The Vietnam War was a long, costly and divisive conflict that pitted the communist government of North Vietnam against South Vietnam and its principal ally, the United States. The conflict was intensified by the ongoing Cold War between the United States and the Soviet Union. A major factor that led President Lyndon B. Johnson to intervene into Vietnam militarily was the fear of communism due to Cold War tensions with communist countries such as China and the Soviet Union. South Vietnam was very important to the U.S. in Asia with it being perceived as a western democratic state.