱俱波（今新疆叶城）向唐朝入贡。高昌王麴文泰原本臣服于唐朝，因为攻打焉耆，就和唐朝的矛盾越来越大，他与西突厥欲谷设联合，阻碍西域商路，进攻唐朝的伊州。639年冬，太宗以侯君集为交河道行军大总管，与薛万均率兵出击高昌王麴文泰。640年，唐军至碛口，麴文泰惊惧而病死。其子麴智盛即位后不久，侯君集围城，麴智盛请罪，侯君集要求他出城投降，麴智盛没有同意。侯君集击败西突厥在可汗浮图城的援军，麴智盛于是献城投降唐军。高昌国三州、五县、二十二城，八千户、三万馀人归属唐朝，高昌国结束。魏徵指出在高昌驻军，花费和人力成本都很高，建议太宗让麴智盛继续为高昌王。太宗没有同意，唐朝在高昌设置西州，将其全境并入唐朝的版图。

640年，唐朝在交河城设安西都护府，用以针对西突厥和管理西域。焉耆王龙突骑支协助唐朝征讨高昌，之后又与西突厥结盟，644年，西突厥的盟友焉耆攻打西州，安西都护郭孝恪为西州道行军总管，从安西（即高昌）出兵讨伐依附西突厥的焉耆，占领焉耆，俘虏国王龙突骑支，立其弟龙栗婆准摄国事。但后来，西突厥大臣屈利啜随后攻陷焉耆，俘获龙栗婆准，焉耆再次脱离唐朝。屈利啜惧怕唐朝势力，不久撤出，焉耆贵族立龙突骑支堂弟龙薛婆阿那支为王。

648年，唐太宗派遣阿史那社尔、郭孝恪率军讨伐依附西突厥的焉耆和龟兹（今新疆阿克苏地区库车县），唐军击斩龙薛婆阿那支，立他的堂弟龙先那准为王。阿史那社尔进军龟兹，俘虏其王白诃黎布失毕，立其弟为王，征服两国。然后疏勒和于阗归附唐朝，将安西都护府迁至龟兹，抚宁西域，统龟兹、焉耆、于阗、疏勒四国，史称安西四镇。

贞观疆域

在北方，贞观四年（630年），唐军灭亡东突厥，漠南成为唐势力范围。贞观二十年（646年），又一举消灭了薛延陀汗国，至此大漠南北广大地区皆为唐的势力范围。唐朝廷在漠北设立安北都护府，在漠南设立单于都护府，建立了南至罗伏州（今越南河静）、北括玄阙州（后改名余吾州，今安加拉河地区）、西及安息州（今乌兹别克斯坦布哈拉）、东临哥勿州（今吉林通化）的辽阔疆域。

在西北，贞观四年，唐朝廷在伊吾七城设立西伊州，开始经营西域。贞观二十二年（648年），郭孝恪击败龟兹国，把安西都护府治所迁至龟兹。

在东北，645年唐太宗征讨高句丽未果，唐高宗在668年乃联合新罗灭高句丽，设立安东都护府。

渐不克终

面对自己空前的文治武功，太宗到晚年也出现一些过失。首先纳谏不如贞观早期积极，比如贞观十年，魏徵发现他「渐恶直言」。其次奢侈之风日重。不过晚年他还是能反省自己过度奢靡的错误。司马光说唐太宗：「好尚功名，不及礼乐，父子兄弟之间，惭德多矣」。同时，太宗晚年也由早年的清静转为奢纵，营建宫殿，计划封禅泰山等，并自辩「百姓无事则骄逸，劳役则易使」，魏徵因此谏到「恐非兴邦之至言，岂安人之长算？」不过由于太宗晚年能够清醒认识自己的问题，所以也能进行调整，因此虽然太宗晚年存在这些过失，最终没有出现败亡的危机，「功大过微，故业不堕」，维持了贞观之治的局面。

与拜占庭帝国的联系

《旧唐书》和《新唐书》提到了拂菻（拜占庭帝国）几次出使唐朝。认为拂菻相当于之前的大秦（汉代时指罗马帝国）。643年波多力（君士坦斯二世）向太宗皇帝派遣使臣，献上红玻璃和绿宝石等礼物。这些史书也粗略记载了拂菻的风俗和君士坦丁堡的城墙，以及大食（阿拉伯帝国）大将军摩栧（穆阿维叶一世，在成为哈里发之前担任叙利亚总督）将其包围，迫使拜占庭人请和的战争。萨珊帝国的最后一位统治者伊嗣俟三世在哈里发政权攻打波斯核心脏地带时，派遣使者到中亚费尔干纳的宗主国唐朝寻求太宗皇帝的援助。这可能促使拜占庭人在叙利亚被穆斯林占领的情况下，派遣使节前往中国。唐朝的史料还记录了在伊斯兰哈里发征服波斯后，萨珊王朝的王子卑路斯三世逃往唐朝的情况。

