Early 199 AD,Yuan Shao袁绍, who had defeated Gongsun Zhan公孙瓒, began to march on the north bank of the Yellow River, preparing to wait for the opportunity to cross the river to the south to fight against Cao Cao.
While Cao Cao also began to make comprehensive arrangements for the upcoming war.
He first sent Shi Huan史涣 and Cao Ren曹仁 to defeat Sui Gu眭固 and capture He'nei河内 commandery, which is to the north of Yellow River, then he sent Zang Ba 臧霸 to lead troops into Qingzhou青州 to hold Yuan Shao’s back ,from both east and west.
At the same time, Cao Cao ordered Yu Jin于禁 to garrison Yanjin延津, an important ferry port on the south bank of the Yellow River. And Liu Yan, the Commanderial governor of Dongjun东郡, to garrison Baima白马, and Cheng Yu程昱 to garrison Juancheng鄄城 to prevent Yuan’s army from crossing the river.
There were many advisers amoung Yuan Shao, but the most important was undoubtedly Ju Shou沮授 and Tian Feng田丰.
Ju Shou held an important position and had a high prestige in the army, played a role similar to Xun Yu荀彧 of Cao Cao, it was Ju Shou who first advised Yuan Shao to greet the emperor and plan the blueprint for Yuan Shao's great cause.
Tian Feng, was one of the main advisers at the tactical level, acting like Xun You荀攸 on Cao Cao's side. He planned a lot of Yuan Shao’s battles of beating Gongsun Zan.
In addition, Yuan Shao was surrounded by Xu You许攸, Pang Ji逄纪, Shen Pei审配, Guo Tu郭图 and others.
Before the war, there had been a fierce debate among these advisers, Ju Shou suggested that Yuan Shao should not rush a decisive battle, instead he should first fight a war of attrition, and use elite cavalry to constantly harass Cao Cao, so that Cao Cao could not have a chance to develop , and waiting until Cao Cao was wwea enough then launching a decisive battle, while Shen Pei and Guo Tu urged Yuan Shao to fight for a quick victory.
In the end, Yuan Shao decided to adopt the advice of the quick war faction and weaken the military power of Ju Shou.
There were many factions within the Yuan Shao’s clique, intrigue, and mutual fighting, which also buried the bane of its demise.
In Cao Cao's clique, Xun Yu, Guo Jia郭嘉 and other important strategists supported Cao Cao to fight, only Kong Rong孔融 spread pessimistic arguments, which also strengthened Cao Cao's determination to defeat the strong enemy.
In fact, Yuan Shao was not in a hurry to attack, but played diplomacy,
He first sent someone to contact Zhang Xiu张绣 in Wancheng宛城 and Liu Biao刘表 in Jingzhou荆州.
Liu Biao immediately agreed to cooperate, and then Yuan Shao also sent envoys to Yuzhou豫州, to plot with the comanderies of Yuzhou to jointly resist Cao Cao.
It must be known that Yuan Shao's hometown was Runan汝南 commandery in Yuzhou, and sure enough, under the contact of Yuan Shao and Liu Biao, all commanderies in Yuzhou responded, except for several counties, most of the commanderies and counties of Yuzhou all announced that they belonged to Yuan Shao and separated from Cao Cao.
At this time, Sun Ce孙策 of Yangzhou扬州 was also planning to attack Xuchang许昌 ,Ma Teng马腾 and Han Sui韩遂, who was in Guanzhong关中, was ostensibly promising not to help each other, but in fact they were ready to move.
Before the battle, Cao Cao was surrounded by enemies on all sides and was in a desperate situation.
However, just when Cao Cao was having a headache, he suddenly heard unbelievable good news, that is, Jia Xu贾诩,Zhang Xiu's most important strategist,actually rejected Yuan Shao's envoy in front of Zhang Xiu,and persuaded Zhang Xiu to surrender to Cao Cao,on the eve of the great war.
