Best Kept Secrets of the Vietnam War: the Untold Story of the Significance of Social Intelligence

By Catie Nolan

Bracken in Nhu Trang in 1966. Courtesy of Jimmy Bracken

Upon returning home from Vietnam in 1969, if you had asked Jimmy Bracken what he did in the Vietnam War, he would have told you that he was “assigned to the Army Signal Corps” [1].  But this was a lie, and Bracken swore to keep it a secret for 25 years following his deployment. In an oral history interview, Bracken reveals his role as a social intelligence gatherer for the Army Security Agency (ASA) in South Vietnam between 1966 and 1969.  Bracken reflects on his experience in Vietnam and claims that he “didn’t really have that much of an impact” [2]. Bracken’s disposition is one not represented in H. W. Brands’ American Dreams.  By primarily focusing on military combat in Vietnam, Brands fails to recognize the role of the ASA in detecting Vietcong communications.  Undercover designations intended to mask soldiers’ identities and NSA policy laws hinder public knowledge on these veterans’ impact on the Vietnam War.  Due to the secrecy and high classification of an operation, its role, and its agents, ASA missions and units were unknown and until recently, have been kept secrets from the public.  The absence of historical documentation to support Jimmy Bracken’s reflection of his role within the social intelligence force of the ASA highlights the NSA’s obstruction of the ASA’s history in Vietnam.  The NSA’s ability to legally obstruct documents by deeming them as classified prevented historians from producing accurate representations of the history of social intelligence in the Vietnam War.

Bracken’s undercover role within the ASA was to gather Signals Intelligence (SIGINT) via radio and provide tactical information to military forces to best execute attacks using the location of VC units.  In Vietnam, the ASA utilized Airborne Radio Direction Finding (ARDF) equipment, “to identify, triangulate and analyze enemy radio communications” [3]. According to William LeGro, the author of Vietnam from Cease-Fire to Capitulation, these ARDF units were the “single most valuable intelligence resource available to American and Allied forces during the war in Vietnam” [4].  ASA units served under a military unit and were codenamed to protect the unit’s true mission; many ASA units had codenames as Radio Research Units [5].  Upon receiving his draft notice in 1965, Bracken registered within the Army Security Agency (ASA), a subordinate group of the National Security Agency (NSA).  Bracken spent a year learning Vietnamese at the Defense Language Institute Foreign Language Center in Monterey, California. This time in Monterey intended to prepare him to translate encrypted Vietnamese messages intercepted via radio that following year.  After landing in Saigon with the 237th Radio Research Group in 1966, Bracken traveled to Nhu Trang with a Morse-code translator and radio repair guide. Bracken recalls that “Not many other people were doing what I was doing” as he reflects on his duty in Vietnam [6].

The difficulty in his job was not only translating a language he had learned in the span of one year, but also finding Vietcong and North Vietnamese radio broadcasts.  Bracken typically remained in the same location, either “in a tent or the back of his pick-up truck, and listen[ed] to the radios,” spending hours a day searching for signals [7].  Bracken recalls his experience in intercepting radio transmissions: “I heard a lot of static… and every now and then, you’d pick up a voice transmission. Most of the time it was just reaching numbers, which was the way they coded their messages” [8].  Bracken usually heard a series of four-digit groupings. Each group would translate into one letter or number (i.e. “1235 = a”) [9]. Most of these messages translated into numbers and were coordinates that the Vietcong was sending to artillery. Bracken would make a tape of the transmissions, then send the tape to one of the larger military bases in Nha Trang or Phu Bai, or to NSA at Fort Meade.  There, cryptologists would “listen to the tapes, transcribe the encrypted messages, and then go back over them” [10]. When Bracken would intercept coordinate communications, he recalls that “sometimes I’d look at those coordinates to make sure it wasn’t where I was sitting, so I didn’t have to worry about ducking” [11]. While James L. Gilbert’s The Most Secret War provides historical analysis on the impact of Radio Research Units, the contents of these transcripts are not available for public view.

