Yuan Shao had maintained good relations with…

Yuan Shao had maintained good relations with the Wuhuan beyond the imperial borders during his campaign against rival warlord Gongsun Zan, their common enemy, in the 190s.

Yuan Shao had given the chieftains of his Wuhuan allies seals and insignia as chanyu after the final destruction of Gongsun Zan in the Battle of Yijing in 199, and has reinforced the alliance by marrying the daughters of his subordinates to the Wuhuan leaders, pretending as though the daughters were his own.

The Wuhuan war leader Tadun was especially powerful and was thus very well-treated by Yuan Shao.

The Wuhuan have continued to support the Yuan clan after Yuan Shao's defeat at the Battle of Guandu against Cao Cao.

Subsequently, Yuan Shao's oldest and youngest son, Yuan Tan and Yuan Shang respectively, fought among themselves in a succession feud, which Cao Cao had exploited for himself.

Soon Yuan Tan was killed in a battle against Cao Cao and Yuan Shang had to flee to his second brother, Yuan Xi, in You Province.

The Yuan brothers in You Province had then been the targets of a mutiny against them, and had fled further north to seek protection from the Wuhuan, who have been united under the military leadership of Tadun, whose apparent strength prompts rumurs that he is seeking to emulate Modu Chanyu of the Xiongnu and Tanshihuai of the Xianbei in creating a hegemony over the northern nomadic tribes.

With the arrival of the Yuan brothers, accompanied by a considerable number of their followers, Tadun has gained command of a combined Wuhuan and Chinese force that is said to have numbered up to three hundred thousand.

In the name of helping Yuan Shang regain his territories, the Wuhuan make several raids across the imperial border, and are said to have kidnapped over one hundred thousand Chinese families.

Posed with such danger in the north, Cao Cao contemplates the elimination of the Wuhuan threat.