Battle of Fancheng - Analysis

Analysis

Guan Yu's campaign failed because Liu Bei and Zhuge Liang did not give enough support to Guan Yu (or were unable to give their support), and Guan had overestimated his own capabilities. After Guan captured Yu Jin, he could have declared victory by restating his military goal as destroying the enemy reinforcement, or he could've continued besieging Fancheng. To return to Jiangling was not a bad option for Guan, because he would have consolidated the gain of the campaign, and avoid the risks involved in a prolonged war. Amongst the alternatives, Guan chose to continue the siege, which also was a reasonable choice for him at the time, if the siege would not be a long one. Although the initial success was brought to him by a natural flooding, it did indeed crush the morale of the defenders, and Guan attempted to capitalize on that.

Guan's blunder was not in continuing the siege, but severing ties with Sun Quan. At the beginning of the campaign, he had sent an emissary to Sun to ask for help, and Sun did so, though the reinforcement he sent arrived at the battlefield very slowly. Guan should have realized that he was not deemed trustworthy by Sun at the time; however, instead of strengthening the alliance, he chose to insult Sun's emissaries and rejected his marriage proposal, then confiscated Sun's food shortage on the border without prior notice. At this point, it should not be hard for one to see that Sun would retaliate. However, Guan was overconfident on his signal towers, which were erected on high grounds along the Yangtze River to watch over the movement of Sun's forces. This move had a devastating effect on Guan's fate (as can be seen in Lü Meng's invasion of Jing Province), but only had limited effect on the battle of Fancheng, because Guan was not affected by the news Sun attacked his rear (Guan Yu set up fortifications to fight Xu Huang instead).

The first mistake that Guan did relating directly to his military operations was the misconception of a quick capture of Fancheng. He did not realize that the flood was only temporary, and that Cao Cao could still send reinforcement after reinforcement if he failed to take the city in a short period of time. There is a strategic mistake which contributed to the mistake mentioned — Guan divided his forces into at least three parts: the vanguard in Jia County, the detachment besieging Xiangyang, and the main army he directly controlled. In doing so, he violated the law of force concentration, and the siege on any single point would be longer than if he concentrated his forces. Then, when Xu Huang arrived the battlefield with some untrained and weak soldiers, Guan should have delivered a crushing blow to his old friend before Xu could even get prepared, but he instead focused on building fortifications and attempted to mimic what Zhou Yu did in the Battle of Jiangling. The last operational mistake is that Guan underestimated his old acquaintance (perhaps Guan actually did a fair evaluation on Xu Huang, as the latter was not highly regarded before the siege of Fancheng). Besides setting up two camps, Guan had 10 layers of barricades facing the direction of Xu's army, but the latter still ordered an attack after he received some elite troops and successfully conquered Guan's camps.

Other historians took a more sympathetic stands for Guan because at the outbreak of the battle, he faced the dilemma of an unfavorable result regardless the offensive was launched or not. In the west, although Liu Bei successfully gained the strategic stronghold, Hanzhong, Liu Bei could not continue his momentum because the population of Hanzhong was drastically reduced as 80,000 residents were relocated into Cao Cao's territories when the latter defeated Zhang Lu years ago. Although the Hanzhong region was still possessed of a sizable population, Liu Bei would face logistic problems had he continued his campaign against Cao Cao, because the latter had asked one of his officers to relocate 50,000 households of Di tribes to Liang Province. Eliminating his reliable platform to Guanzhong, Cao hindered Liu's offensive in the north. Therefore, Guan led his army north in order to keep pressure on Cao, at the same time buying Liu the time to consolidate his gain. However, the unexpected flood had changed Guan's original goal into conquering northern Jing Province, which is a goal that requires Liu Bei's reinforcement from the west, and Sun Quan's entry from the east. Had Guan Yu not made the blunder of destroying the alliance between Liu Bei and Sun Quan, but instead, strengthened it, he might have a chance of succeeding what he started.

The biggest winner of the conflict was Sun Quan, who not only took back Jing Province from the hand of Liu Bei, but also received Yu Jin and his 30,000 elite troops, and most importantly, Sun Quan had secured Nan Commandery, which was very vital for the survival of the future Eastern Wu regime (it took a short time to travel from Jing Province to Yang Province downstream, if Jing Province was not controlled by the same power that controlled Yang Province, the power controlling Yang Province would be facing probable threat from the other party everyday). Cao Cao also secured his domain in Jing province by successfully fending off Liu Bei's attack, but he was more pleased that the alliance between Liu Bei and Sun Quan melted down, however, Cao Cao would die shortly after the war, and was not able to capitalize on that.