We will talk about this question in two parts: "After Cao Cao led Yanzhou" and "After Cao Cao occupied Yuzhou"
In these two periods, the territory owned by Cao Cao can be called the "land of four battles", but the situation and the enemies he faced were different.
1. The land of right and wrong: Yanzhou
How Cao Cao entered Yanzhou, I will not go into details, it is not within the scope of the problem. Everyone only needs to know that Cao Cao is the number one horse boy under Yuan Shao at this time, how can he do it without a territory?
After Cao Cao parachuted into Yanzhou in 192 with the help of Yuan Shao's power, although nominally the chief executive of this place, in order to become the ruler, there were two mountains between the two, the "family clan" and the "indigenous tyrant", which Cao Cao had to conquer. This is internal.
In terms of external troubles, after Dong Zhuo fled west, the situation in the Central Plains was basically fixed as two Yuan fighting for the world. On this basis, the major princes began to join forces:
Yuan Shu, Gongsun Zhan, and Tao Qian worked together to deal with Yuan Shao.
Yuan Shao was in a group with Cao Cao and Liu Biao, the latter two were responsible for containment, and Yuan Shao was concentrating on dealing with Gongsun Zhan.
In April 193, Yuan Shu eyed Cao Cao's unstable foothold in Yanzhou, personally led his army to attack Chen Liu Commandery, occupied more than a dozen county towns, and also brought in the Black Mountain Army and the Southern Xiongnu Yufuluo, who had previously been defeated by Cao Cao. At the same time, Tao Qian also raised troops from the east to attack Taishan County. Cao Cao faced a severe test for a while. Fortunately, Yuan Shao sent troops to the rescue, and Liu Biao harassed Yuan Shu's rear, and finally helped Cao Cao break Yuan Shu at Kuangting, and drove Yuan Shu directly out of the Yanzhou border and back to Yuzhou, and incidentally took Liang Guo County in Yuzhou, winning a big victory.
After driving away Yuan Shu, Tao Qian immediately withdrew when he saw that the situation was wrong, but Cao's army was already in sight.
As we said earlier, Cao Cao parachuted to Yanzhou territory by relying on Yuan Shao's power, and did not gain the support of Yanzhou people, which was very fatal. And if you want to gain the support of these warriors, you must either be gentle or kill them directly. But Huairou is impossible, Cao Cao does not have that strength at the moment, a light pole commander, no common interests, at most can only obtain the support of some local small marshals and cold warriors. And Yuan Shao was also happy to see the contradictions between Cao Cao and Yanzhou Shiren inspired, so that he could reap the benefits of fishermen in the future.
Therefore, Cao Cao knew that Yanzhou could never be used as a base camp, so he set his sights on the territory of Xuzhou.
Therefore, this is a good explanation of why Cao Cao wanted to slaughter the city in Xuzhou.
During Cao Cao's second march in the Xuzhou Crusade, he could have taken Tao Qian's head directly, why did he go around most of Xuzhou and slaughter it all before he was satisfied?
It is because of what we analyzed above that Cao Cao wanted to reshuffle the political situation by slaughtering the Xuzhou clan and prepare himself for his future entry into Xuzhou. The real strong will not be swayed by feelings, and avenging their father is just an excuse. You see, when Cao Cao knew that Chen Gong and Lü Bu had kicked the old nest in Yanzhou, his first reaction was not to hurry back, but to think that he would either directly take the whole of Xuzhou and let Lü Bu and Chen Gong take over the mess in Yanzhou themselves.
Unfortunately, Yuan Shao's mind was also very thorough, he had long expected that Cao Cao would have this step, first sent Zhu Ling to monitor, and then quietly sent people to quickly win over a group of Xuzhou people, including Kong Rong and Chen Deng, when Tao Qian's camp almost collapsed, and then sent Yuan Tan to throw an olive branch to Liu Bei (because Liu Bei could not throw himself at Cao Cao) to make Liu Bei ready to take over as Xuzhou Mu. Cao Cao, at the moment when he was about to take Xuzhou, was severely slapped in the face by Yuan Shao's political forces.
Helpless, really helpless, Xuzhou is already Yuan Shao's territory. Facing Xuzhou, Cao Cao originally thought of breaking the jar and breaking it, and when he planned to tear his face with Yuan Shao, it was Xun Yu who persuaded him in time and spent a lot of effort to pull Cao Cao back from the cliffside. Cao Cao had to obediently turn around and beat Lü Bu.
Later it turned out that Cao Cao was actually not afraid of Lü Bu at all, he just didn't want to go back to take over this hot potato. In Yanzhou, the power that could be absorbed, Cao Cao had already absorbed it, and all that remained were chess pieces arranged by Yuan Shao to restrain Cao Cao. It's not good to have the ability to be empty, but to be restrained everywhere.
Fortunately, this situation was suddenly opened, and Cao Cao saw the light of the future.
