 Dou agreed and sent messengers to Wang, promising support, while sending his official Li Dashi to Li Shimin, requesting that he end his campaign against Luoyang.Li Shimin, however, detained Li Dashi and did not respond.Dou then merged the troops from Meng Haigong and Xu Yuanlang (whom he had defeated earlier as well) and headed from Meng's headquarters at Cao Prefecture (in modern Heze as well) toward Luoyang, joining forces with the Zheng general Guo Shiheng (), and he defeated several cities held by Tang.