Soldier using Ground-based Radio Direction-Finding. Courtesy of US Army (

Enacted in 1959, Public Law 86-36 authorized the protection of names employed by the NSA, as well as classification of the functions of the NSA.  This law also established the National Security Agency “as the principal agency of the Government responsible for signals intelligence activities” and enabled the Agency “to function without the disclosure of information which would endanger the accomplishment of its functions” [12].  The NSA was permitted to withhold any information that could inhibit the Agency’s goal of obtaining social intelligence or achieving a goal involving national security. The Agency prohibited employees from discussing any matter pertaining to their role, mission, or any classified detail involving the NSA. Throughout the Vietnam Conflict, “ASA would designate all of its units as ‘Radio Research’ to shield its presence” [13].  Bracken recalls that his undercover designation was to “the Army Signal Corps,” a military signal gathering effort [14]. Bracken did not actually work for the military, but this cover allowed the NSA to protect its presence in Vietnam. Knowledge of the NSA’s involvement in Vietnam was not available to the public until the 2000s when the National Security Agency released documentation describing social intelligence involvement in Vietnam.  In a declassified report by the NSA released in December of 2007, senior historian Robert Hanyok researched highlights how a “cryptologic communitywide history” began in 1967 but abruptly stopped in 1971, the same year the NSA deployed ASA units in Vietnam [15].  An attempt to record “the Army Security Agency’s official history never got beyond a draft stage” [16]. According to Hanyok, “it seemed the SIGINT [signals intelligence] community simply was uninterested in any thoughtful reflection on its effort during the conflict” [17].  While halting this effort to record history raised suspicions, the NSA was legally entitled to discontinue historical recordings.  Enacted in 1967, the Freedom of Information Act (FOIA) “provides that any person has the right to request access to federal agency records or information,” with the exceptions for “law enforcement and national security records” [18].

In 1964, the amendment of Title III to Public law 88-290 allowed the Secretary of NSA to employ any person and grant them temporary and limited access to classified cryptologic information.  “During any period of war declared by the Congress, or during any period when the Secretary determines that a national disaster exists, or in exceptional cases” the Secretary “may authorize the employment of any person in … the Agency, and may grant to any such person access to classified information, on a temporary basis, pending the completion of the full field investigation and the clearance for access to classified information required by this subsection” [19].  This law allowed NSA to hire “any” civilian and authorized the deployment of NSA employees to Vietnam and control their ability to discuss their role and the information involved [20]. In addition to its ability to recruit employees and grant them access to national classified information, this law marks a significant increase in the power of the NSA and creates a loophole in which troops can be deployed without a congressional declaration of war. The implementation of laws similar to these allowed the NSA to obstruct public access to the NSA’s plans of national security and intelligence, in addition to the recognition of those involved.  The NSA’s motive to inhibit public knowledge of and access to a number of historical documents concerning ASA forces is unclear, their obstruction inhibits historians’ understanding of the significance of social intelligence in Vietnam.

