Between the 3rd century and the 5th century, Murong Hsien-pias established several regimes successively which were Former Yan, Later Yan, Northern Yan, Western Yan and Southern Yan. The Several Yans of Murong located in the area of Northeast with Koguryo. They all wanted to change over to new ways and had many conflicts. At the end of Later Yan, the dominance of Murong was extravagant and dissipated, the domination made the masses have no means to live. In 407 A.D., Feng Ba who was the officer of Later Yan made the opportunity which was Murong Xi attended the funeral procession for Litter Funv would kill Murong Xi and then crown Murong Yun (primitive name is Gao Yun, Koguryo) as the king of Yan, who was the foster son of Murong Bao. It was called Northern Yan by historians. From the perspective of each benefit, they maintained the friendly relationship between Koguryo and Northern Yan. When Northern Wei was fight with Northern Yan, Koguryo protected and rescued Feng Hong who was the king of Northern Yan. Koguryo also arrange Feng Hong for the area of Liao Dong and maintained the status of the king of Northern Yan. Afterwards, Feng Hong insulted the king of Koguryo, he would go to Southern Dynasty and then he was killed by the king of Changshou Koguryo, in order to remit strained the relation between Koguryo and Northern Wei, then the relationship between Koguryo and Northern Wei were collapsed. All the people of Northern Yan belonged to Koguryo, the national power of Koguryo was replenished much more. With the extinction of Northern Yan, the king of Changshou Koguryo carried out the flexible foreign policies to Southern and Northern Dynasties, it made Koguryo sustain the status of powerful state in the northern eastern areas.