Han Shu immigrated to Hanzhong.

From the strategy of the Northern Expedition, Jiang Wei not only did not change Zhuge Liang's deployment, but carried it forward. Judging from the military strategy of Hanzhong defense, Jiang Wei really changed Zhuge Liang's Hanzhong defense strategy. Hanzhong is the front line of Shu Han and Cao Wei. Hanzhong was the first one in both the northern expedition of Shu Han and the southern expedition of Cao Wei. Since Liu Bei captured Hanzhong County after the Hanzhong War, Hanzhong has been the gateway of the Northern Expedition of Shu-Han regime, the only place where Cao Wei attacked Chengdu, the frontier base of Shu-Han Northern Expedition and an important strategic location.

Wei Yan was the first governor of Shu Han and Hanzhong. From Liu Bei's time when Wei Yan lived, the defense of Shu Han in Hanzhong was active defense. The so-called active defense is simply "keeping the enemy out of the country." The Hanzhong area of Shu and Han Dynasties is separated from the Guanzhong area of Cao and Wei Dynasties by the natural barrier of Qinling Mountains, which stretches for 800 miles. The so-called Shu Dao is difficult, and it is difficult to go to the sky. That's what I said. At the same time, it is also the only place for Guanzhong to enter Hanzhong and Chengdu. The defense of Shu Han in Hanzhong is the most important.

From Guanzhong to Hanzhong, there are five roads from west to east, namely Qishan Road, Chencang Road, Xiexie Road, Luo Luo Lu Road and Woods Valley Road. No matter from Guanzhong to Hanzhong or from Hanzhong to Guanzhong, these five roads must be taken, and the defense of Shu Han at that time was to set up some defenses at the dangerous points of these five mountain roads. Because the Qinling Mountains are very majestic and the roads are very rugged, these five roads can achieve the effect of "one person can defend them, and ten thousand people can't force them" in some places, so the defense effect of Shu Han was very good at that time, and Cao Wei not only could not attack them, but also had no way to start.

After Liu Bei's death, in Zhuge Liang's time, Shu Han under Zhuge Liang built many defense facilities to defend against the enemy and facilitate the Northern Expedition. For example, Seoul and Lecheng in Hanzhong were all built in Zhuge Liang's time. These two cities are located in the dangerous area in the hinterland of Hanzhong, and together with Yangpingguan at that time, they guarded the throat of Hanzhong. At the same time, Zhuge Liang era still followed the Hanzhong defense strategy of Liu Bei era, defending the enemy from the country and defending the Qinling Mountains from Hanzhong. The advantage of this is that the defense is very strong, and it is difficult for the enemy to come in. The disadvantage is that the troops are scattered and cannot effectively annihilate the enemy's effective strength.

After Zhuge Liang's death, Wu Yi and Wang Ping respectively served as the last round of guarding Hanzhong. By the late Shu-Han Dynasty, Jiang Wei was already the general and the highest military leader of Shu-Han. It is here that Jiang Wei changed Hanzhong's defense strategy, changing the strategy of "going abroad to defend the enemy" that Shu Han had always adopted to "lure the enemy into depth, cut off his food route, surround and annihilate". To put it simply, Jiang Wei's strategy is to abandon the dangerous fortifications in the depths of the Qinling Mountains, shrink his troops, completely recapture Hanzhong, and defend the main cities of Seoul, Lecheng and Hanpingguan. If Cao Wei attacks Hanzhong, let them in, extend Cao Wei's supply line, attack Cao Wei's grain transportation route, rely on the fortified city to avoid danger, and finally surround and annihilate the invading enemy.

Jiang Wei's strategy on the first day seems to have some truth. After all, extending the enemy's route for providing foodstuff is also the reason for winning the war. Guanzhong and Hanzhong are separated by the vast Qinling Mountains, which is very difficult to walk. One of the reasons why Cao Cao failed in the battle of Hanzhong in those years was the problem of providing grain routes and transporting grain. Cao Wei is not short of people and food. If he wants to attack Shu Han, all he lacks is the way to transport food. In 263 AD, after attacking Shu, the defenders of Hanzhong released Wei Jun into Hanzhong according to the strategy of general Jiang Wei. As a result, Seoul, Lecheng and Yangpingguan were all surrounded by Wei Jun, but Jiang Wei was not in Hanzhong at that time, and even Governor Hu Ji was not in Hanzhong. Wei Jun marched and destroyed Shu Han in just a few months.

Jiang Wei is indeed responsible for the demise of Shu Han, but it is not the main responsibility. As the highest military leader of Shu and Han, Jiang Wei has unshirkable military responsibilities, such as guarding against Cao Wei's attack. Hanzhong defenders couldn't think of being so vulnerable, and they were all surrounded by Wei Jun in the city. Wei Jun left the besieged army and continued to attack south. Although Jiang Wei later played a certain role in resisting Wei Jun and prevented Wei Jun from further attacking at Jianmenguan, I didn't expect Wargo to do the opposite, sneak into level tone, take Chengdu directly, and force Liu Chan to surrender, which eventually led to the demise of Shu Han. The main responsibility for the demise of Shu Han lies in the fatuity of the late ruler Liu Chan. Due to Liu Chan's reuse of eunuch Huang Hao, the unhealthy trend in the imperial court is weakening day by day, and Liu Chan has no ability to control everything. Even before the war, Jiang Wei's petition could not be sent directly to Liu Chan, indicating that the information communication channels of Shu Han were not smooth or fell into the hands of villains, which was the main reason for the demise of Shu Han.

From the strategy of the Northern Expedition, Zhuge Liang made five northern expeditions and Jiang Wei made eleven northern expeditions. Jiang Wei has Zhuge Liang's military talent, but not Zhuge Liang's ability to govern the country. War is not only a military issue, but also a political issue. Zhuge Liang managed Shu Han in an orderly way, and his soldiers had enough food, which laid the foundation for the Northern Expedition. Jiang Wei can only play a role in the military and has made no achievements in governing the country and internal affairs. In other words, Zhuge Liang's Northern Expedition has a foundation and strength, but Jiang Wei's Northern Expedition has gradually lost its foundation and strength. Zhuge Liang's Northern Expedition did not suffer great losses. Jiang Wei suffered not only a great defeat in the Northern Expedition, but also several minor defeats. Zhuge Liang's Northern Expedition did not affect the national strength of Shu Han, and the people also supported it very much. However, Jiang Wei's northern expedition led to the decline of Shu Han's national strength, and the people were pale.

Jiang Wei's Northern Expedition was one of the reasons for the demise of Shu Han, but the main reason for the demise of Shu Han was not Jiang Wei's Northern Expedition, but the declining and fatuous Shu Han emperor. In 238, Jiang Wei began the Northern Expedition until the last Northern Expedition in 262. After 24 years, Shu Han still exists for 24 years. If from the death of Zhuge Liang, Shu Han still existed for 29 years after Zhuge Liang's death, it was not a rapid demise, but a gradual process.