According to historical records such as The History of the Three Kingdoms, Zhuge Liang conquered the Central Plains five times in his life. During the first Northern Expedition, Zhuge Liang sent troops to three counties in Longxi (Tianshui, Nan 'an and Anding), and gained first and then lost. Longxi three counties are located in Gansu province; During the Second Northern Expedition, Zhuge Liang surrounded Chencang, which was located in Shaanxi Province, near Gansu Province. In the third Northern Expedition, Zhuge Liang occupied Wudu and Yin Ping counties, which were mainly distributed in Gansu Province in the fourth Northern Expedition. Zhuge Liang sent troops to Qishan in the east of Lixian County, Gansu Province. During the fifth Northern Expedition, Zhuge Liang sent troops to Wuzhangyuan, Qishan County, Baoji City, Shaanxi Province. It can be seen that Zhuge Liang attacked Cao Wei five times, and most of the battlefields took place in Gansu today, not Guanzhong or the Central Plains. The author believes that Zhuge Liang called for the northern expedition to the Central Plains, often for the following reasons. On the one hand, in my opinion, this is because after Guan Yu lost Jingzhou, Shu Han lost the platform to directly attack the Central Plains.
In AD 2 19, Guan Yu, who was guarding Jingzhou, launched the battle of Xiangfan. In this battle, Guan Yu surrounded Xiangfan. If all goes well, Guan will lead the army into the Central Plains. However, when Monroe attacked Jingzhou, not only Jingzhou fell, but Guan Yu was also defeated and killed. After the fall of Jingzhou, it was almost impossible for Shu Han to attack the Central Plains directly from Yizhou. On this basis, it is considered that the basis of attacking the Central Plains in Han Dynasty is the Central Plains. However, after Wei Yan put forward the meridian valley plan, Zhuge Liang still did not focus on Guanzhong, but repeatedly attacked Longyou and Longxi. In my opinion, this is mainly because Gansu is a relatively weak area of Cao Wei, and the attack difficulty is relatively low. On the other hand, today's Gansu Province mainly belongs to Liangzhou. Being far away from the Central Plains, there were Qiang and Hu tribes in the Three Kingdoms period at the end of the Han Dynasty, and it was difficult for the Eastern Han Dynasty, Cao Wei and even the Western Jin Dynasty to control this area for a long time.
Third, at the end of the Eastern Han Dynasty, Dong Zhuo, Ma Chao and other governors had close ties with Liangzhou. After Cao Cao surrendered to Ma Chao and Han Sui, Song Jian claimed that Shou Ping was Hanwang and assembled troops in Wuhan (now Linxia, Gansu). In my opinion, this shows that the rebellion in Liangzhou is more frequent. In the view of Zhuge Liang, the prime minister of Shu and Han Dynasties, this is naturally the weakness of Cao Wei. When attacking these areas, Cao Wei's strength was relatively weak. You can also unite with the local Qiang and Hu nationalities to achieve twice the result with half the effort. For Cao Wei, although Governor Liang Yong was appointed to be responsible for the military affairs of Gansu and Shaanxi provinces, he was stationed in Guanzhong, and his center of gravity was not in Gansu at first. On this basis, when Zhuge Liang made his first northern expedition to Wei, the three counties of Longxi (Tianshui County, Nan 'an County and Anding County) were smooth and smooth. If Ma Su hadn't lost the street pavilion, Longyou would have fallen into the hands of Shu Han.