In 333, Yuwen Qidegui, the head chief of the clan, was driven out (or killed) by Yidougui, who then made himself the new chieftain.
Huang accepted it, but before leaving, he built two forts named Anjin (安晉) and Yuyin (榆陰) between his and Yidougui's territory.
The envoys stayed overnight outside the city, where they were ambushed by Murong Huang's general Zhang Ying (張英).
Ten of Yidougui's men were killed while Duan Liao's envoys were all captured and brought to Murong Huang.
In 338, Murong Huang, now Prince of his established state, Former Yan, and Shi Hu of Later Zhao agreed to hold a joint campaign to subjugate the Duan tribe.
Knowing this, Han pretended to go mad, which he did so convincingly enough to cause the Yuwen to hate him but also underestimate him and not monitor his activities.
Moqian Hun thought that Huang was afraid to face him, so he did not prepare any defences and instead spent his time drinking and hunting.
As tribute to Zhao, Yidougui handed Duan Lan over to Shi Hu along with 10,000 fine horses.
The Yan forces pressed on and chased after the fleeing Yuwen troops into their capital in Zimengchuan (紫蒙川, northwest of present-day Chaoyang, Liaoning).
[9] Yidougui managed to flee the city, running away to the northern desert and later moving to Goguryeo where he would remain for the rest of his life.
He served as Chief Commandant of Escorting Cavalry and was bestowed the title of Duke of Xuantu Commandery.