Liu Wuzhou
Li Shimin crossed the Yellow River, and while he initially had problem with food supplies, he was able to persuade the people in the country to supply his army. He then refused to engage Song, trying to wear Song down. Meanwhile, however, another Tang army, commanded by Emperor Gaozu's cousin Li Xiaoji (李孝基) the Prince of Yong'an, assisted by another cousin, Dugu Huai'en (獨孤懷恩) and two other officials, Yu Yun (于筠) and Tang Jian (唐儉), was attacking Liu's ally Lü Chongmao (呂崇茂), then at Xia (夏縣, in modern Yuncheng, Shanxi). Lü sought aid from Song, and Song sent his subordinates Yuchi Gong and Xun Xiang (尋相) to attack Li Xiaoji, defeating him, and capturing him, Dugu, Yu, Tang, as well as another key general, Liu Shirang (劉世讓). (Liu Xiaoji soon tried to flee and was executed by Liu Wuzhou.) When Yuchi and Xun then sought to aid another ally, Wang Xingben (王行本), a Sui general still holding out against Tang at Pufan (蒲反, in modern Yuncheng as well), but they were defeated by Li Shimin and forced to withdraw; Wang subsequently was forced to surrender in spring 620, and Emperor Gaozu executed him. Later in spring 620, Liu Wuzhou attacked Tang's Lu Prefecture (潞州, roughly modern Changzhi, Shanxi), and while he was initially successful, he was unable to capture its capital.