Vietnam, formerly known as Indochina, was divided into communist and noncommunist countries, North and South Vietnam respectively, during the early 1950s. President Eisenhower began support of the the Diem regime in South Vietnam to fight the spread of communism worldwide - the idea being that a successful communist takeover in one country would influence that countries neighbors, who would in turn "fall" to communism. This principle was known as the Domino Theory.