Sun Quan's killing of Guan Yu and the seizure of Jingzhou were the main reasons why Liu Bei launched the Battle of Yiling, so the Battle of Yiling was plainly a war launched by both sides around the issue of Jingzhou's ownership. In 221, Liu Bei declared himself emperor in Chengdu, established the Shu Han regime, one of the Three Kingdoms, and built warships and prepared to cut down Wu.
Back in 219, Liu Beigang defeated Cao Cao in Hanzhong and established himself as the King of Hanzhong. After the Battle of Hanzhong, Liu Bei divided the civil and military officials under his command, and his power also reached its peak. At that time, in addition to Yizhou, Liu Bei also had Nan County, Wuling County, and Lingling County in Jingzhou, which was basically in line with Zhuge Liang's strategic vision of "crossing Jingzhou and Yizhou" originally planned in the "Longzhong Pair".
Thirteen States of the Eastern Han Dynasty (the dark red part is Jingzhou)
In 219, in response to Liu Bei's victory at Yizhou, the former general Guan Yu also launched the Northern Expedition in Jingzhou, encircling Cao Cao's areas of Xiangyang and Fancheng. Suddenly, Guan Yu's army was in a fierce position, and even Cao Cao had to avoid its sharp edge and discuss the matter of moving the capital. However, the good times did not last long, and Sun Quan took advantage of Guan Yu's Northern Expedition to send his subordinates Lü Meng, Lu Xun and others to secretly attack Nan County. After Cao Cao and Sun Quan joined forces to defeat Guan Yu, Guan Yu's Jingzhou Nan Commandery, Wuling, and Lingling all fell into Sun Quan's hands. In 220, Guan Yu's father and son were beheaded after Linfeng was captured by Sun Quan's army. Sun Quan's seizure of Jingzhou and the killing of Guan Yu not only seriously damaged the "alliance" that Liu Bei had previously agreed with Sun Quan, but also made Zhuge Liang's idea of "Longzhong Pair" come to naught.
Therefore, Liu Bei claimed that after the emperor, he immediately attacked Sun Quan, and more than 50,000 people of the land and water armies went down the river and penetrated hundreds of miles into the jingzhou territory. In order to avoid a battle with the Wu army's marine division, Liu Bei ordered the Shu army to abandon all its warships and go ashore. Liu Bei held out with Lu Xun at Yiling in Jingzhou for half a year, but was unable to advance, his morale was low, his logistics were difficult, and he was finally attacked by Lu Xun's fire and was defeated.
Under the rebellion, the Shu army only had to rely on burning armor and grain and grass to block the road, and only then did it reluctantly protect Liu Bei and retreat back to Yong'an.
In the Battle of Yiling, almost all of the troops sent by Liu Bei to go on a crusade were destroyed, and Fu Tong, Ma Liang, Zhang Nan, and Feng Xi were all killed in battle, and Huang Quan, who was guarding the north of jiangsu, was forced to defect to the State of Wei.
Shortly after the Battle of Yiling, Liu Bei died of illness in grief and anger. It can be said that the Battle of Yiling was another major setback after the Shu state lost Jingzhou, which not only shattered the dream of the Shu state to retake Jingzhou, but also made Zhuge Liang's later Northern Expedition have to detour through the distant Hanzhong to send troops.
The mountains and rivers in the north of Yizhou are dangerous and the road is long, which makes Zhuge Liang's Northern Expedition futile many times.
If Liu Bei could win the Battle of Yiling, there were at least three paths to follow:
The best result: unify the South and divide the world
After the Battle of Yiling, Liu Bei may divide his forces to attack the counties of Jingzhou. As long as he regained his foothold in Jingzhou, he had the opportunity to attack Sun Quan in the lower reaches of the Yangtze River. After the pacification of Jiangdong, jiaozhou in the south would also be subordinate to Liu Bei's clique. If things can develop here, China's "Southern and Northern Dynasties" era will come ahead of schedule, and the final result is that Wei and Shu divide the world equally. However, it was difficult to achieve this extent with Liu Bei's troops, because Sun Quan had close ties with the Shi clique in Jiangdong and was dependent on the people.
General result: capture of Jingzhou, strike and peace
The Three Kingdoms stood tall
After the Battle of Yiling, Liu Bei would definitely attack Jingzhou with all his might. At that time, the 7 counties of Jingzhou had evolved into 9 counties, mainly Cao Cao separated Zhangling County and Xiangyang County on the basis of Nanyang County, and the remaining 6 counties of Wuling, Changsha, Lingling, Guiyang, Jiangxia, and Nan County were in the hands of Sun Quan. The defeat at the Battle of Yiling would make it more difficult for Sun Quan to defend Jingzhou, and would also shake the hearts of Eastern Wu's troops. The author speculates that if Liu Bei wins the Battle of Yiling, he may seize the counties of Jingzhou occupied by Sun Quan and then make an armistice with Sun Quan. If Liu Bei's troops were strong enough, they might be able to do so.
Worst result: equal division of Jingzhou, Wushu alliance
If Liu Bei had won the Battle of Yiling, but could not completely defeat Eastern Wu, he might have been able to divide Jingzhou equally, returning to the division of Liu Bei and Sun Quan in Jingzhou after the "Demarcation of Xiangshui" in 214.
The premise is that Liu Bei won the Battle of Yiling, and the two sides agreed to talk about it. Even if the entire Jingzhou could not be obtained, the three counties of Jingzhou that Liu Bei took back were also conducive to the later Zhuge Liang Northern Expedition.
Zhuge Liang could send troops from the Han River valley in Jingzhou, without having to cross the dangerous Qin River and go on an expedition.