Second, the place of origin: Yuzhou
After Liu Bei took over Xuzhou, he fell to Yuan Shao without suspense, the hatred in Yuan Shu's heart, what is this Liu Bei that suddenly appeared? So he sent troops to attack Xuzhou.
Cao Cao, on the other hand, seized most of Yuzhou's territory when Yuan Shu and Liu Bei were at odds in Xuzhou, and from then on ruled both Yan and Yuzhou.
Yuan Shu first died in battle because Sun Jian died, and he lacked the power to compete with Cao Cao for Yanzhou, and now he was still taken advantage of, and Xuzhou did not get it back, and he also cheapened Lü Bu, the little rabbit cub. Depressed, Yuan Shu had to move his development direction to Yangzhou, Huainan.
Cao Cao, on the other hand, heeded Xun Yu's advice and transferred his base camp from Yanzhou East County to Yingchuan County in Yuzhou. Can you imagine Xun Yu patting his chest in front of Cao Cao and saying: "I, Xun Lingjun, am in Yingchuan, and I haven't found a second one who dares to fight me. "This is probably the best time for their relationship. Thus, Cao Cao welcomed Emperor Xian of Han in Xu County, Yingchuan. In Yingchuan, Cao Cao had no internal worries at all, because Xun Yu was there.
At the same time, against Yanzhou, Cao Cao left Yanzhou Hanshi Cheng Yu and asked him to play a game with Yuan Shao's forces in Yanzhou. For Xuzhou, he adopted a gesture of co-optation, because the first enemy that Cao Cao had to face at this time was:
Yuan Shu of Huainan and Zhang Xiu, who was attached to Liu Biao.
Needless to say, as long as Cao Cao wanted to form a confrontation with Yuan Shao, Yuan Shu would definitely get rid of it first. As for Zhang Xiu, it was purely because the city of Wancheng where he was located was located in Yuzhou, and Cao Cao only wanted to sweep away the remaining forces in his territory, but who knew that he kicked the iron plate.
We will not tell much about the story of Cao Cao's fight against Zhang Xiu, but in short, Cao Cao eventually acquiesced to Zhang Xiu's independence, listened to Xun Fu's opinion, and slowed down the army, shifting his focus to Lü Bu, who replaced Liu Bei in Xuzhou.
Oh, by the way, explain Yuan Shu. After Yuan Shu became emperor, he was attacked by Sun Ce, Lü Bu, and Cao Cao, and Sun Ce rebelled against Wu Jing, Sun Ban and other clansmen; Lü Bu plundered Yuan Shu's Huaibei as if he were in no man's land; Cao Cao beat Yuan Shu, who was trying to regain Yuzhou, once again to the fullest. Yuan Shu declared himself emperor, pushed himself to the abyss of defeat, and killed himself.
After Cao Cao defeated Lü Bu, he originally wanted to accept Lü Bu's surrender. As a result, Liu Bei expressed his position on the side, in fact, secretly conveying Yuan Shao's meaning, so Cao Cao still executed Lü Bu. He didn't want to tear his face with Yuan Shao for the time being, even if their relationship was no longer a honeymoon period after Xu County welcomed the Son of Heaven.
Cao Cao eventually handed Xuzhou over to the local tyrant Zang Ba, which was a satisfactory result for both Cao and Yuan, because it allowed Xuzhou to remain neutral for a while, and even Zang Ba himself was actually more inclined to Cao Cao. Moreover, Cao Cao also divided three more counties into three counties of Langya, Donghai and Beihai in Qingzhou, and installed his own manpower, which can be regarded as gaining basic control. Coupled with the later blitz attack on Xuzhou, Cao Cao took Xuzhou before the decisive battle with Yuan Shao, of course, this is a later story.
After the problem on Xuzhou's side was resolved, Cao Cao set his sights on Hanoi County south of the Yellow River, and after capturing Hanoi County, he first betrayed his alliance with Yuan Shao and attacked Jizhou, intending to take advantage of Yuan Shao's annexation of Gongsun Zan before he could annex Gongsun Zhan.
As a result, Yuan Shaocha eliminated Gongsun Zan at this time, so frightened that Cao Cao immediately led his army back to the south of the Yellow River and concentrated his forces on Guandu.
summary
At this point, Cao Cao was ready to start the battle of Guandu with Yuan Shao, and at this time, Cao Cao was already under the protection of Yuan Shao, and the blue was better than the blue, and the apprentice was going to defeat the master in turn. Cao Cao was able to start in the land of four battles, in addition to relying on Yuan Shao's help, there was also Xun Yu's help, coupled with Cao Cao's excellent military ability, plus Yuan Shu did a good job. These factors together built the road to Cao Cao's rise.
However, I think that Cao Cao's eventual rise was due to Yuan Shao's death shortly after the Battle of Guandu, leaving behind three stupid sons, and if Yuan Shao did not die, there would definitely be strength to make a comeback. There is a chance to talk about this later.