This sudden turn surprised Yuan Shao, and Cao Cao was ecstatic, if Zhang Xiu took advantage of the confrontation with Yuan Cao to sneak up on Cao Cao's rear, with Zhang Xiu's power and Jia Xu's strategy, Cao Cao was very likely to collapse.
Even if Zhang Xiu did not move, Cao Cao needed to take out a considerable part of his troops to defend him, and now Cao Cao not only eliminated this biggest threat behind him without spending a single soldier, but also increased his own strength. You must know that Zhang Xiu and his 5000 soldiers from Liangzhou凉州 made great achievements in the later Battle of Guandu官渡.
Previously, Cao Cao and Jia Xu had no personal relationship, and the reason why Jia Xu urged Zhang Xiu to surrender to Cao Cao was actually the emperor in Cao Cao's hands , and returning to the imperial court could be described as justified.
And such a good thing can be smashed on Cao Cao's head for no reason, Emperor Xian of Han汉献帝(reign from189AD to 220AD), who did in Xuchang, but made great contribution.
And Liu Biao of Jingzhou has always been an ally of Yuan Shao, and this time he even verbally agreed, but in fact, Did nothing, while people many years later thought that this was a manifestation of Liu Biao's lack of ambition and missed opportunities. In fact, Liu Biao was indeed prepared to go north to attack Cao and go all out to meet Yuan Shao's intentions.
But just as he was about to send troops, there was a fire in his backyard, when there was a Junior official in Jingzhou called Huan Jie桓阶, Huan Jie saw that Liu Biao wanted to send troops to help Yuan Shao, so he went to Changsha长沙 to lobby Zhang Xian张羡, saying that :"Cao Cao fought with rebellions, saved the Empire from danger, and punished the criminal ministers by the order of the emperor, this is a righteous act, now you should fight against Liu Biao, wait for Cao Cao's army, and we will succeed from both inside and outside!"
Zhang Xian, who had served as the Commanderial governor of Guiyang桂阳 , Changsha and Lingling零陵, was deeply popular in Jingzhou, and he had always been at odds with Liu Biao, so he decided to follow Huan Jie's advice and rise to rebel against Liu Biao to support Cao Cao.
At that time, Jingzhou had seven commanderies ,including Nanyang南阳, Nanjun南郡 , Jiangxia江夏, Lingling, Guiyang , Wuling武陵 and Changsha,
Under the leadership of Zhang Xian, the four commanderies in the south of Jingzhou: Changsha, Guiyang , Lingling and Wuling responded one after another, and most of Jingzhou changed in an instant.
Liu Biao was shocked when he heard the news, and hurriedly sent troops to suppress it,how could he still have the leisure to care about Yuan Shao's life and death ?
Soon Cao Cao met the envoy sent by Zhang Xian, and after careful questioning, he secretly rejoiced,Huan Jie and Cao Cao had never known each other, and this time it was obviously stained with the light of Emperor Xian of Han.
However, Cao Cao was confronting Yuan Shao at this time, and there were really no extra troops to support Zhang Xian. Later, Zhang Xian's rebellion lasted for several years, and it could not be quelled, which made Liu Biao anxious.It was not until Zhang Xian's death of illness that Liu Biao recovered the four commanderies in the south of Jingzhou with difficulty, and by this time Yuan Shao had being died of illness, the Battle of Guandu had long been over, and the overall situation in the north had been decided.
Liu Biao also lost the best opportunity to chase the Central Plains, and the Junior official Huan Jie later became an important minister of Wei State like Jia Xu.
The boy who wore the crown of less than 20 years old brought too much invisible wealth to Cao Cao, not only Jia Xu and Huan Jie, but later the officials persuading Liu Biao's son Liu Cong刘琮 to surrender Cao Cao in Jingzhou, Zhang Zhao张昭’s persuading Sun Quan in Yangzhou, this banner with the orthodox Han dynasty written on it, exuding a dazzling light that attracted the hearts of the Empire's scholars, finally overshadowed the famous scholars,overshadowed the title of "3 Councillors in 4 generations".
Yuan Shao lost, to Cao Cao and the boy next to him who was less than 20 years old with a crown on his head.