In July 219, Liu Bei returned to Chengdu after proclaiming himself queen of Hanzhong. Guan Yu was promoted to a former general, was awarded the false festival Yue, led the army to rejuvenate the division, and made the momentum like a tide, until August, when more than 30,000 people were captured in the ban, and his prestige reached its peak. However, in mid-September, the tide of the battle took a turn for the worse. First of all, Xu Huang defeated Guan Yu outside Fancheng, although he suffered a lot of damage, but he withdrew the siege of Fancheng, and only blocked Xiangyang with a naval army to cut off the connection between the two cities. Secondly, Sun Quan sent Lü Meng and Lu Xun to raid Nanjun. Cao Cao had sent someone to convey the news when Xu Huang attacked Guan Yu, but Guan Yu was incredulous and ignored it. Although Guan Yu did not believe it, it still caused serious distress to Guan Yu's army, and as a result, he was defeated by Xu Huang in a fierce battle. Then, Guan Yu confirmed the news of Sun Quan's attack on Nanjun, and had to retreat south, which was already October. From mid-September to October, only more than 20 days, Guan Yu did not expect the situation to take such a sharp turn and fall into a situation where there was nothing to be done.
During the siege of Xiangyang and Fancheng, Guan Yu gave Liu Bei a treasure, that is, the jade seal used by Liu Bei to become emperor in the future. This suggests that once Guan Yu captures Xiangyang and Fancheng, Liu Bei will take greater action, perhaps even before Cao Cao becomes emperor. Although this is only speculation, it at least shows Guan Yu's attempt to achieve a greater victory during the Northern Expedition. However, the situation took a turn for the worse, and Guan Yu had no choice but to retreat south in an attempt to rescue Nanjun. During this period, did he send someone to ask Liu Bei for help?It stands to reason that it should be.
The Chronicles of the Three Kingdoms: The Biography of Lu Xun recorded: "Lu Xun sent generals Li Yi and Xie Jing to lead 3,000 people to conquer Shu generals Zhan Yan and Chen Feng. Lu Xun sent a naval army led by Li Yi, while Xie Jing led the infantry to cut off the dangerous places, defeated Zhan Yan and others successively, and captured Chen Feng alive. When Xu Huang attacked Guan Yu, Cao Cao had already sent someone to convey the news to Guan Yujun, but Guan Yu was incredulous and ignored it. Although Guan Yu didn't believe it, it caused great trouble to Guan Yu's army, and was finally defeated by Xu Huang in a fierce battle. After that, Guan Yu confirmed the news of Sun Quan's attack on Nanjun, and had to retreat south, which was already October. From mid-September to October, the situation was unpredictable, and Guan Yu was unexpected, in a desperate situation, unable to choose the way forward. During the siege, Guan Yu also gave Liu Bei a jade seal that was said to have been fished out of the Han water. This shows that Guan Yu was eager to achieve great success during the Northern Expedition, but he did not expect the situation to change rapidly, resulting in his inability to return to heaven. Liu Bei was well aware of Guan Yu's defeat and had sent people to support, but unfortunately the rescue channel was blocked by Lu Xun and could not be opened from Zigui to Jiangling. As for whether Liu Bei deployed other reinforcements, there is no exact record, but the initial rescue existed, and Guan Yu was defeated too quickly to have more backup to arrive, and finally ended in failure.