The change of Xuanwumen was a bloody coup at the North Palace Gate of the Inner Palace by General Ce Tian and Li Shimin, the second son of Tang Gaozu's second son Li Yuan, on the fourth day of June (July 2, AD 626) in Wude, the capital of Chang 'an (now Xi 'an City, Shaanxi Province) in the Tang Dynasty.

After Tang Gaozu acceded to the throne, Li Jian was the prince, Li Shimin was the king of Qin, and Li Yuanji was the king of Qi. Of these three people, Li Shimin contributed the most. Jinyang arise, is his idea; In the next few battles, he also made the greatest achievements. Li Gonggong was inferior, and only because he was the eldest son of Gaozu did he get the position of Prince.

Prince built himself to know the prestige ratio.