In the early period of the Three Kingdoms, there were three camps of confrontation, the first was from the first year of Chuping (190) to the second year of Chuping (191) (Note 1) because Dong Zhuo abolished the establishment of the king and led to a crusade against the princes, and the two camps of Dong Zhuo and anti-Dong were formed. As a result, the anti-Dong alliance was dissolved, and the internal division began.

The second is the confrontation period between the two Yuans, Yuan Shao's approach led to a complete rupture of the Yuan brothers, so with these two brothers as the core, the confrontation between Yuan Shu, Tao Qian, Gongsun Chan and Yuan Shao, Cao Cao, and Liu Biao was formed respectively, and the time lasted from the second year of Chuping (191) to the fourth year of Jian'an (199) Yuan Shu and Gongsun Zan were destroyed.

In the development and growth of the Yuan Shao Alliance, the contradictions between Yuan Shao and Cao Cao are also intensifying, in the fourth year of Jian'an (199) Yuan Shao has occupied the four major states of Youzhou in the north, Jizhou, Bingzhou and Qingzhou, with strong strength, becoming the strongest princes at that time, Cao Cao coerced the Son of Heaven and ordered the princes, and also occupied the land of several states in the Central Plains, they were opposed to each other, and a war was inevitable.

The confrontation between Yuan and Cao Cao was divided into two periods by the Battle of Guandu.

[Before the official crossing: Yuan Qiang and Cao Weak]

This stage is mainly from the fourth year of Jian'an (199) to the fifth year of Jian'an (200), Cao Cao won the decisive battle of Guandu and won the victory against Yuan Shao, achieving a reversal of strength and weakness.

In the fourth year of Jian'an, Cao Cao's territory was actually no less than Yuan Shao's, and his talents still had obvious advantages over Yuan Shao, but because Cao Cao's territory had been conquest for many years, the consumption was far greater than Yuan Shao's, so the strength was indeed weaker than Yuan Shao, but the two were still a level of princes.

Another unfavorable situation for Cao Cao is that Cao Cao's territory is located in the Central Plains and has basically contact with other princes, while Yuan Shao occupies the north and the rear is relatively stable, so Cao Cao cannot concentrate his forces against Yuan Shao, on the contrary, Yuan Shao has deployed troops to fight against Cao Cao.

At the same time, Liu Bei rebelled and seized Xuzhou, the princes of Guanzhong were also ready to move, Zhang Xiu and Cao Cao in the south fought many times, Liu Biao was also a loyal ally of Yuan Shao, Sun Ce's relationship with the imperial court gradually drifted apart, and he had the intention of taking the opportunity to go north, Cao Cao's internal turmoil was also in turmoil, and Dong Cheng and others were also conspiring to get rid of Cao Cao by relying on the emperor's order.

On the whole, in the early days of Yuan Cao's confrontation, the situation was very unfavorable for Cao Cao. But Cao Cao did not give up in this predicament, he and his advisers and generals worked together, coupled with God's care, to bring the situation back little by little.

In the face of Liu Bei's rebellion, Cao Cao, in order to make up for his mistakes, boldly attacked, crusaded against Liu Bei under Yuan Shao's nose, caught him off guard, and successfully drove Liu Bei out of Xuzhou. And the princes of Guanzhong also stabilized under the appeasement of Zhong Xuan, who was recommended by Xun Yu, and relieved Cao Cao's worries on the western front.

In the center, Cao Cao and others discovered Dong Cheng's conspiracy in time, and dealt with it decisively to minimize the losses and impacts, and Xun Yu and Cao Cao also gained the upper hand in the dispute with the appeasement faction, temporarily suppressing the opposition and stabilizing the interior.

In the south, Zhang Xiu's submission was an unexpected joy, and Liu Biao's inaction further eased Cao Cao's external pressure, only the Jiangdong overlord Sun Ce was the most prosperous, but unfortunately he was not good at seeking his own life, and was assassinated in Guo Jia's expectation, and did not actually threaten Cao Cao.

So by the time Yuan Shao went south, Cao Cao could already put down some of his burdens and fight.

