National delimitation in the Soviet Union was when they drew lines and borders on a map to decide which country or people would live in each area. The Soviet Union was made up of lots of different countries, and the government wanted to make sure that the right people lived in the right places. They did this by deciding which country or people should get each piece of land, or area, that made up the Soviet Union. They drew lines on a map to make this decision, and this process was called national delimitation.