在太宗统治下中国向中亚扩张，似乎已经引起了西方世界的注意。狄奥菲拉克特·西莫卡塔是希拉克略统治时期的拜占庭帝国历史学家，他写道，桃花石（Taugast、Taugas、古突厥语: Tabghach，一说语源来自建立北魏的鲜卑族拓跋氏），是一个伟大的东方帝国，统治著突厥民族, 首都在印度东北约1500英里处，称之为胡姆丹（来自突厥语Khumdan，意思是长安）。那里有偶像崇拜，但人们很聪明，遵照正义公正的法律而生活。他将中国描绘为被一条大河（即长江）分割，这条大河是两个交战敌对国家之间的边界。在拜占庭皇帝莫里斯统治期间，北方人黑衣国征服了南方的红衣国。该记述可能与隋文帝灭亡陈朝、统一中国有关。西莫卡塔将桃花石的统治者称为ταϊσαν，解释为天之子，可能是天子之意，也可以与当时统治者太宗一词的对音有关。

去世

贞观二十二年（648年）正月，唐太宗撰写《帝范》十二篇颁赐给太子李治。贞观二十三年（649年），唐太宗得了痢疾（一种传染病），医治最终无效（一说是服用天竺长生药致暴病不救），命李治到金掖门代理国事。贞观二十三年五月二十六日（649年7月10日），唐太宗李世民崩逝于终南山翠微宫含风殿内，享年五十一岁，在位二十三年，初谥文皇帝，庙号太宗，葬唐昭陵（位于今中国陕西省礼泉县东北50多里山峰上），唐高宗上元元年（674年）加谥文武圣皇帝，唐玄宗天宝八年（749年）加谥文武大圣皇帝，天宝十三年（754年）加谥文武大圣大广孝皇帝。

评价

• 《贞观政要》赞贞观之治：官吏多自清谨，王公妃主之家，大姓豪猾之伍，无敢侵欺细人。商旅野次，无复盗贼，囹圄常空，去年犯死者仅二十九人。又频致丰稔，米斗三钱，马牛布野，外户不闭，行旅自京师至于岭表，自山东至于沧海，皆不赍粮，取给于路。入山东村落，行客经过者，必厚加供待，或发时有赠遗。此皆古昔未有也。

• 后晋官修正史《旧唐书》刘昫等的评价是：「史臣曰：臣观文皇帝发迹多奇，聪明神武。拔人物则不私于党，负志业则咸尽其才。所以屈突、尉迟，由仇敌而愿倾心膂；马周、刘洎，自疏远而卒委钧衡。终平泰阶，谅由斯道。尝试论之：础润云兴，虫鸣螽跃。虽尧、舜之圣，不能用梼杌、穷奇而治平；伊、吕之贤，不能为夏桀、殷辛而昌盛。君臣之际，遭遇斯难，以至抉目剖心，虫流筋擢，良由遭值之异也。以房、魏之智，不逾于丘、轲，遂能尊主庇民者，遭时也。或曰：以太宗之贤，失爱于昆弟，失教于诸子，何也？曰：然，舜不能仁四罪，尧不能训丹朱，斯前志也。当神尧任谗之年，建成忌功之日，苟除畏逼，孰顾分崩，变故之兴，间不容发，方惧「毁巢」之祸，宁虞「尺布」之谣？承乾之愚，圣父不能移也。若文皇自定储于哲嗣，不骋志于高丽；用人如贞观之初，纳谏比魏徵之日。况周发、周成之世袭，我有遗妍；较汉文、汉武之恢弘，彼多惭德。迹其听断不惑，从善如流，千载可称，一人而已！赞曰：昌、发启国，一门三圣。文定高位，友于不令。管、蔡既诛，成、康道正。贞观之风，到今歌咏。」

