Five years after Hun entered Jian'an, he worked for Zhang He's younger brother Zhang Jin, also known as Zidu. He knew that Yuan Shao would be defeated, so he refused to be the vanguard of his death on a white horse. Using his brother's cover, he secretly contacted Xu You to find out what was going on. When he was in Guandu, he led his own soldiers to defect to help Cao Cao defeat Chunyu Qiong in exchange for capital. He collected the Yellow Turban soldiers from Qingzhou and the exiled scholars in Yingchuan, and welcomed Emperor Xian's failed attempt to move westward, so he separatized the Hanzhong-Brazil Corridor and accepted Zen.
Not bad, you can take a look