Why did Zhuge Liang leave Qishan three times during his five Northern Expeditions?

Zhuge Liang went out to Hanzhong for the Northern Expedition five times from the 6th year after the Shu Han Dynasty until his death in the 12th year of Jianxing, except for the second time he went out to Dashan Pass to besiege Chencang (today's Baoji City) , the fifth time he went out to Baoxie Valley to station troops outside Wuzhangyuan, and the other three times he went west to Qishan Road to attack Longyou. Why was Zhuge Liang so keen on sending troops to Qishan?

This needs to be discussed from various aspects of history, geography and strategy. As early as the 19th year of Jian'an, when Liu Bei replaced Liu Zhang as the commander of Yizhou, Sun Quan sent Zhuge Jin to Chengdu to ask Liu Bei to return Jingzhou. Liu Bei said: "I am planning to attack Liangzhou. When Liangzhou is captured, I will return the entire Jingzhou. To Soochow." Although this is obviously a perfunctory statement, it also shows from the side that the Shu Han's original strategic expansion direction was Liangzhou. Later, the Shu Han Dynasty and Soochow Wu fell out because of Jingzhou. Liu Bei went east to attack Wu and was defeated by Lu Xun in Yiling. The national power was greatly damaged. After the two sides re-allied, Zhuge Liang went south to conquer Nanzhong to quell the barbarian rebellion. Therefore, it was not until the sixth year of Jianxing that he really began to go out to Sichuan to attack Liangzhou.

From a geographical point of view, to the west of Fufeng County in Guanzhong, where Chencang is located, is the Longshan (today's Liupan Mountain) mountainous area. Majestic mountains like the Qinling Mountains form an obvious barrier, but after all, the terrain environment is very different from the Guanzhong Plain, and it forms its own system west of Longshan Mountain. The Shu Han army is good at fighting in the mountains and may have a slight advantage over Cao Wei's cavalry in the Guanzhong Plain. If the Shu Han can occupy Longyou, gradually immigrate and colonize, and then unite with the Western Qiang and other tribes to strengthen the cavalry. In the future, it will be much easier to send troops from Longyou to attack Guanzhong than to leave Sichuan from Hanzhong Shu Road. Logistics are also more convenient.

In addition, among the several roads leading from Hanzhong to the north and crossing the Qinling Mountains, the easternmost Ziwu Valley can lead directly to Chang'an, but the road is long, rugged and dangerous. Wei Yan once advocated dividing his troops by 10,000 and taking the Ziwu Road. A sneak attack on Chang'an was rejected by Zhuge Liang because it was not feasible. Cao Zhen encountered heavy rain when he was taking the Ziwu Road to attack Shu. The plank road was damaged and the army could not cover half of the distance in a month.

The Tangluo Road leads from Zhouzhi, Shaanxi Province in the north to Hanzhong in the south. It is the most convenient route among the several routes. However, it is close to Taibai Mountain, the main peak of the Qinling Mountains, and requires crossing the Great Dividing Range. The mountains are steep and sparsely populated. In the 20th year of Jianxing's reign, Jiang Wei led tens of thousands of troops out of Luo Valley, but to no avail. Both Ziwu Road and Tangluo Road were not suitable for the army to pass due to terrain reasons, especially because they could not maintain the logistical transportation of food and grass after the army left Sichuan.

From the pre-Qin Dynasty to the Han and Jin Dynasties, the two most important roads connecting Bashu Pass were Chencang Road and Baoxie Road. When Chu and Han were fighting for hegemony, Han Xin used a trick to let Fan Kuaiming build the 500-mile plank road in Baoxie Valley, while he and Liu Bang led their troops to Chencang secretly through Chencang Road. Since the two passages were important routes out of Sichuan, the Wei army paid more attention to them and stationed heavy troops in Chencang and He County. Moreover, on these two channels, neither party can maintain strict confidentiality of military operations. As long as the army is dispatched, the other side will soon get the news and prepare their troops for war. During the first Northern Expedition, Zhuge Liang asked Zhao Yun to go out of Baoxie Road and occupy Ji Valley to contain Cao Zhen. During the Second Northern Expedition, they went out to Dashan Pass on Chencang Road to besiege Chencang but were unable to capture it until they ran out of food and had to withdraw. During the Fifth Northern Expedition, after Zhuge Liang repeatedly went out to Qishan and failed to achieve practical results in Longyou, he went out to Baoxie Road to garrison Wuzhangyuan and confronted Sima Yi in Hexian County. It is impossible to achieve any suddenness by sending troops from Chencang Road and Baoxie Road.