• 北宋官修正史《新唐书》欧阳修、宋祁等的评价是：「甚矣，至治之君不世出也！禹有天下，传十有六王，而少康有中兴之业。汤有天下，传二十八王，而其甚盛者，号称三宗。武王有天下，传三十六王，而成、康之治与宣之功，其馀无所称焉。虽《诗》、《书》所载，时有阙略，然三代千有七百馀年，传七十馀君，其卓然著见于后世者，此六七君而已。呜呼，可谓难得也！唐有天下，传世二十，其可称者三君，玄宗、宪宗皆不克其终，盛哉，太宗之烈也！其除隋之乱，比迹汤、武；致治之美，庶几成、康。自古功德兼隆，由汉以来未之有也。至其牵于多爱，复立浮图，好大喜功，勤兵于远，此中材庸主之所常为。然《春秋》之法，常责备于贤者，是以后世君子之欲成人之美者，莫不叹息于斯焉。」

• 《新唐书·北狄列传》：唐之德大矣！际天所覆，悉臣而属之；薄海内外，无不州县，遂尊天子曰「天可汗」。三王以来，未有以过之。至荒区君长，待唐玺纛乃能国；一为不宾，随辄夷缚。故蛮琛夷宝，踵相逮于廷。

• 陆九渊《象山语要·卷三十一·论德仁功利》：「太宗富有天下，贵为天子，功业皆其所自致，而能俯首抑意，听拂逆之辞于畴昔所恶之臣。呜呼！此其所以致贞观之治，庶几于三代之王者乎？」

• 朱熹与陈亮书：「太宗之心，则吾恐其无一不出于人欲也。直以其能假仁假义，以行其私。而当时与之争者，才能知术既出其下，又不知有仁义之可饬。是以彼善于此，而得以成其功尔。」「论后世人，不当尽绳以古人礼法。毕竟高祖不当立建成。」「太宗功高，天下所系属，亦自无安顿处，只高祖不善处置了。」

• 文天祥《古代状元卷:文天祥殿试卷》：太宗全不知道、闺门之耻、将相之夸、末年辽东一行、终不能以克其血气之暴、其心也骄。

• 元朝戈直在《贞观政要》集论中说：「夫太宗之于正心修身之道，齐家明伦之方，诚有愧于二帝三王之事矣。然其屈己而纳谏，任贤而使能，恭俭而节用，宽厚而爱民，亦三代而下，绝无而仅有者也。后之人君，择其善者而从之，其不善者而改之，岂不交有所益乎！」这里所说，太宗在正心修身，齐家明伦方面，有愧于二帝三王之事，主要是指太宗与其兄李建成的皇位之争。

• 明朝官修皇帝实录《明太祖实录》记载，明太祖朱元璋在洪武七年八月初一日（1374年9月7日），亲自前往南京历代帝王庙祭祀三皇、五帝、夏禹王、商汤王、周武王、汉高祖、汉光武帝、隋文帝，唐太宗、宋太祖、元世祖一共十七位帝王，其中对唐太宗李世民的祝文是：「惟唐太宗皇帝英姿盖世，武定四方，贞观之治，式昭文德。有君天下之德而安万世之功者也。元璋以菲德荷天佑人助，君临天下，继承中国帝王正统，伏念列圣去世已远，神灵在天，万古长存，崇报之礼，多未举行，故于祭祀有阙。是用肇新庙宇于京师，列序圣像及历代开基帝王，每岁祀以春、秋仲月，永为常典。今礼奠之初，谨奉牲醴、庶品致祭，伏惟神鉴。尚享！」

• 明宪宗在命儒臣订正重刊《贞观政要》时写道：「太宗在唐为一代英明之君，其济世康民，伟有成烈，卓乎不可及已。所可惜者，正心修身，有愧于二帝三王之道，而治未纯也。」

• 毛泽东评价李世民说：「李世民的工作方法有四」，「自古能军无出李世民之右者，其次则朱元璋耳。」

• 王仲荦《隋唐五代史》：「唐代的皇帝里，唐太宗，早年的唐玄宗，唐宣宗，都是杰出的皇帝。」「我们认为旧日的封建历史家对『贞观之治』是渲染得有点过分的。……固然，在唐太宗统治的二十多年间，人口有了较大的增长，但比之隋极盛时户数，还不到二分之一。」「魏徵疏文中也说到：『今自伊洛以东，暨于海岱，灌莽巨泽，茫茫千里、人烟断绝，鸡犬不闻。道路萧条，进退艰阻。』」「封建历史家把贞观时期当作理想的太平盛世，和实际情况是有很大距离的。」

