At the peak of Shu-Han regime, there were Zhuge Liang, Fa Zheng, Li Yan, Jiang Wan, Fei Yi, Zhang Zhao and Wei Yan, and there were Xichuan, Jingzhou, Hanzhong and barbarians in the west. The comprehensive national strength is unprecedented. In Longzhong, he also told Zhuge Liang that at this appropriate time, a general would be sent from Jingzhou to Luoyang, and Liu Beiling's army would go from Yangping to Sichuan to Chang 'an. Zhong Hui and other new generations are still young, and Sima Yi doesn't have much power. Even if Sima Yi is in command, he can block one side and cannot fight on two fronts. Treat Wu Dongan well and don't let him do things from behind. It shouldn't be difficult to capture Chang 'an and Luoyang.
At that time, Wei had just been established, and people's hearts were still unstable. If Liu Bei didn't fight the Yiling War with Wu Dong, but held high the banner of cutting Wei, the people in the Central Plains would still yearn for the Han Dynasty. As an uncle, Liu Bei's slogan of reviving the great man shouted out, and the people of the Central Plains certainly had a great response. Even if Liu Bei died in the Northern Expedition, Zhuge Liang and others could continue to attack Wei.
Because of the failure of Guan Yu's Northern Expedition at that time, Guan Yu had already broken through Fancheng and Xiangyang and entered Henan. Cao Cao wanted to move the capital and escape. At this time, if Liu Bei sent troops to help Guan Yu, or joined forces with Soochow to start from Hanzhong, Cao Cao could not stop it. It's just that history chose the Sima family, failed Guan Yu, and let Shu Han decline. Finally, the Sima family occupied the pigeon nest and completed the reunification.