The rest is the Qishan Road, which goes west from Hanzhong through Wudu to Qishan, and then conquers the counties of Longyou. This is the furthest away from the hinterland of Cao Wei and is relatively weakly defended. Due to the strategic suddenness of the First Northern Expedition, the three counties of Nan'an, Tianshui, and Anding responded in the early stage and surrendered to the Shu Han, which shocked Guanzhong. However, Emperor Wei Ming sent General Cao Zhen to lead the army to oversee Guanyou, guard Chencang, and lock the Shu Han army's eastward attack on Guanzhong. In addition, he sent the right general Zhang Yu to attack Longxi and captured Jieting, an important area leading from Liupan Mountain to Longxi. Zhuge Liang could only plunder thousands of households in Xi County and Jiang Wei, and hurriedly withdrew his troops. After that, they sent troops to Qishan Road twice, but they only captured the two counties of Yinping and Wudu south of Qishan Mountain, improving the defense situation on the northwest border. But in the end no effective breakthrough could be achieved. Even after Zhuge Liang's death, Jiang Wei led his army westward from Qishan several times, but still failed to capture Liangzhou.

Zhuge Liang and Jiang Wei's strategy of heading west from Qishan and seizing Liangzhou as a new base for the Northern Expedition seemed to avoid reality and strike at falsehood, and had the possibility of success. But let alone the Wei army's heavy deployment of troops in Guanzhong, it was difficult for the Shu Han to hold the counties in Longyou after they captured them. Even if they can defend the four counties of Longyou. It is almost impossible for the Shu Han to use this to increase their strength.

Liangzhou is a remote area in the west, and there are only a few households. Even at the peak of the population in the Eastern Han Dynasty, the total number of Longxi counties in Anding, Tianshui, Wudu, and Longxi was only 59,000 households, with a population of about 270,000. This statistic is based on the fact that in the late Eastern Han Dynasty, there were nearly 10 million households in the country and a population of about 50 million. After the Yellow Turban rebellion, warlord fighting, and frequent famines at the end of the Han Dynasty, the Three Kingdoms totaled only more than 1.22 million households and a population of 5.8 million, which is about 11.6% of the late Eastern Han Dynasty. Roughly based on a proportional estimate, the four counties of Longyou At this time, the population was approximately 6,000 households and 30,000 people. With such a sparse population, even if Zhuge Liang and Jiang Wei were able to occupy the four counties of Longyou, they would not be of much use in supplementing the Shu Han soldiers and providing logistical support. Immigration to farmland cannot be effective in a short period of time. Therefore, in fact, the counties in Longyou are quite useless to the Shu Han, and they are still useless.

What's more, after Zhuge Liang's first Northern Expedition in the sixth year of Jianxing, Cao Wei had begun to pay enough attention to the Shu Han's Northern Expedition from Sichuan, and dispatched famous generals to station heavy troops on the Guanzhong front line. He also made full use of the weakness of the Shu Han army's logistics dependence on the difficult Shu Road and inconvenient transportation, and did not easily engage in a decisive battle with Zhuge Liang, which made Zhuge Liang have to withdraw his troops during several northern expeditions due to lack of supplies. Summing up the previous lessons, Zhuge Liang made his last Northern Expedition during his lifetime. He took out the Baoxie Road to garrison Wuzhangyuan and began to farm, hoping to solve the problem of military food supply and ensure that he could fight the Wei army in Guanzhong for a long time. However, Zhuge Liang died in the end. Withdrawal.

The reason Jiang Wei left Qishan several times later was because he had no chance of winning by leaving Sichuan directly from Chencang Road and Baoxie Road to attack Guanzhong. When leaving Qishan, they could rely on being a native of Longxi in an attempt to contact Zhuhu to increase their strength. The strategic goal was basically changed to expanding the territory and improving the defensive posture. There was no longer any idea of ??attacking Guanzhong to compete for the world. However, the repeated Northern Expeditions were all in vain and almost exhausted the Shu Han's already weak national power.

Historical records say that Zhuge Liang was not happy with his first Northern Expedition and plundered thousands of households in Xi County. It can be seen that his ambition was not only to expand the territory's population, but to annex Cao Wei and unify the world. But the ideal is very full, and the reality is very skinny. Even assuming that the Shu Han can invade the pass and obtain the land west of Xianyang, but in the face of Cao Wei entering the pass from Luoyang and Nanyang Wancheng, the infantry and cavalry army is three times the size of the Shu army. How likely is the Shu Han army to be able to defend half of Guanzhong when there is no danger to defend it? What's more, Zhuge Liang's strategic focus is in the desolate and remote Longxi. It has become his inevitable fate to work hard and fall into the sky.