• 吕思勉《隋唐五代史》：「唐太宗不过中材，论其恭俭之德，及忧深思远之资，实尚不如宋武帝，更无论梁武帝；其武略亦不如梁武帝，更无论宋武帝，陈武帝矣！」

出生年月争议

据《贞观政要》李世民的生日是十二月癸丑，据《资治通鉴》李世民的生日是十二月癸未，据《旧唐书》李世民生于隋开皇十八年十二月戊午（599年1月23日），因此李世民的生日应为十二月份。据《旧唐书》李世民卒年五十二岁，其弟李玄霸无考；据《新唐书》李世民卒年五十三岁，其弟李玄霸年十六岁死于隋大业十年（614年），则李玄霸生卒年为公元599－614年，而李世民生卒年为公元597－649年；李世民以十二月出生，李世民生卒年月为598年1月－649年7月，与李玄霸（599－614）为同母兄弟。《新唐书》推翻了《旧唐书》关于李世民的生卒年月，增加了李玄霸的生卒年，使李世民与李玄霸的生卒更可信。胡如雷著《李世民传》即以《新唐书》为依据，考证李世民的出生年月为隋开皇十七年十二月戊午（598年1月28日）。

《新唐书》增加了李玄霸的生卒年岁，补正了李世民的生卒年岁，补充了《旧唐书》中没有的珍贵史料，《新唐书》与《旧唐书》同被列为《二十四史》之钦定官史。据胡如雷考证：「李世民生于开皇十八年十二月之说亦难成立，因窦氏在不到十三个月的时间里先后两次生子的可能性虽然不能完全排除，但就常情而言，这种可能性也不大」。根据李世民同母弟李玄霸十六岁时死于大业十年，而倒推出李玄霸生于开皇十九年，所以若李世民生于开皇十八年十二月，则李玄霸最迟生于开皇十九年十二月，两兄弟生辰过近，不太可能。

轶事

改名

《旧唐书·本纪第二：太宗上》记载，李世民四岁时，其父李渊任岐州刺史，有一书生自称善相，拜访李渊说：「公贵人也，且有贵子。」见到李世民时又说：「龙凤之姿，天日之表，年将二十，必能济世安民矣。」李渊害怕这话走漏，派人去追杀书生，书生却忽然失踪了。于是李渊就取「济世安民」之意给李世民命名。

救驾

据新旧唐书太宗本纪，李世民十六岁时参军，跟随隋将云定兴，一次隋炀帝杨广被围，云定兴军负责救驾，李世民献计，故布疑阵，吓退敌军，救回天子。

尚书令

由于唐太宗在即位前曾当过尚书令，故当太宗做皇帝后，大臣多不敢任其职，于是之后这个职务就几乎不授人，尚书省的长官就只设左、右仆射，后用其他官员以「同中书门下三品」的头衔参预朝政，执行宰相职务。至高宗时，又用低级官员以「同中书门下平章事」的头衔参预朝政，执行宰相职务。左、右仆射成了听令执行的官员，不能参加大政，唐中宗神龙政变复辟之后，仆射就非宰相职务。中书令、侍中在安史之乱后也不常设了。同中书门下平章事成了宰相最普遍的名称。

武功

《大唐新语·卷一》载，太宗继位后曾在苑囿内狩猎，一群野猪从森林中冲出。太宗举弓四箭射杀了四只，但还是有一头雄野猪向马匹直冲而来。吏部尚书唐俭慌忙下马，与之搏斗。太宗拔剑砍死野猪，笑著对唐俭说，「天策长史，不见上将击贼耶？何惧之甚！」唐俭当即回答道：「汉祖以马上得之，不以马上理之。陛下以神武定四方，岂复逞雄心于一兽！」太宗觉得唐俭说得有理，于是停止了狩猎。

避讳

李治登基后，为了表示对他的父亲李世民的无比尊敬，进行了一项重要规定，即不再使用「世」和「民」这两个字。 这个规定导致了「观世音菩萨」这个名字的改变，从此称为「观音菩萨」。在唐太宗李世民的统治时期，"观世音菩萨"这个称呼经常在大唐相关文献和文化中出现。 然而，唐太宗过世后，这个称呼变得相对不常见，逐渐淡出了历史舞台。 这个变化反映了不同历史时期和统治者对于宗教和文化方面的关注和偏好的变化。但也有说法认为「观音菩萨」只是「观世音菩萨」的简称。唐代清凉澄观法师指出在梵文古本中存在两种不同的名称，1927年新疆出土的古抄本中，以 अवलोकितस्वर（Avalokitasvara）为观音菩萨的名称，证实了他的说法。「娑伐罗」（स्वर svara），意思为「声音」，Avalokitasvara 可意译为「观音」，鸠摩罗什出生在西域地区，所见的应该就是这个版本。因此，观音菩萨并非是因为避讳而出现的名称。根据唐代玄应的说法，这可能是来自于不同地区方言所导致的。