The Battle of Guandu was one of the two most important battles of the Three Kingdoms era, and its status and influence in history were on par with the later Battle of Chibi.

After Cao Cao won the Battle of Guandu, he completely reversed his unfavorable situation and replaced Yuan Shao as the most powerful prince at that time.

[After the official crossing: Cao Cao destroys Yuan]

Although Yuan Shao was strong in history, he had already gone through many major battles such as Zang Hong and Gongsun Zan before he crusaded against Cao Cao, and the soldiers and the people were already exhausted, and the internal contradictions were also unprecedentedly intensified, and the so-called good situation was only better than Cao Cao's, so the defeat of Guandu was a pain that the Yuan group could not bear.

Yuan Shao reluctantly quelled the internal rebellion on the one hand, and on the other hand, he had to face Cao Cao's continuous provocations on the front line of the Yellow River, physically and mentally exhausted, and finally died in the spring of the fifth year of Jian'an (202).

Although Yuan Shao died, he left a big problem for the old Yuan family, that is, Yuan Shao did not decide his heir, and this matter left endless troubles for the Yuan family.

At that time, the main ones who could inherit Yuan Shao's position were the eldest son Yuan Tan and the third son Yuan Shang, and the two of them had a faction to support, but Yuan Shang's faction took advantage of Yuan Tan's absence to Yecheng to forge Yuan Shao's suicide note to make Yuan Shang ascend to the throne, so Yuan Tan was very unconvinced and called himself a general of the chariot cavalry.

Cao Cao saw that there was an opportunity in the north, so he led the army to the north, Yuan Tan, who was in Liyang at the time, could not resist Cao Cao, and asked Yuan Shang for reinforcements, but Yuan Shang was afraid that the army he sent would be annexed by Yuan Tan, so he personally led troops to support Yuan Tan, but the two brothers were not in harmony with each other, and could not twist into a rope, and in the face of Cao Cao's pressure, they were defeated and retreated all the way back to Yecheng, and Cao Cao easily hit Yuan's base camp. Cao Cao then temporarily retreated at Guo Jia's suggestion.

After Cao Cao withdrew, Yuan Tan was lured by Guo Tu, Xin Ping and others to completely break with Yuan Shang, and the two sides fought outside the Yecheng Gate, Yuan Tan was defeated by the stronger Yuan Shang, and Yuan Tan was forced to retreat to Nanpi, and only gained a firm foothold with the help of Wang Xuan and others.

After that, Yuan Shang did not let Yuan Tan go, he took the initiative to lead the army to attack, defeated Yuan Tan in Nanpi, conquered the city, Yuan Tan retreated to the plains, chose to follow Guo Tu's advice and pretended to be affiliated with Cao Cao, induced him to crusade against Yuan Shang and sent Xin Bi as an envoy to meet Cao Cao.

Cao Cao, under the persuasion of Xin Bi and Xun You and others, gave up going south, and instead sent troops north, attacked Yecheng twice, and finally conquered Yuan's lair, defeated Yuan Shang, and after seeing Yuan Shang's defeat, Yuan Tan betrayed the alliance and annexed Yuan Shang's subordinates and territory, and Cao Cao sent troops to attack Yuan Tan and eliminate it.

Later, Yuan Shang took refuge in Youzhou's second brother Yuan Xi, and the two were forced to go north because of the betrayal of Yuan Xi's generals Jiao Touch and Zhang Nan, and took refuge in Wuheng people, Jizhou, Qingzhou, and Youzhou all fell into the hands of Cao Cao, and the state assassin Shi Gao Gan surrendered and rebelled, and was finally defeated by Cao Cao's crusade, and Gao Gan went south to take refuge in Liu Biao and was captured.

After the four northern states fell into the hands of Cao Cao, he defeated Wuheng in the Northern Expedition, and the Yuan brothers took refuge in Gongsun Kang of Liaodong and were captured and killed by him, and the Northern Yuan clan withdrew from the historical stage of the Three Kingdoms, and the confrontation between Cao and Yuan also ended completely.

Note 1: Or by 192 Dong Zhuo was killed.