In winter 641, believing that Emperor Taizong was about to carry out sacrifices to heaven and earth at Mount Tai and would be unable to aid the Eastern Turks, Yinan launched a major attack on them, commanded by his son Dadu (). Li Simo was forced to retreat inside the Great Wall. Emperor Taizong commissioned Li Shiji, assisted by Zhang Jian (), Li Daliang, Zhang Shigui (), and Li Xiyu (), to attack Xueyantuo. Li Shiji soon defeated Dadu at Nuozhen River (, flowing through modern Baotou, Inner Mongolia), and Dadu fled.