Despite American success in preventing the conquest of South Korea by communist North Korea, the Korean War of 1950-1953 did not satisfy Americans who expected the kind of total victory they had experienced in World War II. In that earlier, larger war, victory over Japan came after two atomic bombs destroyed the cities of Hiroshima and Nagasaki. But in Korea five years later, the United States limited itself to conventional weapons. Even after communist China entered the war, Americans put China off-limits to conventional bombing as well as nuclear bombing. Operating within these limits, the U.S. Air Force helped to repel two invasions of South Korea while securing control of the skies so decisively that other United Nations forces could fight without fear of air attack.