What does "immigrating people to strengthen the border" mean in the strategic measures to strengthen the border and strengthen defense?

Historically, the northern nomads migrated erratically and were good at riding, shooting and maneuvering. They had strong military advantages, and their raids on the frontiers were extremely sudden. As Chao Cuo said, "The Hu people's food and clothing are not the same." If the karma is not attached to the ground, its potential can easily disturb the surrounding environment." Therefore, the Central Plains dynasty was inherently at a disadvantage in defending against nomadic attacks. It could be said that it was impossible to defend against. As long as one point was broken through, the defense would be defeated for thousands of miles. Therefore, it is difficult to achieve the desired effect by carrying out pure military prevention. At the same time; since the border is far away from the interior, it is impractical and difficult to garrison a large number of troops in the event of something happening on the border. Traveling thousands of miles to come to the rescue may not be enough to resist, but may waste people and money and burden the country heavily. Chao Cuo analyzed in his memorials such as "Recruiting People to Move to the Lower Fortress" and other memorials that simply relying on the central government to send troops to defend and fight against the Xiongnu was not the answer, and the continuous levy of grain and troops, the recruitment of corvees, and the rotation of guarding the border would only make the country If we fail to win, the people will have no peace, and the defense will not be effective, and the border crisis cannot be truly resolved. And "immigrating people to the border areas", that is, cooperating with military operations and immigrating to border areas before and after military expeditions, can not only provide material support for military operations, but also enable large-scale immigration to vacant areas after repelling intrusions, thus consolidating the military The conquest has yielded results. Therefore, the planned migration of residents from the central plains to the border areas is of strategic significance for strengthening border defense and stabilizing the border areas.

In terms of economic layout, the Central Plains region, represented by the East, was developed earlier in history and has a narrow population density. Therefore, immigrating from the economically and culturally developed middle and lower reaches of the Yellow River to the border areas is both in line with The law of economic development can also promote the development of border areas and enhance the overall strength of the country. It is a strategic move that serves multiple purposes.