李建成
By 626, Li Shimin was locked in an intense rivalry with his older brother Li Jiancheng, who was the Crown Prince. He feared that Li Jiancheng would kill him. Hou, along with Li Shimin's brother-in-law Zhangsun Wuji, Zhangsun's uncle Gao Shilian, and the general Yuchi Gong, advised Li Shimin to act first and ambush Li Jiancheng and another brother who supported Li Jiancheng, Li Yuanji the Prince of Qi. Li Shimin agreed, and in 626 ambushed Li Jiancheng and Li Yuanji, killing them. During the subsequent battles between Li Shimin's forces and Li Jiancheng's and Li Yuanji's forces, Hou led Li Shimin's forces. Following these battles, Li Shimin effectively forced Emperor Gaozu to make him the crown prince, and then to yield the throne to him (as Emperor Taizong).