Murong Hui
As of 397, Gao Yun was a mid-level official in the administration of Murong Bao (Emperor Huimin), when Murong Bao, under military pressure by Northern Wei, abandoned the capital Zhongshan (中山, in modern Baoding, Hebei) and sought to take refuge at the old Former Yan capital Longcheng (龍城, also in Jinzhou). On the way, his son Murong Hui, resentful that his younger brother Murong Ce (慕容策) was made crown prince over him, rebelled, and while Murong Bao was able to reach Longcheng, Murong Hui put Longcheng under siege. During one night, Gao Yun led about 100 soldiers and made a surprise attack on Murong Hui's camp, causing Murong Hui's army to collapse. Murong Hui fled to Zhongshan and was killed there. For Gao Yun's contributions, Murong Bao created him the Duke of Xiyang and adopted him as his own son, and so his name was changed to Murong Yun. It was around this time that he befriended another general, Feng Ba, as Murong Yun was not looked upon favorably by others because he was a man of few words, but Feng Ba saw that he had wisdom and tolerance.