书法

李世民酷爱书法，其书法以隶书见长，并且酷爱书法名品《兰亭序》（即《兰亭集序》，王羲之书法珍品，王羲之的字十分多变，就一「之」字就有十数种变化之多），相传当年大臣萧翼见太宗似有郁结难纾，问之原因，知道其欲得《兰亭序》，于是便与辩才和尚（王羲之当年墨宝辗转传至其七世孙智永，智永出家为僧，又将墨宝传予其弟子辩才和尚）斗智最后终于为李世民获得。而王羲之本愿并不想《兰亭序》落入君王之手成为陪葬品。但最后结果事与愿违，《兰亭序》最终成为唐太宗的陪葬品。

太宗怀鹞

唐代刘餗《隋唐嘉话》载，太宗曾经饲养过一只鹞，十分喜爱它，经常把它架在手臂上玩赏。一次看到魏徵前来奏事，就把鹞藏在了怀里。魏徵看出端倪，汇报事情时就顺势向太宗讲述古代帝王由于安逸享乐而亡国的故事，暗中劝谏太宗。魏徵奏事时故意拖了很久，鹞最终被捂死在了太宗怀里。

文皇思女

功臣长孙顺德因女儿逝世而大病。太宗认为顺德系出鲜卑贵胄，身为武将却十分挂念儿女之情，因此心生鄙夷，对房玄龄说：「顺德无刚气，因儿女牵爱而致大病，至于吗？」。后来晋阳公主早夭，年十二，太宗非常伤心，有三十多天吃不下饭，每日哀伤数十次，因此身体急速消瘦。大臣们前来劝他，太宗回道：「朕哪里不知道这样悲爱无济于事呢。我只是忍不住啊，朕也不知道为甚么会这样。」北宋时庄绰也说唐太宗儿女牵爱，不能自拔。

