Around the new year 398, with Tuoba Gui ready to attack Yecheng, Yecheng's defender Murong De abandoned it and fled south of the Yellow River, to Huatai (滑台, in modern Anyang, Henan), where he declared an independent Southern Yan state. With resistance north of the Yellow River largely gone, Tuoba Gui left Tuoba Yi and Suhe Ba () as viceroys over the former Later Yan territory, and returned to Shengle. In order to enhance communications and control, Tuoba Gui constructed a highway between Wangdu (望都, in modern Baoding, Hebei) and Dai (代, in modern Zhangjiakou, Hebei), over the Taihang Mountains. He soon, however, recalled Tuoba Yi to be his prime minister and replaced him with his cousin Tuoba Zun () the Duke of Lueyang.