Guo Jia is a brilliant strategist, he is famous for his wisdom and strategy, and is known as a "ghost talent". He has two extraordinary strengths. One is his keen ability to recognize people, and the other is his accurate ability to predict, often able to ** the development of things, and never miscalculated. 
Knowing people is Guo Jia's most praised talent. He had served Yuan Shao, however, he had a unique vision and saw early on that Yuan Shao was not the master. So, he decisively left Yuan Shao and chose to defect to Cao Cao, which is enough to prove his accuracy in knowing people. When he was under Yuan Shao, Guo Jia had already noticed many of Yuan Shao's shortcomings. He knew very well that although Yuan Shao was expected by the world, his strength was insufficient and his actions were unreliable. At that time, everyone thought that Yuan Shao would dominate the world, but Guo Jia held his own opinion and chose to retire temporarily. He waited for the right time at home and enjoyed a quiet life for five or six years. Later, Xun Yu recommended Guo Jia to Cao Cao. At that time, Cao Cao's power was still small, and he was powerless compared to Yuan Shao. However, after a brief conversation with Cao Cao, Guo Jia decided that Cao Cao was by no means an extraordinary person, so he did not hesitate to choose to follow Cao Cao and give him advice. 
In addition to knowing people, Guo Jia also has the ability to have the future. His ability is quite similar to Zhuge Liang's talent for divination, but his ** comes from the depths of his heart. For example, in the Battle of Guandu, Cao Cao was suspicious of his resolve with Yuan Shao. At this time, Guo Jia predicted that Sun Ce would take action, but he concluded that Sun Ce would encounter an accident. Sure enough, Sun Ce was plotted soon after. This further deepened Cao Cao's trust in Guo Jia. In addition, when Liu Bei took refuge in Cao Cao, Guo Jia once reminded Cao Cao to beware of Liu Bei. He believed that Liu Bei would become Cao Cao's fierce rival. However, in order to show his demeanor as a corporal of courtesy, Cao Cao did not adopt Guo Jia's advice, which also laid the groundwork for his later predicament. So, how did Guo Jia see Sima Yi's ambition?
Sima Yi acted meticulously and was quite deep in the city, but he was still seen through by Guo Jia. It turned out that although Sima Yi was born in a famous family, he despised Cao Cao in his heart. He initially refused to serve as an official under the pretext of illness, until he was forcibly recruited by Cao Cao and reluctantly served the Cao family. And his flawless performance and flawless appearance made Guo Jia suspicious. Guo Jia believes that this kind of perfection is actually the biggest disguise and the city. He knows that ambition is often hidden behind perfection. Therefore, he left his last words before he died: "Sima Yi has far-reaching tactics, and he can't kill him if he can't use it." He believed that those who posed a threat to Cao Wei's regime must be vigilant, and would rather kill them by mistake than let one go. Unfortunately, Cao Cao and Cao Pi did not take his advice.
It can be seen that Guo Jia's ability to recognize people and deduce things is indeed amazing. He has insight into the world and understands human feelings, which can be said to be insightful and knowledgeable, and human feelings are articles. If Cao Cao and Cao Pi had taken his advice, perhaps Cao Wei would have been able to continue for hundreds of years. However, history cannot be changed, leaving only regrets and regrets.