 With Yang Tong's regime having fallen earlier that year when Yang Tong's official Wang Shichong forced Yang Tong to yield the throne to him, ending Sui and establishing a new state of Zheng, Du decided to submit to Tang Dynasty.Emperor Gaozu of Tang commissioned Du as the commandant of He Prefecture (i.e., Liyang) and the commander of the forces south of the Huai River.He also continued to have Du hold the title of Prince of Chu.