Deng Ai was fond of military affairs. Whenever he saw high mountains and great rivers, he would survey the terrain there and point out the location of military camps, ignoring others' ridicule.
At that time, it was not easy for impoverished farmers to make a name for themselves. Deng Ai lived a plain life for nearly twenty years. Later, he finally became a junior clerk responsible for helping manage farmland. One day, Deng Ai went to Luoyang to report, and had the opportunity to meet Sima Yi, the Grand Commandant of Luoyang. Sima Yi appreciated his talent very much and recruited him as an official in the Grand Commandant's office. Later, he was promoted to be a secretary.
Meeting Sima Yi could be said to be a major turning point in Deng Ai's life.
In the early Zhengshi era (240-249), the Wei kingdom prepared to implement agricultural colonization in the southeast area to store military food supplies and deal with the Wu kingdom. Therefore, Deng Ai was sent to conduct an inspection. Deng Ai inspected from Chen County (now Huaiyang, Henan) and Xiang County (now Shenqiu, Henan) all the way to Shou Chun. After the investigation, Deng Ai put forward two important suggestions: First, dig rivers and canals, develop water conservancy projects to irrigate farmland, increase yield per unit area, and facilitate transportation by canal. Second, implement large-scale military colonization in Huai Bei and Huai Nan. He believed that "the land is good but the water is scarce, which is insufficient to fully utilize the advantages of the land. It is advisable to open up river channels, which can be used to divert water for irrigation, accumulate a large amount of military grain, and also facilitate transportation." Thus, he wrote the "Jihe Lun" to clarify his views. Deng Ai also believed that "in the past, after defeating the Yellow Turbans, we implemented agricultural colonization and accumulated grain in Xuchang to control all sides. Now that three corners have been stabilized, the situation is in Huainan. Every time a large army is mobilized, more than half of the troops are transported, costing hundreds of millions. This is considered a major project. Between Chen and Cai, the soil is good and the fields are excellent. We can save on the rice fields around Xuchang and let the water flow eastward. Let Huabei station 20,000 troops and Huainan station 30,000 troops. With twelve parts of rest, there are always 40,000 troops, both farming and guarding. The abundant water usually yields three times more than the west. Calculating and removing various costs, five million hu can be completed each year as military funds. In six or seven years, thirty million hu can be accumulated on the Huai River, which is enough food for ten thousand people for five years. With this to attack Wu, there is no place we cannot conquer."
After seeing it, Sima Yi was very satisfied and adopted and implemented it. From the second year of Zhengshi.............................