Liu Heita
Later in 621, Dou's general Liu Heita, supported by a group of Dou Jiande's supporters angry that Tang had executed Dou Jiande (even though he had previously treated the Tang prince Li Shentong (李神通) and the Princess Tong'an (Emperor Gaozu's sister) with kindness when he captured them), rose against Tang rule, and quickly captured most of Dou's former territory. In doing so, he was in communication with Xu, and Xu also rose, capturing the Tang general Sheng Yanshi (盛彥師) and receiving support from eight prefectures. He ordered Sheng to write a letter to Sheng's brother, who was the county magistrate of Yucheng (虞城, in modern Shangqiu, Henan), to get Sheng's brother to surrender, but Sheng instead wrote a letter that told his brother to be faithful and not betray Tang. Xu, after seeing the letter, laughed and said, "General Sheng has integrity and honor, and I shall not kill him." Liu gave Xu a general title, and in winter 621, Xu claimed the title of Prince of Lu as well.