The United States went to war with North Vietnam primarily to stop the spread of Communism. The conflict, known as the Vietnam War, was part of the larger Cold War struggle between the United States and the Soviet Union. The U.S. feared that if North Vietnam, which was under communist control, succeeded in reunifying with South Vietnam, it would lead to the domino effect, where other countries in Southeast Asia would also fall to communism. The United States believed in the containment policy, which aimed to prevent the spread of communism, and therefore intervened militarily in Vietnam to support the South Vietnamese government.
