Liu Biao
Cai Mao was known for being arrogant and proud. He served as a military officer under his brother-in-law Liu Biao, the Governor of Jing Province. In 190, when Liu Biao first started his tenure in Jing Province, Cai Mao, along with Kuai Liang and Kuai Yue, assisted him in quelling local rebellions and consolidating control over the province. Cai Mao subsequently served as the Administrator () of various commanderies in Jing Province, including Jiangxia (), Nan Commandery () and Zhangling (). In 192, after Liu Biao received the honorary appointment of General Who Guards the South () from the Han imperial court, he appointed Cai Mao as his military strategist.