Vietnam War: The Vietnam War was a conflict between North Vietnam (supported by communist forces) and South Vietnam (supported by anti-communist forces) with involvement from other nations including the United States.
Domino Theory: The Domino Theory was a belief during the Cold War that if one country fell under communist influence or control in Southeast Asia, neighboring countries would also fall like a row of dominoes.
Gulf of Tonkin Incident: The Gulf of Tonkin Incident was an alleged attack on U.S. Navy ships by North Vietnamese forces in 1964, leading to increased American involvement in the Vietnam War.