Biography
Family Background and Early Life
Li Jiancheng was born in 589 as the eldest legitimate son of Li Yuan, Duke of Tang, and Lady Dou. The Li family descended from Li Hu, one of the Eight Pillars of State of Western Wei, and held the hereditary title Duke of Tang, occupying a prominent place among the Guanzhong aristocratic elite. During Li Jiancheng's youth, Li Yuan successively served as inspector of Qiao, Long, and Qi prefectures, and the family moved with him. In 613 Li Yuan became Vice Minister of the Court of the Imperial Stud and later an inspector and suppression commissioner in Hedong. In 614 the twenty-six-year-old Li Jiancheng married Zheng Guanyin of the elite Zheng clan of Xingyang, a marriage that helped broaden the family's ties in the eastern aristocratic world.
In 615 Li Yuan became Taiyuan garrison commander while Li Jiancheng lived with his household in Hedong. As the Sui order collapsed, Li Yuan secretly prepared an uprising. According to the *Diary of the Founding of the Great Tang*, he ordered Li Jiancheng to “secretly connect with talented men” in Hedong, while Li Shimin was to “secretly recruit bold companions” at Jinyang. Li Jiancheng therefore spent this period building ties with local elites and men of talent in preparation for revolt.
The Jinyang Uprising and Capture of Chang'an
In early 617 Liu Wuzhou rebelled at Mayi, captured Loufan, and occupied Fenyuan Palace. Li Yuan recruited troops at Taiyuan under the pretext of suppressing rebels and secretly summoned Li Jiancheng from Hedong. In June Li Jiancheng and Li Yuanji took back roads to Taiyuan; their younger brother Li Zhiyun was captured and killed by Sui forces. Once Li Jiancheng arrived, Pei Ji, Liu Wenjing, and others joined him in urging Li Yuan to rise, invoking precedents of deposing incapable rulers and proposing that Emperor Yang be removed, Prince Dai Yang You installed, a righteous army raised, and the movement given political legitimacy. Li Yuan accepted the proposal and formally began the uprising.
Li Yuan sent Li Jiancheng and Li Shimin to take Xihe. The newly raised soldiers were undisciplined, so Li Jiancheng established military regulations. On the march he shared hardship with the troops, required payment for local produce, and politely refused gifts. At Xihe he personally called on the city to surrender. Only commandery assistant Gao Deru resisted. After Zhu Zhijin enabled the army to enter, Gao was captured and executed while the rest were pardoned. The round trip took only nine days. Li Yuan praised the operation and created Li Jiancheng Duke of Longxi and Left Commander-in-Chief.
Later that summer, Li Jiancheng advised advancing on Huoyi after the rains. When Li Yuan worried that Song Laosheng would remain behind the walls, Li Jiancheng argued that Song was brave but lacked judgment and could be provoked into battle. Li Yuan adopted the plan. Li Jiancheng and Li Shimin led the left and right wings in feigned attacks, cut the enemy's retreat, and helped take Huoyi. The *Old Book of Tang* preserves a different version in which Li Yuan and Li Jiancheng were initially driven back and Li Jiancheng fell from his horse before Li Shimin reversed the battle; the two records therefore differ.
In September Li Jiancheng led Liu Wenjing, Wang Changxie, Jiang Baoyi, and tens of thousands of troops to Tong Pass and Yongfeng Granary to block Qutu Tong. After Qutu Tong's western route was cut, Li Yuan ordered Li Jiancheng to choose elite troops at Yongfeng and hurry toward the Changle detached palace. In October Li Yuan reached Bashang and joined Li Jiancheng and Li Shimin, bringing the army above 200,000. During the assault on Chang'an, Li Jiancheng attacked from the east and south while Li Shimin attacked from the west and north. The city fell in November.
Period as Crown Prince
After Chang'an fell, Li Yuan installed Yang You as emperor and became Prince of Tang. Li Jiancheng was named heir apparent to the Prince of Tang and given an official staff. In early 618 he became General-in-Chief for Pacification and Commander of the Eastern Expedition, leading 70,000 troops toward Luoyang. Supply problems forced a return in the fourth month, after which he was appointed Prefect of the Masters of Writing.
