Liu Wuzhou
When Liu Wuzhou rose against Sui rule in spring 617 at Mayi (馬邑, in modern Shuozhou), declaring himself Dingyang Khan, Yuchi Jingde joined Liu and was made a general. In 619, he served under Liu's major general Song Jingang (宋金剛) in attacking Tang Dynasty territory to the south. Around the new year 620, Yuchi and another general under Song, Xun Xiang (尋相), engaged the Tang general Li Xiaoji (李孝基) the Prince of Yong'an (Emperor Gaozu of Tang's distant nephew), defeating Li Xiaoji and capturing not only him, but several other key Tang officials, including Emperor Gaozu's cousin Dugu Huai'en (獨孤懷恩), Yu Yun (于筠), Tang Jian (唐儉), and Liu Shirang (劉世讓). However, when Yuchi and Xun then engaged the forces under the major Tang general Li Shimin the Prince of Qin (Emperor Gaozu's son), they were defeated first by Yin Kaishan and Qin Shubao, and then Li Shimin himself, escaping just with their lives. Subsequently, at the suggestion of the captured Tang Jian, Yuchi released Liu Shirang in order to negotiate peace with Tang, but those negotiations appeared to go nowhere at the moment. In summer 620, after Li Shimin achieved further victories against Song, forcing Liu Wuzhou to flee, Li Shimin sent his cousin Li Daozong the Prince of Rencheng and Yuwen Shiji to persuaded Yuchi and Xun to surrender, and they did. Li Shimin, who was impressed by Yuchi's battle prowess, was happy about this development and put Yuchi, as well as the 8,000 soldiers who surrendered with him, directly under his own command, against the misgivings of the general Qutu Tong (屈突通), who feared that Yuchi was not truly submitting.