If Jingzhou had not fallen, Zhuge Liang could have helped Liu Bei defeat Cao Wei and unified the whole country. After Liu Bei got Jingzhou and Xichuan, he thought that his army was stronger than Mazhuang, which bred his thought of underestimating the enemy and his arbitrary style. Jingzhou is so important that there are only 50,000 soldiers and horses. Even if Guan Yu doesn't handle it, it's hard for a cautious general to keep it. Worst of all, Liu Bei didn't listen to Zhuge Liang's advice. After Guan Yu's defeat and death, almost all the soldiers in the country attacked Wu, which led to the defeat of Yiling and the burning of the camp. There are few hundreds of thousands of troops left, which makes Shu's military strength plummet. The failure of Guan Yu and Liu Bei was the result of violating Zhuge Liang's established national policy of Longzhong, and Liu Bei regretted it after his defeat.
After Liu Bei's death, Zhuge Liang knew that it was difficult to attack Wei, which was different from when Jingzhou was still there. But Zhuge Liang wanted to realize the last wish of the late emperor (Liu Bei), knowing that he could not, which reflected Zhuge Liang's loyalty. More importantly, Zhuge Liang knew that being satisfied with a couple can last for a while, but not for long. If Shu does not attack Wei, Wei will attack Shu. It is not impossible to defeat Wei with the strength of Shu and Zhuge Liang's courage and ingenuity, even though it is difficult and dangerous to attack Wei from Qishan. Unfortunately, Liu Chan is still young and out of step with the world. He listened to rumors and recalled Zhuge Liang from the front when he made great progress in military affairs. Later, Sima Yi commanded Wei Jun, and Zhuge Liang got into trouble because he insisted on avoiding the war, which led to his death in Wuzhangyuan, which made the strategic decision to attack Wei and Longzhong fall short.