"No Attack Happened That Night"
A report from the National Security Agency states that the attack on U.S. ships in the Gulf of Tonkin used as the rationale for escalation of the war in Vietnam never happened.
Analysis Casts Doubts on Vietnam War Claims
"An article written by one of the agency's historians for its classified publication, Cryptologic Quarterly, declaring that his review of the complete intelligence shows beyond doubt 'no attack happened that night.'
Claims that North Vietnamese boats attacked two warships that Aug. 4 - just two days after an initial assault on one of those ships - rallied Congress behind Johnson's buildup of the war. The Gulf of Tonkin resolution passed three days later empowered him to take 'all necessary steps' in the region and opened the way for large-scale commitment of U.S. forces...
The article, by NSA historian Robert J. Hanyok, reviews signals intelligence, or SIGINT, from that time and concludes top administration officials were only given material supporting the claim of an Aug. 4 attack - not the wealth of contradictory intelligence...
'In truth, Hanoi's navy was engaged in nothing that night but the salvage of two of the boats damaged on 2 August,' Hanyok wrote.
He said 'the handful of 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. This latter product would become the Johnson administration's main proof of the Aug. 4 attack.'"
Update: Here is the original 2001 article [pdf]