In 629, Emperor Taizong commissioned the general Li Jing to lead a major expedition against Eastern Tujue, and in 630, Li Jing captured Ashina Duobi and effectively destroyed Eastern Tujue. Much of the Eastern Tujue people surrendered to Xueyantuo, and some surrendered to Tang. After this event, Xueyantuo was the predominant power north of China, but remained formally submissive to Tang. In 638, Emperor Taizong, with Yi'nan's concurrence, further created Yi'nan's sons Bazhuo and Jialibi () as subordinate khans under Yi'nan-ostensibly to honor them, but hoping to create dissension between them. In 639, when Emperor Taizong commissioned the general Hou Junji to launch a campaign against Gaochang, Yi'nan offered to attack Gaochang at the same time, although Hou's quick conquest of Gaochang appeared to involve no actual Xueyantuo aid.