When Li Yuan founded the Tang in May 618, Li Jiancheng became Crown Prince. He assisted with government and repeatedly led campaigns. In 619 he suppressed Zhu Shanhai at Sizhu with General Sang Xianhe, then went to Yuan Prefecture to receive An Xinggui and Hexi after Li Gui's capture. In 620 he guarded Pu Prefecture against the Turks. In 621 he defeated the Ji Hu leader Liu Xiancheng in Fu Prefecture. After inducing a number of Hu leaders to surrender, he feared renewed disorder and ordered the execution of more than 6,000 surrendered troops when the plan became known and Liu Xiancheng fled to Liang Shidu.
When Liu Heita rebelled again in 622, Li Jiancheng accepted advice from Wei Zheng and Wang Gui and requested command. Wei Zheng proposed replacing the coercive policies used in earlier campaigns with leniency toward captives and families. Li Jiancheng followed the recommendation, released prisoners, and spread word that captured wives and children were being freed. This helped dissolve Liu Heita's support. Liu was captured at Raoyang in early 623, and Shandong was pacified.
Succession Struggle and the Xuanwu Gate Incident
As unification neared completion, rivalry between Li Jiancheng and Li Shimin intensified. Li Shimin had accumulated enormous military prestige through campaigns against Wang Shichong, Dou Jiande, and others, while the Prince of Qin's headquarters drew many talented civil and military officials. Li Jiancheng remained Crown Prince but faced a powerful rival. In 624, the Yang Wengan Incident implicated the Eastern Palace in an illicit transfer of arms. Li Yuan was furious and for a time reportedly promised the succession to Li Shimin, but withdrew the idea after remonstrance and instead exiled two of Li Jiancheng's officials, Wang Gui and Wei Ting. The episode deepened mistrust.
The Eastern Palace and the Prince of Qin's establishment then competed openly. Li Jiancheng allied with Li Yuanji, Prince of Qi, and repeatedly attacked Li Shimin politically before Li Yuan. In 626, when the Turks threatened the frontier, Li Jiancheng recommended Li Yuanji to command in Li Shimin's place and transferred elite troops from the Prince of Qin's establishment to the Qi prince, further weakening Li Shimin. Zhangsun Wuji, Fang Xuanling, Du Ruhui, and others urged Li Shimin to act first. On the fourth day of the sixth month, Li Shimin ambushed the Xuanwu Gate. Li Jiancheng and Li Yuanji realized something was wrong as they entered the palace. Li Shimin shot Li Jiancheng and Yuchi Jingde killed Li Yuanji. Li Jiancheng's five sons—Li Chengdao, Li Chengde, Li Chengxun, Li Chengming, and Li Chengyi—were also killed, and many Eastern Palace officials were executed or exiled. Li Jiancheng was thirty-seven.
His Achievement at the Rising of Jinyang: Xihe and Huoyi
When Li Yuan was made defender of Taiyuan in 617, Li Jiancheng was with the family at Hedong, and his father ordered him to make secret friends among men of ability there. The Record of the Founding of the Great Tang says of this that "the crown prince was then at Hedong, and only the prince of Qin attended him, and he was ordered to seek out the outstanding secretly at Hedong while the prince of Qin secretly gathered bold friends at Jinyang." In the same year Liu Wuzhou rose in revolt and called himself son of heaven, took the Loufan commandery in the third month and occupied the Fenyuan palace; Li Yuan, on the one hand, raised troops in the name of suppressing the rebels, and on the other sent secret messengers to Hedong urging Li Jiancheng to come to Taiyuan; on the sixth day of the sixth month Li Jiancheng and the prince of Qi, Li Yuanji, arrived from Hedong, at which Li Yuan "was greatly pleased," and Pei Ji and the others then petitioned through the crown prince and the prince of Qin that, after the precedents of Yi Yin's deposing Tai Jia and Huo Guang's deposing the duke of Changyi, the emperor be deposed and the prince of Dai set up, "raising righteous troops and proclaiming it to the commanderies and counties, and changing the banners to show the Turks," so that the enterprise should have a name.
