In the early stage, it was Guo Jia, and in the later stage, it was Sima Yi. Guo Jia was born in Yingchuan, which is today's Dengfeng area in Henan. Sixty-seven out of ten counselors come from this place. Guo Jia showed extraordinary wisdom in his youth. He liked to talk with the elders and often had unique insights, which often made the elders feel ashamed. Once, a sorcerer from out of town was amazed when he saw little Guo Jia, calling the boy the reincarnation of Grand Duke Jiang Ziya. From then on, Guo Jia had a nickname - "Little Grand Duke". Time passed, and Guo Jia, who was well-read in poetry and books, grew up in an instant. He is thin and handsome, and has a pair of clear and deep eyes. This "little grandpa" is confident and aloof. He likes to be unrestrained. He is very picky about making friends and only associates with people with lofty ideals. But he is very sincere and enthusiastic towards his friends and likes to drink and talk all night long. When Guo Jia was 21 years old, he defected to Yuan Shao's tent at the instigation of his friend Tian Feng and others. Yuan Shao was called "the hero of the world" at that time. He respected Guo Jia and others very much and treated them with courtesy. But after dozens of days, Guo Jia realized that Yuan Shao did not know how to employ people and was not a man who could achieve great things. Therefore, Guo Jia left Yuan resolutely. Guo Jia left Yuan Shao when he was at his most prosperous. This not only required great courage, but also extraordinary vision. In this way, Guo Jia has been unemployed for 6 years. In 196 AD, one of Cao Cao's most valued advisors, Xi Zhicai, passed away. Feeling sad, Cao Cao wrote to Xun Yu and asked him to recommend a counselor who could succeed Xi Zhicai. Therefore, Xun Yu recommended his friend Guo Jia to Cao Cao. Cao Cao was overjoyed. He welcomed Guo Jia ten miles away and took him into his camp to discuss world affairs. The importance of this meeting was by no means less than that of the later "Longzhong Duo". Guo Jia was younger than Cao Cao, but he seemed to know Cao Cao's great national ambitions very well. When Cao Cao asked Guo Jia about the situation in the world, Guo Jia made it clear. The key is to take advantage of Cao Cao's opportunity to attack Gongsun Zan. This will not only expand Cao's army's strength, but also prevent Lu Bu from threatening Cao's army from the flank during the decisive battle between Cao and Yuan. Cao Cao also asked Guo Jia about the most critical qualities as a counselor. What is it? Guo Jia said that war is like playing chess. No war is planned in advance. Being familiar with the art of war is just an introduction. The strength of a military advisor lies in adapting to situations. Guo Jia's clear and thorough analysis allowed Cao Cao to see the bright future. In the future. After hearing this, Cao Cao sighed, "This is the person who can accomplish great things alone." ’ After Guo Jia left the camp, he was overjoyed and said, “He is my true lord.” From then on, Guo Jia became Cao Cao’s military staff officer, offering military sacrificial wine to Cao Cao for his campaigns in all directions and serving faithfully. Ingenious calculations and wonderful achievements were made repeatedly. At that time, the princes from all walks of life were separatist and had no ambition to swallow up the whole world. In this case, Guo Jia's accurate judgment of the psychological state of each opponent often became the key to Cao Cao's victory. In 197, when Cao Cao was worried that he did not have the ability to compete with Yuan Shao, Guo Jia put forward the famous saying of "ten wins and ten losses." He cited ten reasons in a row to prove that "the public has ten victories and Shao has ten defeats." Guo Jia's analysis was very convincing. It not only boosted the fighting spirit of Cao Cao's soldiers, but also helped Cao Cao formulate long-term and short-term combat goals. At the same time, Guo Jia also formally established his core position in Cao Cao's military intelligence group. In September 198, Cao Cao adopted Guo Jia's plan and sent troops to attack Lu Bu who was in Xuzhou. Cao Jun first defeated Pengcheng, then Lu Bu, and finally besieged Xiapi. Lu Bu