180s–205), born Chu Yan, also known as Zhang Feiyan, was the leader of the Heishan bandits during the late Eastern Han dynasty of China.
[9] With Zhang Yan's energy and military reputation, his confederation steadily grew in strength, until they were said to be one million strong though historians suggest more in the tens of thousands.
[14] All the commanderies north of the Yellow River were exposed to their attacks and while Lu Zhi was able to drive Zhang Yan forces away from Henei, the Han could not suppress the rebellion.
[17][6][18] By the early 190s with the land in civil war, Zhang Yan had formed an alliance with the warlord Gongsun Zan against their common opponent, Yuan Shao.
Yuan Shao responded with force, allying with reinforcements from some of the Wuhuan and Xiuchuge tribes with the support of Lü Bu, marching 250 kilometers (over 150 miles) through the Taihang Mountains, destroying the Heishan bandit camps as he went.