The conflict was a continuation of the first Indochina war, which was fought when the Vietnamese sought independence from France after World War II. The country was split into two parts — northern and southern — in the Geneva Accords in 1954. The Domino Theory was a metaphor for the spread of communism, as articulated by US President Dwight D. Eisenhower in an April 7, 1954 news conference. Eisenhower expressed concern that communism, which had already become established in China under Mao Zedong, could spread across Asia and even toward Australia and New Zealand: Eisenhower and later American leaders, including Richard Nixon, used this theory to justify US intervention in Southeast Asia, including escalation of the Vietnam War. Although the anti-communist South Vietnamese and their American allies lost the Vietnam War to the communist forces of the North Vietnamese army and the Viet Cong, the Domino Theory did not come into play in Asia. Australia and New Zealand never considered becoming communist states.
In 1956, when elections that were to be held in Vietnam in accordance with the Geneva Conference failed to occur, the tension mounted considerably. December 1958 marked North Vietnam’s first invasion into Laos. Though there were already Americans present in the Vietnam conflict, it was not until 1962 when President Kennedy signed the Foreign Assistance Act of 1962, which granted military aid to countries that were "on the rim of the Communist world and under direct attack."
The Vietcong had their first victory of the Vietnam War at the battle of Ap Bac in January 1963, which was followed by the overthrow of Ngo Dinh Diem and an increasingly less stable South