couldn't hold on. The battle lasted for more than half a year. When Cao Cao saw that his soldiers were tired, he was ready to give up. At this time, Guo Jia saw a chance to win. He used Xiang Yu as an example to admonish Cao Cao, and put forward the view that "a brave but unintelligent person will soon be defeated if his energy fails and his strength is exhausted." He advised Cao Cao to attack urgently. Cao Cao followed Guo Jia's plan, attacking the city while breaching the embankment to cover Xia Xing. As expected, he captured Xia Xing in the same month and captured Lu Bu. Under normal circumstances, Cao Cao obeyed Guo Jia's advice. But there was only one time when he did not listen to Guo Jia's advice and made an irreparable mistake, that is, letting Liu Bei go in 199. After Liu Bei defected to Cao Cao, everyone initially suggested killing him to avoid future troubles. Only Guo Jia agreed with Cao Cao and believed that Liu Bei could not be killed. Guo Jia's original intention was to let Cao Cao put Liu Bei under house arrest. Because if Liu Bei is killed, it will definitely have a bad impact on Cao Cao and cut off the path of talents. Although they cannot be killed, they must not be released. But Cao Cao had only a partial understanding of Guo Jia's meaning, which led to a big mistake.

After Cao Liu drank and discussed heroes, Liu Bei was worried about Cao Cao's suspicion, so he wanted to wait for an opportunity to escape from Cao Cao's control. Liu Bei pretended to take advantage of Yuan Shu's defeat and took the initiative to request Cao Cao to intercept. At this time, Guo Jia happened to be away and Cao Cao agreed to Liu Bei's request. When Guo Jia came back and learned of the incident, he immediately said, "It is necessary to be prepared." Cao Cao also regretted it at the time and immediately sent people to chase him, but it was too late. Sure enough, later Liu Bei took control of Xuzhou and began to fight against Cao Cao. This place was the largest talent pool during the Three Kingdoms period. Among Cao Cao's many advisers who advised various heroes at that time, only Guo Jia knew Cao Cao best, and the two had a close relationship, like friends. According to reports, the two traveled in the same car and sat at the same table, which shows their closeness. In Cao Cao's camp, who was strict in running the army, Guo Jia had many unconventional behaviors, but in the eyes of Cao Cao, who favored him, he was an extraordinary person and should not be restrained by common sense." Cao Cao had a disciplinary inspection official named Chen Qun had been punished because of his lack of discipline. However, while Cao Cao praised Chen Qun for his report, he ignored Guo Jia. Not only that, Cao Cao also secretly maintained his old ways for Guo Jiayi. During his long campaign, Cao Cao always took Guo Jia with him so that he could discuss things at any time and act according to the situation. Some historians said that Guo Jia was lucky. Only a man with great talent and strategy like Cao Cao could. Cao Cao dared to use people like Guo Jia who despised etiquette and regarded him as a "confidant". Whenever there was a major military event, Guo Jia's strategy never failed. Cao Cao placed unlimited hopes on the young Guo Jia and planned to pacify it. After the war, he entrusted Guo Jia with the important affairs of governing the country after his death. Guo Jia's important position in Cao Cao's group can even be divided into two parts according to Guo Jia's death. Unified the North: In the battles in which Cao Cao defeated Lu Bu, Yuan Shao and other troops, Guo Jia played the most important role. After Guo Jia's death, Cao Cao achieved some successes in the northwest war with Ma Teng, Han Sui and other grassroots warlords. , basically in a stagnant situation. After the Battle of Chibi in 208, there was a helpless ending of three points in the world. Cao Cao himself understood this deeply, otherwise he would not have issued a warning on the retreat after the defeat of Chibi. Such a lone ape lamented like blood: "Guo Fengxiao (Guo Jia) is here, so I don't want to be alone here. "It's a pity to show filial piety! It's painful to show filial piety! It's sad to show filial piety!