After the death of Zhang Fei, why did Liu Bei persist in the crusade against Dongwu?

According to the biography of the reflection of Zhang Fei, Liu Bei sent troops to Wu Dong. Zhang Fei should have led ten thousand foot soldiers to join Jiangzhou, but was killed by Zhang Da and Fan Qiang, who took refuge in Wu Dong with Zhang Fei's head. When Chen Shou mentioned the cause of Zhang Fei's death, he quoted Liu Bei as saying: "Punishment, flogging athletes, the road to self-destruction." There are generally two reasons for Liu Bei's Northern Expedition. The first is to avenge Guan Yu, and the second is to recapture Jingzhou, further gain the territory of Dongwu, gain stronger strength to share the world with Cao Wei, and then unify. But for whatever reason, it seems that Liu Bei is very immature. Because no matter from what point of view, it is difficult for Liu Bei to win by improving the national army's crusade in different places, and his opponent is Wu Dong, which has a vast territory. Moreover, Liu Bei's tactics in the battle of Yiling were also full of loopholes. Lu Xun thought that Liu Beihui put all his eggs in one basket and went down the Yangtze River to Jianye, the capital of Soochow. Although the winning percentage is still low, it is still possible to succeed. But Liu Bei chose to go hand in hand with land and water, which shows that Wu Dong was prepared. Even if the battle of Yiling didn't burn out the company's camp, Liu Bei's army would be slowly consumed by Lu Xun's advantages at home sooner or later. Moreover, unlike the History of the Three Kingdoms and the Biography of Zhang Fei, the History of the Three Kingdoms clearly records that after Guan Yu's death, Liu Bei did not immediately decide to attack Wu, but after Zhang Fei's death, Liu Bei "will" go to Soochow. Obviously, Liu Bei got reasons from the death of Zhang Fei that Guan Yu didn't have, and then decided to attack Wu. Therefore, the reasonable explanation should be that after losing Jingzhou, Liu Bei still has a chance and plans to rally. But the death of Zhang Fei made Liu Bei realize that if the whole country did not attack Wu, I am afraid there would be serious consequences. Shu's army is divided into three parts, one from Liu Qi in Jingzhou, the other from Liu Zhang in Yizhou, and a few from Liu Bei. Jingzhou soldiers lost their hometown, and the danger of mutiny was great; Yizhou's soldiers themselves were taken from Liu Zhang and were not completely unified. They need to rely on Jingzhou's army to contain them. Jingzhou soldiers mutiny, Yizhou soldiers naturally difficult to control; After the fall of Jingzhou, the possibility of capturing the Central Plains is greatly reduced, and those veterans who started to follow themselves from Xuzhou, Xiapi and Xiaopei will be extremely depressed. When Luo Guanzhong was writing The Romance of the Three Kingdoms, he once read Zhang Fei's heart: He was furious with Guan Yu's death and ran to Chengdu to threaten that if Liu Bei didn't attack Wu, he would even attack Wu alone, which was a gesture of disowning his eldest brother. Although the content in the novel can't be taken seriously, what is certain is that the hometown has fallen and the military is unstable. Don't forget, in the story of the Three Kingdoms, Guan Yu lost Jingzhou precisely because Lv Meng controlled Guan Yu's hometown relatives after crossing the river in white. At that time, Guan Yu was leading the troops against Coss and Huang Xu in Fancheng, and the soldiers missed their loved ones and were unwilling to play, which led to Guan Yu's inability to mobilize his soldiers. In desperation, I was defeated by Maicheng. This shows how dangerous it is for soldiers to lose their hometown in the future. Besides killing Zhang Da and Fan Qiang of Zhang Fei, we can see that when Jingzhou was in danger, Mi Zhu's younger brother Mi Fang immediately took refuge in Soochow. You know, Mi Zhu was higher than Zhuge Liang under Liu Bei, and Mi Fang's future could not be * * *; Then General Mengda also took refuge in Cao Wei; When Liu Bei was in Bai Di, Han Jia's satrap Huang Yuan also took the opportunity to rebel. This little man also challenged Liu Bei, which well reflected the split state of Liu Bei's camp at that time. It is not easy for generals to surrender or rebel, especially when many generals surrender or rebel at the same time. It must be that the overall momentum of the army and the country has changed dramatically and people's hearts have been in chaos. Although some people discouraged Liu Bei, Liu Bei still insisted on doing his best to explore the north. In this Northern Expedition, Liu Bei led the Jingzhou School, Yizhou School and the Nanman Army lured by the land. Liu Bei needs to take these people away. It is wonderful to destroy Wu Dong or seize Jingzhou, but it is very difficult. Liu Bei was a soldier all his life and could not be ignorant, so he didn't lead some people who were ambitious, promising and capable of rejuvenating the country in the future. Wei Yan, Zhuge Liang and others stayed behind. He wants to take these troops out of Shu, especially those generals and soldiers who may defect, even if they are wiped out in the end. Whether they die on the spot or run away, it is good not to defect in Shu.