In 398, against Murong Sheng's and Murong Nong's advice, Murong Bao insisted on launching another campaign to try to regain territory lost to Northern Wei, putting Murong Sheng in charge of Longcheng as he departed. The tired troops mutinied on the way, forcing him to return to Longcheng to defend it with Murong Sheng, but when Murong Nong then inexplicably surrendered to the rebels, Longcheng fell, and Murong Bao and Murong Sheng were forced to flee to Jicheng. Murong Sheng's father-in-law Lan Han then took control of Longcheng and offered to welcome Murong Bao back. Murong Sheng, not trusting his father-in-law, advised his father to secretly advance south to try to join forces with his granduncle Murong De, who had been still defending Yecheng, not realizing that by that point Murong De had abandoned Yecheng and regrouped at Huatai (滑台, in modern Anyang, Henan) and declared his own independent state of Southern Yan. As Murong Bao and Murong Sheng arrived in vicinity of Huatai, however, they realized this and fled back north again. On the way, Murong Sheng tried to garner support from the people now under Northern Wei rule to coalesce around Murong Bao to start a new resistance, but Murong Bao, now believing in Lan Han's loyalty, was resolved to return to Longcheng despite Murong Sheng's misgivings. Murong Sheng, after being unable to change his father's mind, left his father and hid himself.