The Gulf of Tonkin incident (Vietnamese: Sự kiện Vịnh Bắc Bộ) was an international confrontation that led to the United States engaging more directly in the Vietnam War. It involved both a proven confrontation on August 2, 1964, carried out by North Vietnamese forces in response to covert operations in the coastal region of the gulf, and a second, claimed confrontation on August 4, 1964, between ships of North Vietnam and the United States in the waters of the Gulf of Tonkin. Originally American claims blamed North Vietnam for both attacks. Later investigation revealed that the second attack never happened; the American claim is that it was based mostly on erroneously interpreted communications intercepts.[5][6][7]
On August 2, 1964, the destroyer USS Maddox, while performing a signals intelligence patrol as part of DESOTO operations, was approached by three Vietnam People's Navy torpedo boats of the 135th Torpedo Squadron.[1][5] The Maddox fired warning shots and the North Vietnamese boats attacked with torpedoes and machine gun fire.[5] In the ensuing engagement, one U.S. aircraft (which had been launched from aircraft carrier USS Ticonderoga) was damaged, three North Vietnamese torpedo boats were damaged, and four North Vietnamese sailors were killed, with six more wounded. There were no U.S. casualties.[8] Maddox was "unscathed except for a single bullet hole from a Vietnamese machine gun round".[5]
On August 4, 1964, destroyer USS Turner Joy joined Maddox on another DESOTO mission. That evening, the ships opened fire on radar and sonar returns that had been preceded by communications intercepts which US forces claimed meant an attack was imminent. The commander of the Maddox task force, Captain John Herrick, reported that the ships were being attacked by North Vietnamese boats when in fact, there were no North Vietnamese boats present. While Herrick soon reported doubts regarding the task force’s initial perceptions of the attack, the Johnson administration relied on wrongly interpreted National Security Agency communications intercepts to conclude that the attack was real.[5]
While doubts regarding the perceived second attack have been expressed since 1964, it was not until years later that it was shown conclusively never to have happened. In the 2003 documentary The Fog of War, the former United States Secretary of Defense Robert S. McNamara admitted that an attack on the USS Maddox happened on August 2, but the supposed August 4 attack, for which Washington authorized retaliation, never happened.[9] In 1995, McNamara met with former People's Army of Vietnam General Võ Nguyên Giáp to ask what happened on August 4, 1964. "Absolutely nothing", Giáp replied.[10] Giáp claimed that the attack had been imaginary.[11] In 2005, an internal National Security Agency historical study was declassified; it concluded that Maddox had engaged the North Vietnamese Navy on August 2, but that the incident of August 4 was based on bad Naval intelligence and misrepresentations of North Vietnamese communications.[5]
The outcome of these two confrontations was the passage by U.S. Congress of the Gulf of Tonkin Resolution, which granted U.S. President Lyndon B. Johnson the authority to assist any Southeast Asian country whose government was considered to be jeopardized by "communist aggression". The resolution served as Johnson's legal justification for deploying U.S. conventional forces to South Vietnam and the commencement of open warfare against North Vietnam.