After the founding of the Tang Dynasty, Li Jiancheng was created the heir apparent. Even though Li Jiancheng was designated as the heir apparent, he was often overshadowed by his younger brother Li Shimin. Li Shimin was instrumental in defeating several of Tang’s major rivals. He had led the attack on Dou Jiande and Wang Shichong, whom he defeated in battle, which gained him prestige amongst his contemporaries. 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. Eventually, Emperor Gaozu elevated Li Shimin’s position above all the other nobility. He also placed Li Shimin in charge of the civil and military administration of the eastern plain with Luoyang as its headquarters. 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. In 621, he established…