The first hard fight after the rising was at Xihe. Its commander had repeatedly declared his loyalty to the Sui and blocked Li Yuan's road west, and on the fifth of the sixth month Li Yuan sent Li Jiancheng and Li Shimin against him with only three days' rations. Li Jiancheng, seeing that the newly raised troops were untrained and fearing they could not fight, laid down military law and set the army in order; on the march he shared hardship with his men — "fruits and vegetables by the roadside were not eaten unless paid for," and if one of the troops stole, he sent to find the owner and pay him without exposing the thief; when elders offered food and drink he "took their meaning to heart" and divided it equally among the soldiers in his sight, never taking it alone; and when cattle and wine were sent he thanked the givers and dismissed them with the words, "This is the Sui law; I do not dare." Reaching Xihe, the two brothers went unarmoured to proclaim their purpose, and all outside who wished to enter the city were let in "without distinction of sex or age," so that those within, seeing such forbearance, "all wished to run to them," and only the commandery assistant Gao Deru stood stubbornly out; Zhu Zhijin, the judicial clerk, let the troops in from the wall and brought Gao Deru out, and the brothers, counting his offences — he was the man who had once "seen a phoenix" in a wild bird and flattered the Sui ruler with an omen, "like Zhao Gao calling a deer a horse" — had him beheaded, "and beyond him not one man was killed, not a hair harmed." The whole expedition took nine days, and Li Yuan, hearing of it, said with delight, "Making war in this way, a man may traverse the world," and on that day fixed the plan of entering the passes, making Li Jiancheng duke of Longxi and grand commander of the left guard, with the three left armies under him.
The battle of Huoyi was another key action on the way into the passes. Song Laosheng would not come out, and Li Jiancheng and Li Shimin advised: "Laosheng comes of humble stock, brave but without wisdom, and has some name for hunting down small bandits. Coming here, he will expect great reward; if he does not fight he will certainly die. Tempt him with light horse and he will surely come out." Li Yuan therefore took several hundred light horse to within five or six li east of Huoyi to wait for the infantry, and "dividing his men into a dozen squadrons, rode about the southeast and southwest of the city, pointing and signalling as if to camp and attack," sending Yin Kaishan to hurry up the rear. Song Laosheng, seeing the rear approaching, thought they meant to camp under the walls and came out by the south and east gates with some thirty thousand men. Li Yuan, fearing he would not fight far from the city, formed his cavalry into left and right, Li Jiancheng commanding the left to hold the east gate and Li Shimin the right to cut the road to the south gate, "and ordered a slight withdrawal, feigning avoidance"; Song, seeing the retreat, thought Li Yuan afraid and advanced more than a li from the city and formed up. Then "the emperor ordered the two elder sons, as arranged, to gallop for the gates," and the troops came on shouting, so that "before the drums moved, the blades had met, with a noise like a mountain falling and the gate towers shaking"; Li Yuan spread word that Song Laosheng was beheaded, his men broke and fled for the gates, which the brothers already held with the portcullis down, and Song, climbing a rope let down from the wall, was cut down by Lu Jun'e's men and his head sent to Li Yuan. A variant account appears in the Old History's annals of Taizong: that "Li Yuan and Li Jiancheng formed east of the city and Taizong with Chai Shao south of it; Laosheng came on fast against Li Yuan, Li Jiancheng fell from his horse and the enemy pressed him, so that both Li Yuan's and Li Jiancheng's troops gave way, until Taizong came down the steep bank from the southern plain with two horsemen, broke the enemy's line and beat them utterly." Both accounts survive, and in both Li Jiancheng stands in the front line at Huoyi. On entering the passes Li Yuan sent the heir with Liu Wenjing and Wang Changxie to hold the Yongfeng granary and Tong pass, where the Sui general Qutu Tong was blocked by Liu Wenjing, "unable to go east and with no road west"; and he ordered Li Jiancheng to pick troops from the Yongfeng garrison and march by way of Xinfeng to the Changle detached palace, until in the tenth month Li Yuan reached Bashang, "joining the armies of the dukes of Longxi and Dunhuang, more than two hundred thousand men," and in the assault on the capital "the east and south faces were the duke of Longxi's and the west and north the duke of Dunhuang's."