[3] Pei Ju had become apprehensive that the khagan was becoming strong and difficult to control and had therefore suggested that Emperor Yang offer to marry a princess to the khan's brother Ashina Chiji (阿史那叱吉).
In the fall of 615, when Emperor Yang was visiting Yanmen Commandery on the northern frontier, the khagan launched a surprise attack on the area, overrunning most of its Chinese settlements.
During the turmoil of the later years of Yangdi's reign, he supported various local warlords in northwestern China, who claimed the title of emperor, including Li Yuan, who would go on to find the Tang dynasty.
The khagan supplied Li with 2,000 horses and 500 cavalry, who played a crucial role in the early victories of the Tang such as the Battle of Huoyi.
When khagan asked him what Li Yuan's intention was, Liu responded: Commander of Wuyuan county Zhang Cangxun (张长逊) submitted to Shibi Qaghan in 618 and was created Koli Tegin.
[7] In February 619, Shibi Khagan was planning to launch a major incursion into Chinese territory and he had Liu Wuzhou to join him.