During the Kennedy administration, the US became minimally involved in a civil war in Vietnam, sending military advisors to assist the South Vietnamese in countering efforts, supported by North Vietnam, to unify Vietnam under a communist government.
Unlike the event that triggered large-scale military involvement in Korea—the invasion of the south from the northern part of a divided country—the episode that triggered a gradually escalating US military involvement in Viet Nam could be described as an isolated attack. North Vietnamese torpedo boats attacked the US Destroyer Maddox, on August 2, 1964 in the Gulf of Tonkin off North Vietnam. Attacks reported to have taken place on the Maddox and another Destroyer, the Turner Joy, on August 4 appear not to have taken place, although this was not known for certain at the time.
President Johnson announced the attacks in a television address to the American people on the night of August 4. The next day he sent Congress a request for “a resolution expressing the unity and determination of the United States in supporting freedom and in protecting peace in Southeast Asia.”
Congress passed a resolution on August 10, now known as the Gulf of Tonkin Resolution, stating that the United States was prepared to use “all necessary steps, including the use of armed force,” as the President determined, to defend states in southeast Asia asking for assistance.
In the light of more recent history of US military intervention overseas, the last paragraph of Johnson’s message asking for the resolution makes interesting reading:
The events of this week would in any event have made the passage of a congressional resolution essential. But there is an additional reason for doing so at a time when we are entering on 3 months of political campaigning. Hostile nations must understand that in such a period the United States will continue to protect its national interests, and that in these matters there is no division among us.