How did the Han Dynasty implement the national defense demand in the process of "moving the people to the real border"?

Chao Cuo suggested in his book "Raising People to Move to the Border" to Emperor Wen of Han Dynasty that the government must consider the needs of border defense when moving to the border: "A pawn in a distant place is one year more vigilant, and I don't know what the enemy can do. It is better to choose a permanent residence, a family, a field and be prepared. In order to do this, the high city is dug deep, with forests and stones and canals, which is a city with 150 steps between the city and the city. The key point is that the way to cross the river is not for China. First of all, for the room, equipped with field equipment, in order to raise criminals and avoid being restored as a residence; Insufficient, raise slaves to atone, and worship the Lord when you lose slaves; Insufficient is the desire to raise people. " The purpose of this is to make settlements become border towns and strategic strongholds against invasion.