晋阳公主去世后，唐太宗下诏命令有关官员用晋阳公主封邑的余钱在公主墓旁营建佛祠，以此为公主的往生祈祷。

大臣

十八学士

• 秦王府属杜如晦

• 秦王府记室房玄龄

• 天策府从事中郎于志宁

• 天策府军咨祭酒苏世长

• 天策府记室薛收

• 秦王府文学褚亮

• 国子助教陆德明

• 秦王府文学姚思廉

• 国子助教孔颖达

• 秦王府主簿李玄道

• 天策府仓曹李守素

• 秦王府记室虞世南

• 秦王府参军蔡允恭

• 秦王府参军颜相时

• 宋州总管府户曹许敬宗

• 秦王府参军薛元敬

• 国子助教盖文达

• 秦王府咨议典签苏勖

凌烟阁二十四功臣

• 司徒、赵国公长孙无忌

• 故司空、扬州都督、河间元王李孝恭

• 故司空、莱国成公杜如晦

• 故司空、相州都督、太子太师、郑国文贞公魏徵

• 司空、梁国公房玄龄

• 开府仪同三司、尚书右仆射、申国公高士廉

• 开府仪同三司、鄂国公尉迟敬德

• 特进、卫国公李靖

• 特进、宋国公萧瑀

• 故辅国大将军、扬州都督、褒忠壮公段志玄

• 辅国大将军、夔国公刘弘基

• 故尚书左仆射、蒋忠公屈突通

• 故陕东道行台右仆射、郧节公殷开山

• 故荆州都督、谯襄公柴绍

• 故荆州都督、邳襄公长孙顺德

• 洛州都督、郧国公张亮

• 光禄大夫、吏部尚书、陈国公侯君集

• 故左骁卫大将军、郯襄公张公谨

• 左领军大将军、卢国公程知节

• 故礼部尚书、永兴文懿公虞世南

• 故户部尚书、渝襄公刘政会

• 光禄大夫、户部尚书、莒国公唐俭

• 光禄大夫、兵部尚书、英国公李世绩

• 故徐州都督、胡壮公秦叔宝

宰相

• 萧瑀（626年任尚书左仆射，627年任尚书左仆射，630年以御史大夫参议朝政，635年-636年以特进参豫朝政，643年-646年任同中书门下三品）

• 陈叔达（626年任侍中）

• 封德彝（626年－627年任尚书右仆射）

• 宇文士及（626年－627年任中书令）

• 高士廉（626年－627年任侍中，638年-643年任尚书右仆射，643年-647年任同中书门下三品）

• 房玄龄（626年－629年任中书令，629年-643年、643年-648年任尚书左仆射）

• 长孙无忌（627年－628年任尚书右仆射，645年-649年摄侍中、检校中书令）

• 杜淹（627年－628年以吏部尚书参议朝政）

• 杜如晦（628年－629年任侍中，629年任尚书右仆射）

• 李靖（628年－629年任中书令，630年-634年任尚书右仆射）

• 王圭（628年-633年任侍中）

• 魏徵（629年－632年以秘书监参豫朝政，632年－638年任侍中，638年－642年以特进参议得失）

• 温彦博（630年－636年任中书令，636年-637年任尚书右仆射）

• 戴胄（630年－33年以民部尚书参豫朝政）

• 侯君集（630年－632年、632年－640年以兵部尚书参豫朝政，640年－643年以吏部尚书参豫朝政）

• 杨师道（636年－639年任侍中，639年－643年、645年任中书令）

• 刘洎（639年－644年以黄门侍郎参知政事，644年-645年任侍中）

• 岑文本（642年－644年以中书侍郎专典机密，644年-645年任中书令）

• 李世绩（643年－649年任同中书门下三品）

• 张亮（643年－646年以刑部尚书参豫朝政）

• 马周（644年－648年任中书令）

• 褚遂良（644年－647年以黄门侍郎参豫朝政，648年-649年任中书令）

• 许敬宗（645年同掌机务）

• 高季辅（645年同掌机务）

• 张行成（645年同掌机务）

• 崔仁师（648年以中书侍郎参知机务）

家庭

家世

唐太宗李世民的祖先

家族血统

唐皇室以李耳后裔自居，有出身陇西李氏与赵郡李氏两种说法，传统说法认为李唐皇室为汉人。在唐太宗时，曾有和尚法琳认为李唐先祖为拓跋氏之后，非李耳与陇西李氏后代，引起唐太宗不满，被唐太宗下狱。宋代朱熹与郑思肖以李唐闺门失礼家法缪戾，有李唐源自夷狄的说法。

其先祖李虎的兄弟名为起头与乞豆，非汉人名字，冯承钧与向达认为李唐家族有可能出身胡人。根据《新修本草》记载与唐太宗画相，严耕望推论李世民可能拥有胡人血统。刘盼遂与王桐龄考据认为李世民家族应为鲜卑拓跋氏后裔，这个说法曾引起讨论。美国学者陈三平与卓鸿泽皆认为李世民家族应出身于阿尔泰系民族，为胡人，与鲜卑拓跋部关系紧密。

根据唐朝先人曾被赐姓大野氏以及出身边镇等史实，日本学者金井之忠曾主张李渊家族可能出身高车叱李氏的假说，但遭陈寅恪驳斥。台湾学者刘学铫、常华安与中国学者苏日巴达拉哈等人，皆支持李唐家族先祖应出自高车。美国汉学者欧文·拉铁摩尔认为李世民家族具有突厥族血统。

陈寅恪认为李唐先世虽为汉人，但在李虎之后，其家族长期与胡人通婚，混有胡族血统，其祖母与其母亲皆出身鲜卑，李世民本人拥有胡族血统为明确事实。中华民国学者钱穆、萨孟武与岑仲勉等人皆有类似意见。日本学者冈田英弘认为，自五胡十六国时期之后，在中国北方，汉族与胡族大量混血，特别是在山西与河北一带，李世民家族出身在胡汉混血的北族之中。

妻妾

• 由于史料缺失，列出的后宫、姬妾诸人可能有重复。

皇后

• 文德皇后长孙氏，生废太子（恒山愍王）李承乾、濮恭王李泰、唐高宗李治，长乐公主、城阳公主、晋阳公主、新城公主。生于隋仁寿元年（公元601年），崩于贞观十年（公元636年），享年36岁。合葬昭陵地宫。喜爱读书，能劝谏太宗，著有《女则》。

妃

• 贵妃韦圭，北周太傅韦孝宽曾孙女，韦圆成女。生纪王李慎、临川公主李孟姜。尊封纪国太妃。生于公元597年，薨于公元665年，享年69岁。陪葬昭陵。与前夫李孝氏有一女，太宗封定襄县主。

