As an important measure to strengthen border defense, what is the significance of "immigration and border consolidation" for developing border areas and consolidating border defense?

It embodies the frontier strategy of "strengthening the frontier" and "solid defense" and conforms to the objective needs of frontier governance. First, it fundamentally solved the difficulties of defending the border and defending the central plains dynasty. With the development of frontier immigrants, settled agricultural bases have gradually formed, and water conservancy projects and road construction have been carried out one after another. Settlers can deal with the enemy for a long time, effectively resist the harassment of nomadic people on the central plains agricultural area, and ensure the safety of the imperial political and economic center. At the same time, it also extended the control power of the imperial court to the frontier, expanded the social foundation for ruling the frontier, and took the first step to achieve great unity and "turn summer into a foreign country." Second, it is conducive to enhancing national defense potential, consolidating border defense, and achieving stability and development in border areas and the mainland. A large number of immigrants settled in the border areas, which promoted the economic development of the border areas, provided an extremely important economic foundation for strengthening military construction in the border areas, solved the problems of population, soldiers and military supplies in the border areas, guaranteed the life of border guards and reduced the pain of moving inland. In this sense, the strengthening of border defense has actually effectively defended the mainland, so "solid border" is also "solid inside".