32. Editorial Note
The U.S. intelligence community provided some forewarning of the coming general offensive in South Vietnam, although not comprehensive details. An interim report, entitled “Intelligence Warning of the Tet Offensive in South Vietnam,” April 8, 1968, was prepared by a working group of officers from the Central Intelligence Agency, Defense Intelligence Agency, Bureau of Intelligence and Research, National Security Agency, and Joint Staff. Representatives of the group visited Vietnam March 16–23 to collect documents, receive briefings, and conduct interviews.
The working group report indicates that Director of Central Intelligence Richard Helms informed the President’s Foreign Intelligence Advisory Board in February that there had been evidence in January that attacks in the Highlands might be conducted during the Tet holiday. By late January some targets had been identified, and the intelligence had been communicated to senior military and political leaders in both Saigon and Washington. The report continues: “Despite enemy security measures, communications intelligence was able to provide clear warning that attacks, probably on a larger scale than ever before, were in the offing. Considerable numbers of medium- and low-grade enciphered enemy messages were read. … They included references to impending attacks, more widespread and numerous than seen before. Moreover, they indicated a sense of urgency, along with an emphasis on thorough planning and secrecy not previously seen in such communications. These messages, taken with such nontextual indicators as increased message volumes and radio direction finding, served both to validate information from other sources in the hands of local authorities and to provide warning to senior officials. “The report concluded, however, that the evidence was “not sufficient to predict the exact timing of the attack.” This report is in Central Intelligence Agency Files; it is also available on the Internet at <www.foia.cia.gov>.
Individual intelligence reports are in the National Security Agency, Center for Cryptologic History. [text not declassified] Additional reports of enemy preparations and a memorandum entitled “Vietnam Reporting Prior to Tet 1968 Offensive, September 17, 1975, which reviews the pre-Tet intelligence collection are in the Central Intelligence Agency, DO/EA Files, Job 80–0088A, Vietnam Reporting on Tet 1968 Offensive.