• 杨贵妃：生赵王李福，封赵国太妃。生卒年不详。陪葬昭陵。

• 杨妃，隋炀帝女，生吴王李恪、蜀悼王李愔，生卒年不详。墓葬不明。

• 阴妃：阴世师之女。生齐王李佑。

• 燕德妃：燕宝寿女，隋观王杨雄外孙女。先封贤妃，后迁德妃。生越敬王李贞、江殇王李嚣。封越国太妃。生于隋大业五年（公元609年），咸亨二年（公元671年），享年63岁。陪葬昭陵。

• 郑贤妃，仅《唐会要》记载陪葬昭陵，目前尚无发现其墓葬。

• 贤妃徐惠，徐孝德女。生于武德八年（公元626年），由才人累进至二品充容。薨于永徽元年（公元650年），享年24岁。赠贤妃，陪葬昭陵石室。

嫔

• 昭仪某氏：生于隋仁寿元年（公元601年），薨于永淳元年八月二十四日（公元682年），享年81岁，十月十一日陪葬昭陵。现有昭陵墓志一方。

• 昭容韦尼子：韦孝宽曾孙女，韦匡伯长女，韦贵妃堂妹。生于隋大业三年（公元607年），薨于显庆元年九月八日长安崇圣宫，享年50岁，十月十八日陪葬昭陵。前夫王玄应。现有昭陵墓志一方。

• 下嫔某氏：豫章公主母。

世妇

• 婕妤某氏：生年不详，麟德二年卒，陪葬昭陵，墓志《大唐故婕妤三品亡尼墓志铭并序》。

• 杨婕妤：杨恭道第三女，生卒年不详，墓葬不明。

• 萧美人：萧铄第二女，生卒年不详，墓葬不明。

• 崔才人：崔宏道长女，生卒年不详，墓葬不明。

• 萧才人：萧铿第二女，生卒年不详，墓葬不明。

• 武才人（后来的武则天）：即唐高宗则天皇后武曌。武士获女。贞观时五品才人，后入感业寺。再入宫为高宗二品昭仪，进封为皇后，再后称帝。

其他妾室

• 巢剌王妃杨氏，原为齐王李元吉的王妃，玄武门之变后为太宗后宫，生曹恭王李明。有宠，太宗欲立为皇后，被魏徵劝阻。是否正式册封为妃嫔不详

• 刀人高惠通，李世民为秦王时的妾室

• 细人刀妙琏，李世民为秦王时的妾室

• 王帝释：生蒋王李恽

• 杨氏，隋朝尚书左右仆射、尚书令、司徒公、上柱国、楚国公杨素孙女，义阳郡太守、上柱国、清河郡开国公杨玄奖之女，唐朝宋州长史、兼虢王府司马、上轻车都尉杨崇本姐姐，与杨贵妃是否为同一人，无考。

• 某氏，庐江王妾。

女官、宫人

• 三品亡宫周氏：三品宫人，生卒年不详，陪葬昭陵。

• 三品亡宫金氏：武德八年（625年）出生，垂拱四年（688年）十一月二十六日卒，年六十四岁，永昌元年（689年）正月十三日陪葬昭陵，墓志《大唐故亡宫三品尼金氏之柩》

• 亡宫五品：五品宫人，姓名不详，生年不详，薨于显庆二年（657年）闰正月二十六昭陵宫，二月十四日陪葬昭陵。现有昭陵墓志一方。

• 三品亡尼：三品宫人，姓名不详，后出家为尼，生卒年不详，陪葬昭陵。

• 七品典灯：生卒年不详，姓名不详，陪葬昭陵。

子

唐太宗共有14位儿子：

• 李承乾：母长孙皇后。生于武德元年（公元618年），卒于贞观十九年（公元645年），年28岁。陪葬昭陵。常山郡王→中山郡王→皇太子→废太子→赠恒山愍王

• 李宽：母不详，早薨。生卒年不详。嗣楚王→赠楚王

• 李恪：母隋炀帝女杨妃。生于武德二年（公元619年），薨于永徽四年二月（公元653年），享年34岁。赠司空，墓葬不详。长沙郡王→汉王→蜀王→吴王→废为庶人→赠郁林郡王→吴王

