After the Yang Wengan incident, Li Jiancheng regarded Li Shimin as a thorn in the flesh, and did everything possible to kill him.

Li Jiancheng and Li Yuanji took advantage of the forbidden palace to bribe the harem concubines and let them say that they were good and bad things about Li Shimin.

Li Yuan saw that the three sons were getting more and more troublesome, so he ordered Li Shimin to live in the Chengqian Palace, and Li Yuanji to live in the backyard of Li Yuan's bedroom in the Wude Palace, so that the three brothers were under their noses. This did not ease the relationship between the three brothers.

The harem concubines have never bribed them over the years, and the requirements they put forward, Li Shimin is also official, and now the three brothers are in the forbidden palace, Li Jiancheng and Li Yuanji are very popular, and they stay away from Li Shimin.

Li Jiancheng privately recruited more than 2,000 warriors, known as Changlin soldiers, and secretly borrowed 300 Youyun elite cavalry from Luo Yi and stationed them in various cities of the Prince's Mansion.

The year 626 was quickly reached. In this year, 30,000 Turks broke into the Great Wall and surrounded the border city of Wucheng. Li Jiancheng suggested to Li Yuan: "Erchen recommends the third brother to lead the army. ”

Li Yuan quickly agreed to Li Jiancheng's suggestion, and ordered Li Yuanji, the king of Qi, to replace Li Shimin to lead the northern expedition of all armies and horses, and ordered Wei Chigong, Cheng Yanjin, Duan Zhixuan, Qin Qiong and others to go on the expedition together, and the elite of the Qin Wangfu was also emptied. At the same time, in order to alleviate the contradictions between his three sons, Li Yuan sent a letter to Gao Buer and asked him to come to Chang'an.

Before the expedition, Li Jiancheng said to Li Yuanji: "Now you have obtained the generals of the Qin Wangfu and 60,000 elite soldiers, and when you set out on the expedition the day after tomorrow, I and the King of Qin will serve you, and when the time comes, you will act at the opportunity and take the opportunity to kill Li Shimin." When the time comes, I will tell my father that he has died of a violent illness, and I will invite him to a banquet tonight, and I will order someone to do something in his wine. ”

Li Yuanji nodded in agreement, and said with a fierce glint in his eyes: "As long as Li Shimin dies, the soldiers and horses of Tiance Mansion will be leaderless, and then I will force my father to pass on the throne to you, so that the world will be decided." ”

Who knew that Li Shimin had already bought off the prince's mansion and changed the rate to Wang Zhi, and Li Jiancheng's words were listened to by Wang Zhi, so he told Li Shimin.

When the generals of Tiance Mansion heard what Li Shimin said, they were immediately furious and advised Li Shimin to strike first.

Li Shimin said: "Fratricidal cannibalism has been a heinous crime since ancient times, and I also know that disaster is coming, but I can't bear to kill them first, so let's wait for them to do it." ”

The eldest grandson Wuji said: "Then will you go to the prince's mansion for a banquet tonight?" ”

"Of course we go, otherwise we will disturb them and make them attack in advance, and we will be passive."

Qin Qiong said: "When the time comes, I will accompany you with Jingde." ”

The eldest grandson Wuji said: "The chain soft armor should also be put on, and Duan Zhixuan and I will lead the people to meet outside the mansion in case of accidents." ”

Li Shimin agreed one by one.

Li Shimin took Qin Qiong and Wei Chigong to the Prince's Mansion, Li Yuanji was also there, the three of them talked about homely words, the atmosphere was harmonious, and soon the banquet was over, Li Shimin returned to the Qin Palace, and immediately felt unwell and diarrhea. When I found Lang Zhong, he was still poisoned, but it was a chronic poison that would attack after two days, but fortunately, the poisoning was not deep, and he was saved.

After leaving the ghost gate, Li Shimin felt that there was no possibility of reconciliation between himself and the two brothers, so he immediately made up his mind to prepare to capture and kill them.

After Li Yuan entered the palace, out of trust in Gao Buer, it was the Xuanjia Army led by Duan Zhixuan who served as the marcher, and Li Shimin ordered Duan Zhixuan to lead his troops to ambush at Xuanwu Gate tomorrow, and take advantage of tomorrow morning to capture and kill the two of them.

Li Shimin entered the palace that night to meet Li Yuan, and made it clear that the brothers were harming each other, Li Yuan saw that it was getting late, and appeased Li Shimin and asked him to go back, and wait for tomorrow morning to ask the palace to understand.

This matter was secretly told to Li Jiancheng by Li Yuan's concubine Zhang Jieyu, Li Jiancheng immediately found Li Yuanji to discuss countermeasures, Li Yuanji said: "Since you have already exposed your feet, then simply don't do it, you take the prince and the guard, I take the pro-army, we have three or four thousand people, enter the palace tomorrow to control my father, and then send someone to replace the Xuanwumen defenders, and wait for Li Shimin to capture him immediately." ”

Li Jiancheng immediately agreed.

Early the next morning, Li Shimin took his eldest grandson Wuji, Wei Chigong, Fang Xuanling, Du Ruhui, Yu Wenshiji, Gao Shilian, Hou Junji, Cheng Yanjin, Qin Qiong, Duan Zhixuan, Qu Tutong, Zhang Shigui and others into the court, and laid an ambush at Xuanwu Gate.

Li Jiancheng and Li Yuanji didn't know it, and they also entered the court with soldiers and horses.

In the palace, Li Yuan also summoned Pei Lian, Xiao Yu, Chen Shuda and others early, preparing to investigate Li Jiancheng's poisoning of Li Shimin in the court.

When the three brothers came to Xuanwu Gate, Li Jiancheng felt different, today the defenders of Xuanwu Gate were three or four times more than usual, there were three or four thousand people, so he shouted angrily: "Duan Zhixuan, do you want to rebel?" Dare to send additional palace guards without authorization. So he ordered someone to capture Duan Zhixuan, and taking advantage of the chaos, Li Yuanji gave up a sword towards Li Shimin.

As soon as Li Shimin saw them move, he immediately ordered his subordinate generals to take action, and the Xuanjia army quickly joined the battle on the grounds of quelling the chaos, and soon, Li Jiancheng's men and horses were controlled, and Li Jiancheng and Li Yuanji were also captured by Qin Qiong and Wei Chigong.

Li Shimin said to the two: "You and I are brothers, why bother to die several times." ”

Li Jiancheng said: "You and I are each other, if you become a king or lose, if you want to kill, you will scrape you." ”

Li Yuanji cried: "Second brother, I am innocent, it was the eldest brother who asked me to do this, I beg the second brother to forgive me, I want to see my father." ”

Li Jiancheng said: "Ask him to do something." ”

Li Shimin said to Li Yuanji: "I didn't see you being merciful when you shot a cold arrow at me just now. He glanced at the generals and cut off the heads of the two, and then Li Shimin went to see Li Yuan.