Guan Yu always loved the soldiers under his command, but despised the scholars of Jingzhou, and thus had a difficult relationship with the capable generals under his command, such as Pan Jun(潘浚).
Meanwhile, among the generals who defended Jingzhou together,someone held a grudge against Guan Yu, they were Mi Fang(糜芳) and Shi Ren(士仁).
Shi Ren was a native of Guangyang commandery(广阳郡,Basically located in today's Beijing) in Youzhou(幽州,the northeastern Province), belonging to the old subordinates who followed Liu Bei in his early years of rising. He is not from scholar clan.
Mi Fang, on the other hand, was the younger brother of Mi Zhu(糜竺), and his family was a merchant who had lived in Xuzhou(徐州present day southern shandong & northern Jiangsu) for generations, and although their family was quite wealthy, they were not from scholar clan either. They all came from plebeian clans.
Guan Yu has been able to control Jingzhou for many years, relying on the support of this group of plebeian military generals, but Mi Fang and Shi Ren are the other kind of people among them.
More than 20 years ago, Liu Bei couldn't able to take over the post of Provincial Governor of Xuzhou after Tao Qian's(陶谦,former Provincial Governor of Xuzhou) death without the full support of Mi Zhu.
When Liu Bei was sneak attacked by Lyu Bu in the rear(吕布) and lost to Yuan Shu(袁术) in the front, he was in a desperate situation. It was only when Mi Zhu spent all of his family's wealth to help Liu Bei and married his sister to Liu Bei,that Liu Bei came out of his darkest time.
Later on, Cao Cao also tried to draw in the Mi brothers many times, for example, he offered Mi Zhu to be the Commanderial governor of Yingjun(赢郡present day Laiwu City莱芜市 of Shsndong) and Mi Fang to be the Commanderial governor of Pengcheng(彭城present day Xuzhou City of Jiangsu), but neither Mi Zhu nor Mi Fang accepted it, and they single-mindedly followed Liu Bei to join Yuan Shao(袁绍) and Liu Biao(刘表), and wandered around in a state of displacement.
Liu Bei is a man who knows how to be grateful, although Lady Mi has long since passed away, and although both Mi Zhu and Mi Fang are of mediocre ability, Liu Bei still did his best and gave them the rewards they deserved.
After Liu Bei settled in Chengdu, Mi Fang was appointed as the governor of Nanjun(the most important commandery in Jingzhou under Liu Bei’s rule), and Mi Zhu was appointed as the general of Pacifying Han, with a status even above Zhuge Liang, and the treatment is also the highest among the civil and military officials. Liu Bei always treats Mi Zhu as his honored guest, and no one can compare to him in terms of reward and favor.
As getting older older, and getting tired of his long military life, Mi Fang, however, became eager to recoup his early investment after taking up the post of governor of Nanjun. He deviated from his original intention, embezzled military funds and amassed wealth, and had drifted farther and farther away from Guan Yu, who was determined to carry out the Northern Expedition.
Before Guan Yu set out on his expedition, he had ordered Mi Fang to be responsible for raising military supplies, but the storehouse in Jiangling(江陵) city suddenly burst into flames at this time, and a large number of equipments were burnt down. Guan Yu knew that Mi Fang was behind this, so he reprimanded him severely, and the relationship between the two men went down to freezing point.
This matter spread to Jiangdong(eastern Wu), Sun Quan sent a messenger secretly to Jiangling, earnestly persuade and enlighten Mi Fang, Mi Fang was very touched, and from then on has been connected with Sun Quan secretly .
In May 219 A.D., Guan Yu took advantage of the rainy season to lead his commandant, Zhao Lei(赵累), and his son, Guan Pin(关平), marching northward, leaving Mi Fang to guard Jiangling and Shi Ren to guard Gongan(公安), and putting them in charge of supplying the army with provisions and supplies.
However, after the war began, the supplies transferred from these two men were often short of weight and even delayed. Guan Yu was furious when he heard about this and said that he would punish them severely when he returned , so Mi Fang and Shiren were afraid and uneasy.
But Mi Fang is different from Shi Ren, Mi Fang is, after all, Liu Bei's brother-in-law, and, his brother, Mi Zhu, and Liu Bei's relationship is extraordinary, even if Guan Yu really want to punish Mi Fang, he will certainly seek Liu Bei's opinion, and Liu Bei, most likely, will not really put Mi Fang to military justice.
Therefore, after learning of Guan Yu's reaction, although both Mi Fang and Shi Ren were fearful, there was a difference in fear. Mi Fang knew in his heart that the worst he could do was to go back to Chengdu(成都) to retire, and that there was no fear for his life.
Therefore, even if after the arrival of the Wu army, Shi Ren offered the city to surrender, Gongan fell into the hands of the enemy, as long as the Jiangling is still there, Guan Yu at most is temporarily lost the connection with Wuling(武陵) and Lingling(零陵) in southern Jingzhou , he will not be so bad as to lose the base and have no way out.
But the change came in July 219, when Liu Bei was crowned prince in Hanzhong. This event, not only caused great psychological damage to Sun Quan, but also made Guan Yu's official position rise, and he was appointed as the General of front, and was granted a privilege of great freedom - "JiaJieYue"(假节钺).
Since then, Guan Yu had the right to execute those who violated the military law on his own, without the need to ask Liu Bei for permission. This became the last straw that crushed Mi Fang's psychological defense. Knowing Guan Yu's character well, he began to be in a state of desperation, and together with Shi Ren, he fell into a panic like the intertwining of doomsday.
At this time, Lyu Meng(吕蒙) could be said to know the situation in the cities of Jiangling and Gongan very well. Sensing that the time had come, he pretended to be seriously ill and secretly sent a letter to Sun Quan, saying: "Guan Yu's battle in front of him is very tense, but his troops in the rear are still sufficient, because he is afraid of my sneak attack! Now, please call me back to Jianye(建邺present day Nanjing) on the pretext that I am sick. When Guan Yu hears about this, he will surely transfer most of the troops in the city to the front line, and then we can take advantage of the situation to take Jiangling, and Guan Yu can be captured."
Sun Quan then publicly issued a document summoning Lyu Meng back to recuperate. When Guan Yu heard about it, he was really trapped, and began to transfer the troops remaining in Jiangling City to Fancheng in batches, while Lu Xun(陆逊), who was stationed in Wuhu(芜湖), was waiting by the river to greet Lyu Meng.
At this time, Guan Yu was under Fancheng, facing off against Cao Cao's overwhelming army. But what he could never have imagined was that on an invisible front, his only 30,000 navy troops were actually facing all the best soldiers and generals of the two most powerful military group in China at thst time.
Last time, it was Xiang Yu项羽,more than 400 years ago,who was surrounded and suppressed by all-star generals of whole country, with their overwhelming military strength.
Former Yu dies, the Former Han prospers, and Later Yu dies, the Later Han falls.