The Gulf of Tonkin Resolution was a plan proposed by President Lyndon Johnson and ratified overwhelmingly by both houses of Congress that gave the president, as commander in chief, authorization to take any necessary measures to repel attacks and prevent aggression against United States forces in Vietnam. President Johnson used it as license to greatly expand American involvement in the Vietnam War without having to formally declare war.
By August 1964, the United States was actively involved in helping the South Vietnamese government oppose and contain communist forces in North Vietnam. On Aug. 2, while conducting electronic surveillance for espionage purposes in the Gulf of Tonkin, the destroyer USS Mattox was approached by North Vietnamese torpedo boats. After the Mattox fired some warning shots, the torpedo boats fired upon the Mattox. The destroyer received no damage, but retaliatory air strikes badly damaged the Vietnamese boats. On Aug. 4, the Mattox and the USS Turner Joy, another destroyer, reported another attack by the Vietnamese, although afterward they said that the supposed radar contact may have been due to inclement weather. President Johnson took the attack as fact, ordered retaliatory air strikes on North Vietnam and called for the congressional resolution.
The Tonkin Gulf incident and subsequent resolution was the turning point for the escalation of the Vietnam War. Six years later, after President Nixon's unauthorized excursion into Cambodia, the Gulf of Tonkin Resolution was terminated.