Guo Si, also known as Guo Duo, was a Chinese military general, politician, and warlord serving under the warlord Dong Zhuo during the late Eastern Han dynasty of China. He assisted Dong Zhuo in his many campaigns and served as a subordinate of Dong Zhuo's son-in-law, Niu Fu, after Dong Zhuo relocated the imperial capital to Chang'an. He later became one of the de facto regents of Emperor Xian, wherein they occupied the capital and held the emperor and imperial officials hostage. However, his downfall came when he quarrelled with his co-regent, Li Jue. He and Li Jue were ultimately defeated by Yang Feng and Dong Cheng, who assisted the emperor to flee the capital. Guo Si was eventually betrayed and murdered by one of his subordinates.

Jia Xu, courtesy name Wenhe, was an official of the state of Cao Wei during the early Three Kingdoms period of China. He started his career in the late Eastern Han dynasty as a minor official. In 189, when the warlord Dong Zhuo took control of the Han central government, he assigned Jia Xu to the unit led by Niu Fu, his son-in-law. In May 192, after Dong Zhuo was assassinated by Lü Bu, Jia Xu advised Li Jue, Guo Si and Dong Zhuo's loyalists to fight back and seize control of the imperial capital, Chang'an, from a new central government headed by Lü Bu and Wang Yun. After Li Jue and the others defeated Lü Bu and occupied Chang'an, Jia Xu served under the central government led by them. During this time, he ensured the safety of the figurehead Han emperor, Emperor Xian, who was being held hostage by Li Jue. He also attempted to prevent internal conflict between Li Jue and Guo Si, but with limited success. After Emperor Xian escaped from Chang'an, Jia Xu left Li Jue and briefly joined the general Duan Wei before becoming a strategist of the warlord Zhang Xiu. While serving under Zhang Xiu, he advised his lord on how to counter invasions by the warlord Cao Cao, who had received Emperor Xian in 196 and taken control of the central government. In 200, during the Battle of Guandu between Cao Cao and his rival Yuan Shao, Jia Xu urged Zhang Xiu to reject Yuan Shao's offer to form an alliance and instead surrender to Cao Cao. Zhang Xiu heeded his advice. Jia Xu then became one of Cao Cao's strategists.