Let's first look at the territories occupied by various countries during the Three Kingdoms period. There are thirteen states in the world, and Wei monopolizes Kyushu, namely, Lianghe, Hehe, Hehe, Seclusion, Hebei, Qinghai, Xu and Henan. Wu occupied Jingzhou, Yangzhou and Jiaozhou, and only Yizhou. As far as population is concerned, Wu's is over, while Wei's population is ten times.
In terms of economy, Wei occupies the most prosperous area in the Central Plains, Wu occupies the south of the Yangtze River and the coastal areas, with fertile land, while Yizhou, occupied by Shu Han, has more mountains and less cultivated land. The most important thing is the topographical factors of Shu Han, such as mountains and mountains, the difficulty of Shu Dao and the difficulty of heaven. On the other hand, Wei and Wu are located in the Central Plains, one in Jiangdong, where water conservancy and transportation are very convenient. Under such different circumstances, how can Shu Han recover the Han Dynasty in both countries?
Shu Han was located in Yizhou, and most courtiers came from Liu Bei's Jingzhou Group and Yizhou local strongmen. After Guan Yu lost Jingzhou, there was only one acre of land left in Yizhou, and the talent reserve came entirely from the local area, while Cao Wei occupied two-thirds of the land in the world, and the talent reserve came from various States and counties. Sun Wu occupies the land of Jiangdong, and the number of talents is not as good as that of Cao Wei, but it is more than enough compared with Shu Han.
Yizhou is located in a place with mountains, and the traffic is extremely inconvenient. Many places can only rely on plank roads. In ancient times, the focus of the war was that the soldiers and horses did not move food and grass first. With the landform type of Shu and Han, grain and grass often can't keep up, which leads to tight war. Moreover, in the land of Shu Han, the cultivated land area is really small, and the grain and grass reserves are insufficient, so it can't stand a large-scale war.
In addition, there are contradictions among various camps of Shu and Han, such as Liu Bei's primitive class, Jingzhou Group and Yizhou local strongman Dongzhou Group. Just looking at the contradiction between Wei Yan and Yang Yi, we can see that both of them are talents. Wei Yan is a general in the west, a satrap in Hanzhong, a strong soldier and a warrior, but he is arrogant and difficult to get along with others.
Yang Yi, on the other hand, served as prime minister for a long time and joined the army, taking on heavy work in the army. But he is impatient and narrow-minded, and the forces of both sides are incompatible. If Zhuge Liang had not gone north, the direct contradiction between them might have had a greater impact in the increasing friction.
It is precisely because of the seriousness of these problems that Zhuge Liang exerted great pressure on Cao Wei through the constant Northern Expedition, constantly consuming Wei's strength, and at the same time draining the internal contradictions to transfer the influence brought by the contradictions between internal groups and talents. If Zhuge Liang does not insist on the Northern Expedition to recuperate, the strength of Cao Wei will be unprecedented, and the demise of Shu Han will be greatly advanced under the great pressure of internal contradictions and external enemies.