Zhuge Liang's talent is beyond doubt, he sat dormantly in The Middle Of The World observed the general trend of the world, and when Liu Bei tirelessly invited him out of the mountains, he helped Liu Bei formulate a strategic plan for dividing the world into three parts, and after the establishment of the Shu Han, Zhuge Liang became a minister, and Zhuge Liang became the actual leader of the Shu Han Dynasty in the post-Lord Liu Chan era, taking advantage of the chaos in Cao Wei's political situation to lead the Northern Expedition many times.
During the Northern Expedition, several counties and cities in Longxi were acquired, and the morale of the Shu Han Dynasty was greatly encouraged. However, with Zhuge Liang's death in Wuzhangyuan, after Shu Han lost this towering tree, he also changed from offensive to defensive position, and Sima Zhao felt that the time was ripe when Cao Wei was in power, so he sent Zhong Hui, Deng Ai, and Zhuge Xu to lead 180,000 soldiers to attack Shu Han in three ways.
Cao Wei first destroyed shu han for the following reasons——
First, at that time, Wu Qiang was weak and Shu was weak, and it was easier to annihilate Shu Han. Cao Wei, the thirteen states of the world, monopolized Kyushu, with 660,000 registered households in the country, totaling 4.5 million people, and a total of 400,000 troops. Eastern Wu occupied Jingzhou, Yangzhou, and Jiaozhou, with 520,000 registered households, a total of 2.3 million people, and a total of 220,000 troops, mainly distributed along the Yangtze River to resist Cao Wei. The Shu Han dynasty only benefited the prefecture and Hanzhong, and the population of Hanzhong was also moved to Chang'an by Cao Cao, and there were only 280,000 households registered throughout the Shu Han Dynasty, a total of 940,000 people, and a total of 100,000 troops, mainly distributed in Nanzhong and Hanzhong, from the perspective of comprehensive strength, Cao Wei was twice that of Eastern Wu and 5 times that of Shu Han.
Moreover, the Shu Han of that period was close to collapse, and after Zhuge Liang's death, Jiang Huan took power, and he followed Liu Chan's defensive policy, only defending and not attacking for more than ten years. After Jiang Wei took the throne, he frequently raised troops to carry out a total of 11 northern expeditions, exhausting the national strength of the Shu Han, and the "Chronicle of the Three Kingdoms" records that "the dimension of the troops, the Shu people are sad" is the true portrayal of that time. At this time, during the reign of Emperor Wu Jing of Eastern Wu, he was lightly enriched, and the country lived and worked in peace and contentment, and there was a vague trend of ZTE. It would be easier to annihilate the Shu Han in contrast between the two countries.
Second, Shu has many mountainous areas, and mountain combat is convenient for key breakthroughs. The State of Wu had a dangerous obstacle to the Yangtze River, and when Cao Cao was on the southern expedition, he once wanted to conquer Jiangdong, but because most of the soldiers were northerners and were not good at water warfare, their disobedience to water and soil led to a large area of illness within the army, which led to the defeat of Chibi, and finally the outbreak of plague, the soldiers were killed and injured. At this time, there was no shipbuilding base in Cao Wei's territory, nor was there a general who was good at commanding water warfare, and during Cao Pi's reign, he had launched three eastern expeditions but all of them were fruitless, and he could only sigh that "although Wei has thousands of armed horses, it is useless."
Although the Shu Han side has lofty mountains as a barrier, the territory of Yizhou is also fertile, and the people can be self-sufficient. However, because the Shu Han Army was small and small, they could not cover all aspects of such a large area, and more often they sent seriously ill people to garrison dangerous checkpoints, such as Yangping Pass, Sword Pavilion and so on.
But the weakness of the Shu Han was also here, because they only had infantry, and Cao Wei was not short of infantry and warhorses, and Cao Wei had a great advantage in the comparison of services and numbers. As long as the Wei army conquered the Shu Han stronghold, it could send cavalry to drive straight into the hinterland of Shu Han, and after annexing Shu Han, it would be able to get a huge population and shipyards here, then Cao Wei's size would be greater and stronger, and it was only a matter of time before Eastern Wu was annihilated. Therefore, Sima Zhao, the actual ruler of Cao Wei, believed, "It is advisable to take Shu first, and after three years, in the trend of Bashu going down the river, land and water will advance together, and this will destroy Yu Dingyu and annex Han and Wei." ”
Third, there were problems with the defense of the Shu Han. When Liu Bei took a place in Hanzhong that year, many generals thought that Hanzhong Taishou would be Zhang Fei, because Zhang Fei's resume and military ability were most in line with this position. However, Liu Bei forcefully handed over this position to Wei Yan, and asked Wei Yan in front of many colleagues how to be responsible.
Wei Yan replied to Liu Bei in front of all his colleagues, if Cao Cao personally led the troops to invade the territory, then I would defend him from the gates of the country for the great king; if it was other generals who led the troops to invade the territory, then I would annihilate them for the great king! Liu Bei was very satisfied with Wei Yan's answer, and it turned out that Cao Wei had sent large armies to attack wei many times during the more than ten years that Wei Yan had been defending Hanzhong, but in the end he did not get a bargain, and more often the loss of troops would retreat.
Wei Yan's defensive arrangement for Hanzhong was to arrange for a large army to garrison Yangping Pass, and then send the rest of the troops to garrison various important hills in Hanzhong, and several units showed a cornering trend, if the enemy army could assist each other when they attacked, and rely on the dangerous terrain to fight a war of attrition with the Wei army. The Shu Han side occupied favorable terrain in its own territory and the supplies were very sufficient, but the long Cao Wei front meant that the cost was very high, as long as their supplies were not timely or they could only retreat after being cut off by the Shu army, then the Shu army could also take advantage of the victory to pursue and expand the results. After Wei Yan's death, whether it was Jiang Huan or Wang Ping, they continued Wei Yan's deployment, and Hanzhong was firmly controlled by Shu Han.
It is recorded in the Romance of the Three Kingdoms that Jiang Wei believed that Wei Yan's policy was wrong to guard the sieges, and although it was in line with the meaning of the "heavy gate" of the Zhou Yi, it was suitable to resist the enemy and did not gain great benefits. However, if the enemy is heard, all the besiegers gather their troops and gather in the valley, and retreat to the two cities of Han and Le. So that the enemy cannot enter the peace, the subjects will guard the town and defend it. So he moved his army to Tuntian in Dazhong, and he wanted to lure the enemy deeper and gather superior forces to break the enemy, but this also caused the defense of Hanzhong to be empty.
Therefore, we can see that when the Cao Wei Three Roads army took Hanzhong and directly counter-encircled Jiang Wei, Jiang Wei had no choice but to lead his troops to retreat to The Sword Pavilion Xiongguan, hoping to rely on the Shuzhong Trail to resist the Cao army's troops. However, this clock would lead a large army to contain Jiang Wei's main force, while Deng Ai would lead a strange army to Jiangzhou along the Yinping Trail, and after conquering Mianzhu, Liu Chan would surrender, and Shu Han would officially perish.