After capturing Yu Jin and killing Pang De(mighty generals of Wei), Guan Yu began to storm Fancheng(a stronghold on the east bank of Han River).
At that time, the water on the ground was more than ten meters deep, and the city wall was only a few planks away from being completely submerged, with many places collapsed and destroyed. Guan Yu led his warships to surround Fancheng heavily, so that the city was completely cut off from the outside world.
At this time, Cao Ren's troops had only a few thousand men left, and they were also without food, so the army was scattered, and the soldiers were all terrified. At this time, a subordinate said to Cao Ren, “ Now we are in a desperate situation, it's all the will of God, not our own reason. Instead of sitting and waiting for death, we should take advantage of the fact that Guan Yu's encirclement has not yet been tightened, and escape by night on a light and fast boat; that way, although we will lose the city, we will still be able to save the lives of these thousands of people.”
Cao Ren hesitated after hearing this, so he went to seek the advice of Man Chong, the commanderical governor of Runan. But Man Chong said, “Floods tend to come and go in a hurry and cannot last long. I have heard that Guan Yu has already sent his troops to Jia County(only 73km west to Xuchang), causing the entire population south of Xuchang to be terrified. And the reason why Guan Yu doesn't dare to continue northward with his main force is that he is worried that we will sneak up on his rear. If we withdraw now, the large area south of the Hong River(in present day southeastern Henan province) will no longer belong to the imperial court. That is why I advise you, My Lord, to continue to hold fast in order to wait for the right time!” Cao Ren took Man Chong's advice and no longer had the idea of abandoning the city.
In order to boost morale, Man Chong drowned his own white horse in public, and swore an oath with the soldiers, “If we lose this battle, we will be martyred together. If we win, we will share the wealth together!” Only then did the heart of the army stabilize.
Seeing that the defenders of Fancheng were strong-willed, Guan Yu divided his troops to surround Xiangyang, and General of Crossing the Sea, Lyu Chang, likewise stood firm at the city and resisted stoutly.
By this time, the entire Nanjun had all belonged to Guan Yu, except for the two fortified cities of Xiangyang and Fancheng. Officials under Cao Cao, such as Hu Xiu, the provincial governor of Jingzhou, and Fu Fang, the commanderial governor of Nanyang, all chose to surrender.
Sun Lang and others, who had earlier started a rebellion in Luhun, accepted Guan Yu's assignment of offices and armies and returned to their hometowns to recruit and harass Cao Cao.
At this time, Guan Yu's army was in full bloom and his reputation resounded throughout the world. Not only the Nanjun and Nanyang commanderies in the northern part of Jingzhou, but also the counties in Yuzhou, where Xuchang is located, are in turmoil. The defenders are terrified, The people are waving their flags and clamoring, and those who take advantage of the opportunity to rebel are even more prevalent. Even the roving bandits around Liang and Jia counties accepted Guan Yu's seal, raised Guan Yu's banner, and became Guan Yu's subordinates. Cao Cao's rule over the entire south of the Yellow River faced a collapse in an instant. Chen Shou, used five words to describe the situation in his Record of Three Kingdoms, “Guan Yu terrorizes whole china!”(羽威震华夏!)
In the same month that Yu Jin and Pang De were all lost, Cao Cao had made plans to move the emperor and all the officials in the city of Xuchang to Yecheng.
At that time, two of Cao Cao's strategists, Sima Yi and Jiang Ji, came together to meet with Cao Cao and said, “Yu Jin and the others were defeated because they suffered a flood, not because they lost an offensive battle, and they didn't pose too much damage to the country, so there is no need for you, Prime Minister, to be overly anxious. Liu Bei and Sun Quan seem to have a close relationship from the outside, but in reality they are estranged. Guan Yu's victory is something Sun Quan does not want to see, we can persuade Sun Quan to sneak up on Guan Yu's rear, and promise Sun Quan that when the matter is accomplished, he will be granted the entire land of southern Yangtze River, so that the siege of Fancheng will certainly be lifted.”
Cao Cao heeded their advice, so while sending an emissary to visit Sun Quan, he ordered Xu Huang and Zhao Yan, who were stationed at Wancheng, to slowly advance southward with their troops.
Xu Huang's unit, which was mostly made up of new recruits, was originally just a backup unit in case of an emergency. Now, however, it had become the last trump card in Cao Cao's hand, and as such was something that could not be allowed to fail.
If Xu Huang is defeated, not to mention that Cao Ren, Man Chong and Lyu Chang will all have to follow in the footsteps of Xiahou Yuan and Pang De, even Cao Cao himself will not be able to stay in Luoyang. I'm afraid he'll have to run to the north bank of the Yellow River to set up defenses, just like Yuan Shao did back then.
Therefore, Cao Cao, after thinking twice about it, sent all of his own generals, such as Xu Shang and Lyu Jian, to Xu Huang's army to be under Xu Huang's unified command.
Once Xu Huang arrived at Yangling Slope, north of Fancheng, he received another order from Cao Cao. Cao Cao strictly ordered Xu Huang to stay put, not to engage in battle, and that he must wait for all of the reinforcements to arrive before marching in together.
But where would Cao Cao, already at the end of his rope, go to recruit reinforcements? In order to resist Guan Yu, Cao Cao had already gambled his entire fortune.
In the name of Emperor Xian, he issued an edict ordering Pei Qian, the provincial governor of Yanzhou, Wen Hui, the provincial governor of Yangzhou, and Lu Gong, the provincial governor of Yuzhou, to personally lead all of the defenders in their provinces to rush to Fancheng to rescue the city.
However, these people were civil officials after all, and had no experience in organizing an expedition , so their actions were rather slow.
As a close friend, Wen Hui wrote a secret letter to Pei Qian saying, “Don't mope! Be quick now! Observing from the current situation, it must be that the war situation in Xiangyang and Fancheng is very urgent. The reason why the Prime Minister did not issue an urgent order is mainly because he does not want the local officials and citizens to be scared and provoke chaos. I estimate that within a few days, we will receive a secret order from the Prime Minister urging us to advance. By then, not to mention us, even Zhang Liao and other generals will have received orders to move. Zhang Liao and the others have been following the Prime Minister for a long time, and are quick to realize his deeper intentions; if you go later than Zhang Liao and the others, you will surely be chastised at that time.”
When Pei Qian saw the letter, he was so panicked that he immediately abandoned his provisions and set off quickly with light equipment. Soon after Pei Qian really received Cao Cao's secret edict ordering him to gather urgently.
The generals Xiahou Dun, Zhang Liao and Zang Ba, who were defending Hefei, were all transferred to Fancheng.
This time, in order to attract Sun Quan to send troops to pin down Guan Yu, Cao Cao has shown great sincerity. The whole of Huainan, along with the defenders around the Central Plains, have been completely emptied. With no reinforcements outside and no generals inside, Guan Yu took on Cao Cao's army from whole country with his own strength.
"Ah YunChang(Guan Yu), this is all I, Cao Cao, have saved for over 30 years! I don't care about the rebellion! I don't care about the mobs! I don't care about Sun Quan either! Come on!!! Wait for me at Fancheng! Let's fight it out!!!"