 After Wang defeated Li in 619, Xu submitted to the Sui emperor Yang Tong, then at Luoyang, although he also offered submission to Emperor Gaozu of Tang and was created the Duke of Lu.After Wang had Yang Tong yield the throne to him later that year, ending Sui and establishing a new state of Zheng, Xu also nominally submitted to Zheng.In winter 619, after another rebel leader, Dou Jiande the Prince of Xia, conquered the Tang territory north of the Yellow River, Xu submitted to Xia.