 By this point, the territory north of the Yellow River and east of the Taihang Mountains were largely his, save for those under the control of Luo Yi (who had now taken the name Li Yi, having been granted the imperial surname of Li by Tang's Emperor Gaozu) and Gao Kaidao.In winter 619, Li Shiji considered fleeing to Tang territory, but was fearful that Dou would execute his father Li Gai, and therefore attacked Zheng to gain Dou's trust.In one of the battles against Zheng, Li captured the Zheng army officer Liu Heita, whom Dou was impressed with and created the Duke of Handong.