Prior to the Korean War, both North and South saw themselves as the legitimate government for the entire peninsula. At the time, the North was considered the more advanced, industrialized part of the peninsula, and Kim Il Sung believed that he could win a war with the more rural South. Stalin gave Kim permission for an invasion, and the Soviet premier believed that the war would be small, regional, and over quickly. However, the United States was able to mobilize the United Nations for what was termed a “police action” to intervene on the peninsula. The was would be regional, but it would drag on for years and involve several major world powers.