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).
Li Shimin agreed, and in 626 launched a preemptive assault on Li Jiancheng and Li Yuanji, killing them. Subsequently, Hou led Li Shimin's forces, and Li Shimin ultimately compelled Emperor Gaozu to appoint him crown prince and then relinquish the throne to him (as Emperor Taizong).