• 李泰：母长孙皇后。生于武德三年（公元620年），永徽三年（公元652年）薨于郧乡县，时年33岁。赠太尉、雍州牧，葬于薨地。宜都郡王→卫王→越王→魏王→东来郡王→顺阳郡王→濮恭王

• 李佑：母阴妃，生年不详，卒于贞观十七年（公元645年）。墓葬不详。宜阳郡王→楚王→燕王→齐王→废为庶人

• 李愔：母隋炀帝女杨妃。生年不详，乾封二年（667年）卒于流配地巴州。赠益州大都督，陪葬昭陵。梁王→蜀王→贬为庶人→涪陵郡王→蜀悼王

• 李恽：母王氏，生年不详，薨上元年间。赠司空、荆州大都督，陪葬昭陵。郯王→蒋王

• 李贞：母燕德妃。生于武德八年（公元626年），薨于垂拱三年（公元688年），享年62岁。陪葬昭陵。汉王→原王→越敬王

• 李治：母长孙皇后。晋王→皇太子→唐高宗

• 李慎：母韦贵妃，生年不详，薨于永昌元年（公元689年）。陪葬昭陵。申王→纪王

• 李嚣：母燕德妃，早薨。生年不详，卒于贞观六年正月（公元633年）。江殇王

• 李简：母不详，早薨。生年不详，卒于贞观五年四月（公元632年）。代王

• 李福：母杨贵妃。生于贞观八年（公元635年），薨于咸亨元年（公元670年），赠司空、并州都督，陪葬昭陵。赵王

• 李明：母李元吉妻巢剌王妃杨氏。生卒年不详。陪葬昭陵。曹恭王

女

《新唐书》记唐太宗共有21位女儿，出生顺序见于个人记载：

• 襄城公主，长女：母不明，下嫁萧锐。生年不详。陪葬昭陵。

• 汝南公主：第三女，母不明，早薨。生卒年不详。墓葬不详。

• 南平公主：母不明，下嫁王敬直，以累斥岭南，更嫁刘玄意。生卒年不详。陪葬昭陵。

• 遂安公主：母不明，下嫁窦逵，逵死，又嫁王大礼。生卒年不详。陪葬昭陵。

• 长乐公主李丽质，第五女：母长孙皇后，下嫁长孙冲。生于武德四年（公元621年），薨于贞观十七年（公元643年）八月十日，享年23岁。陪葬昭陵。

• 豫章公主：母宫中下嫔，下嫁唐义识。生卒年不详。陪葬昭陵。

• 巴陵公主：母不明，下嫁柴令武，生年不详，薨于永徽四年二月。墓葬不详。

• 普安公主：母不明，下嫁史仁表，生卒年不详，陪葬昭陵。

• 东阳公主：母不明，下嫁高履行，生卒年不详，陪葬昭陵。

• 临川公主，第十一或第十二女：表字「孟姜」，母韦贵妃，下嫁周道务。生于武德七年（公元624年），卒于永淳初年（公元682年），享年58岁。陪葬昭陵。

• 清河公主：名「敬」，表字「德贤」，母不明，下嫁程怀亮。生于武德七年（公元624年），卒于麟德元年（公元664年），享年41岁。陪葬昭陵。

• 兰陵公主，第十九女：名「淑」，表字「丽贞」，母不明，下嫁窦怀悊。生年不详，病逝于唐高宗显庆三年（公元658年）八月。陪葬昭陵。

• 晋安公主：母不明，下嫁韦思安，又嫁杨仁辂，生卒年不详。陪葬昭陵。

• 安康公主：母不明，下嫁独孤谋。生卒年不详。陪葬昭陵。

• 新兴公主：母不明，下嫁长孙曦。生卒年不详。陪葬昭陵。

• 城阳公主：母长孙皇后，下嫁杜荷，又嫁薛瓘。生卒年不详。陪葬昭陵。

• 高阳公主：母不明，下嫁房遗爱。生年不详，薨于永徽四年二月。墓葬不详。

• 金山公主：母不明，早薨。生卒年不详。墓葬不详。

• 晋阳公主：表字「明达」，母长孙皇后，未及下嫁。生卒年不详，薨年十二。墓葬不详。

• 常山公主：母不明，生卒年不详。没有下嫁。墓葬不详。

• 新城公主：母长孙皇后，初嫁长孙诠，后嫁韦正矩。生年不详，薨于龙朔三年。陪葬昭陵。

继女

• 定襄县主李氏，韦贵妃与前夫李孝氏所生之女，嫁阿史那忠。

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