He was allied with his second younger brother Prince Li Yuanji. In Chang'an, Crown Prince Li Jiancheng was increasing his power by recruiting more than two thousand men to serve in the Changlin troops, which he stationed at the East Palace near the Changlin Gate. He mostly relied on Luoyang where he could successfully build strong support among military and civil officials. Prince Li Shimin found himself unable to gain support in the capital Chang'an or inside the imperial palaces, as he was often away on military expeditions.

Henceforth, Li Jiancheng attempted to undermine Li Shimin by getting his staff members removed and reassigned to other posts. This may have insinuated in Li Jiancheng's mind that Li Shimin could harbor ambition to ascend to the throne himself. In 621, he established the College of Literary Studies comprising a staff of eighteen scholars, who served as his advisors on state affairs. There, Li Shimin established himself and appointed about fifty civil and military officials, which made it possible for him to challenge the heir apparent's pre-eminence. He placed Li Shimin in charge of the civil and military administration of the eastern plain, with Luoyang as its headquarters. Eventually, Emperor Gaozu elevated Li Shimin's position above all other nobles. Meanwhile, Li Jiancheng was stationed along the northern frontier to guard it against the Tujue, which left him unable to build up a similar reputation. He had led the attack on Dou Jiande and Wang Shichong, whom he defeated in battle, which gained him prestige among his contemporaries. For instance, Li Shimin was instrumental in defeating several of Tang's major rivals. About two months later, Emperor Gaozu abdicated and passed the throne to Li Shimin, who would become known as Emperor Taizong.Īfter the founding of the Tang dynasty by Emperor Gaozu, the emperor's eldest son Li Jiancheng was established as the heir apparent, but he was often overshadowed by his younger brother Li Shimin. Within three days after the coup, Li Shimin was installed as the crown prince. There, Li Jiancheng and Li Yuanji were murdered by Li Shimin and his men. He took control and set up an ambush at Xuanwu Gate, the northern gate leading to the Palace City within the imperial capital Chang'an. Li Shimin, the second son of Emperor Gaozu, was in an intense rivalry with his elder brother Li Jiancheng and younger brother Li Yuanji. The Xuanwu Gate Incident was a palace coup for the throne of the Tang dynasty on 2 July 626, when Prince Li Shimin (Prince of Qin) and his followers assassinated Crown Prince Li Jiancheng and Prince Li Yuanji (Prince of Qi). Emperor Gaozu eventually abdicates in favor of Prince Li Shimin.Prince Li Shimin becomes heir to the imperial throne.Prince Li Shimin and his close followers gain complete control of the Tang government.Successful coup d'état by Prince Li Shimin Palace City, East Palace, and Forbidden Park in and around Chang'an, China

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