Guo Jia
In chapter 33 of the novel, Guo Jia was accompanying Cao Cao on his campaign against the Yuan brothers (Yuan Shang and Yuan Xi) and the Wuhuan when he fell sick because he could not adjust to the climate. He advised Cao Cao to leave the heavy baggage behind and launch a swift attack on the enemy with a light force, which resulted in Cao's victory later at the Battle of White Wolf Mountain. Guo Jia remained in Yizhou () to recover and did not follow Cao Cao to the frontline. When Cao Cao returned to Yizhou later, he was deeply grieved to hear that Guo Jia had already died several days ago. Before his death, Guo Jia wrote Cao Cao a note, whose contents were not revealed until later in the chapter. When Cao Cao received news that Yuan Shang and Yuan Xi had fled to Liaodong to join the warlord Gongsun Kang, his subordinates urged him to either attack Liaodong or return to Xu (許; present-day Xuchang, Henan), but Cao told them to wait until they had received the Yuan brothers' heads. Just then, Cao Cao heard that Gongsun Kang had captured and killed the Yuan brothers and sent their heads to him, and his followers were very surprised. Cao Cao then revealed Guo Jia's note, which stated: "I heard that Yuan Xi and Yuan Shang had fled to Liaodong. You should not mobilise the army. Gongsun Kang had long feared that the Yuans would conquer his territory so he would definitely feel suspicious when the Yuan brothers join him. If you attack them, they will unite to resist you and you cannot overcome them quickly; if you do not move, Gongsun Kang and the Yuans will fight each other, and this is definite."