Video: 'President Johnson's Vietnam Address, 8/4/64. MP498.'

(Tuesday, August 4, 1964, 11:34 p.m. EDT; during the Vietnam War, part of the Indochina Wars and the Cold War) — President Lyndon B. Johnson announced tonight that he had ordered retaliatory action against gunboats and “certain supporting facilities in North Vietnam” following renewed attacks on American destroyers in the second Gulf of Tonkin incident.

Video: 'LBJ's Phone Calls: A Pivotal Day, August 4, 1964 - ABC News Nightline - 7/18/1997'

In a televised address, Johnson stated that air attacks on North Vietnamese ships and facilities were underway as he spoke. He had authorized a retaliatory airstrike from the carrier USS Ticonderoga and urged Congress to take action.

Video: 'PBS - American Experience - LBJ (1991) 2of4' (Johnson announcement, Aug. 4, 1964, at 37:13)

The President’s order came after the second Gulf of Tonkin incident, which would propel the United States into a large-scale commitment to the Vietnam War. This incident involved the commanders of two U.S. Navy destroyers believing they had been attacked in an event that “probably never occurred.”

Video: 'Vietnam a Television History Part 4 LBJ Goes to War 1964 65' (Johnson announcement, Aug. 4, 1964, at 15:06)

The USS C. Turner Joy and the USS Maddox reported that evening that they were being attacked by North Vietnamese gunboats.

Video: 'Vietnam: A Television History (Ep-6) America's Enemy (1954-1967)' (Johnson announcement, Aug. 4, 1964, at 14:39)

Three days later, Congress overwhelmingly authorized the use of American force in a conflict that would ultimately claim the lives of over 58,000 Americans and one million Vietnamese.

Video: 'Vietnam: The Ten Thousand Day War - Days of Decision [3/13]' (Johnson announcement, Aug. 4, 1964, at 35:59)

Nearly 40 years later, declassified information revealed that President Johnson was skeptical about the second attack. The National Security Agency concluded, after analyzing 140 formerly secret documents, that although there was no doubt about the August 2, 1964, attack on the Maddox, there had never been a second attack.

Video: '45 85 Part 10' (Johnson announcement, Aug. 4, 1964, at 1:56)

NSA historian Robert J. Hanyok found that, “In truth, Hanoi’s navy was engaged in nothing that night but the salvage of two of the boats damaged on August 2. SIGINT reports which suggested that an attack had occurred contained severe analytical errors, unexplained translation changes, and the conjunction of two unrelated messages into one translation.”

The consensus among historians is that there was no attack on the American ships today. However, Johnson believed an attack had occurred and ordered retaliation based on flawed intelligence, setting the stage for the extensive American involvement in the Vietnam War.