 Historian H. W. Brands omits the involvement of American social intelligence in the Vietnam War.  In response to President Ngo Dinh Diem and US officials in Saigon request for US assistance, John B. Willems of the Department of the Army proposed the establishment of programs “to provide training to the South Vietnamese and at the same time establish US intercept operations in the country in February of 1961 [21].  President Johnson approved the deployment of “secret operations against the Viet Cong” [22]. On May 13th, 1961, the 3d Radio Research Unit’s “entry marked the first time an entire Army unit had deployed to South Vietnam” [23].  This unit was the 400th United States Army Security Agency Operations Unit, “with a cover designation as the 3d Radio Research Unit” [24].  These Army Security Agency personnel were among the earliest U.S. military personnel in Vietnam.  Brands claims that “American troops in Vietnam had functioned chiefly as advisers” until March of 1965 (Brands 140).  Realistically, it only was until May of 1961 that “only individual advisors had been assigned” [26]. Prior to the escalation of the Vietnam conflict and buildup of US forces in 1965, “ASA direct support units began entering Vietnam as part of the Army’s approved force structure” in 1961 [27].  The ASA command was intended to function as a “strictly tactical support role” [28]. Their arrival in Vietnam demonstrated that they would need to quickly reinvent “what they thought they knew about SIGINT” to fit the environment. It was this “extremely hot and humid climate” that Bracken described that would require the implementation of trucks to transport Direction Finding radio equipment and their teams [29].  US SIGINT found itself constantly challenged to “improve its methods and systems” in order to combat the VC [30]. Brands recognizes the US’ difficulty in “the land, the jungle, [and] the sun” of Vietnam environment, but does not address how SIGINT played a significant role within US combat forces “to demonstrate America’s steadfastness” [31].

In addition to misrepresenting US presence in Vietnam before 1965, Brands fails to address the significance of social intelligence in his recounting of the war.  Brands discusses how the Vietnam War was largely fought via combat on the ground and in the air. The absence of recognition for social intelligence forces causes veterans of the ASA to feel their duty was insignificant. Dave Sandelin, an ASA veteran in the Vietnam War, “whose job was to find the enemy through their radio transmissions,” would likely agree with Bracken’s feeling that he did not feel like he did much for the war effort [32, 33].  Bracken’s stated that ASA veterans “could not declare his role or discuss the details of our involvement in Vietnam for 25 years” [34]. Sandelin declared that “There were a lot of people that made great contributions to the U.S. military that never got any recognition” [35].  A cause of these sentiments are the laws like Public law 88-290 and 86-36 that impeded the discussion or release of any information pertinent to these veterans or their involvement in Vietnam (until recently). This lack of public knowledge likely contributes to why the ASA and its veterans received little recognition for its role in Vietnam.  The ASA’s deployment of its first Radio Research Unit in 1961 demonstrates larger US involvement that described in American Dreams, likely because this operation could not be discussed until 25 years after the conclusion of the war.  By this time, much of history of the Vietnam War has already been deciphered by what was already know.

The ASA’s absence from Vietnam War history demonstrates how the supporting factors that contribute to an event can be left out of historical narratives.  The classification of secrets during and following the Vietnam War obstructed historians’ inclusion of social intelligence and its significance within events of the Vietnam War.  Jimmy Bracken’s reflection on his role within the social intelligence force provides insight on the lack of historical documentation of the ASA and its narratives. While social intelligence does not demonstrate as direct an impact as combat forces, combat forces depend on this essential information to efficiently execute military attacks and defense.  Social intelligence forces like the ASA tend to receive less recognition than combat forces in historical recountings due to US policy on the intelligence operations’ classifications, which impeded public knowledge on the existence of these programs and their effects until almost 30 years after the conflict resided.


[1] Phone Interview with Jimmy Bracken, April 25, 2018.

[2] Phone Interview with Jimmy Bracken, April 2, 2018.

[3] Captain Kevin Sandell, “‘Spooks and Spies’ — Local ASA vets tell stories of combat, intel collection,” U.S. Army, last modified November 13, 2017.

[4] Sandell, “‘Spooks and Spies,'” U.S. Army.

[5] Ibid.

[6] Phone Interview with Jimmy Bracken, April 25, 2018.

[7] Phone Interview with Jimmy Bracken, April 2, 2018.

[8] Ibid.

[9] Ibid.

[10] Phone Interview with Jimmy Bracken, April 25, 2018.

[11] Ibid.

[12] “Legal Basis for NSA and Cryptologic Activities,” in Part 1 of U.S. Intelligence Agencies and Activities: Hearings Before the Select Committee on Intelligence, U.S. House of Representatives, Ninety-fourth Congress, First Session, vol. 4, U.S. Intelligence Agencies and Activities: Intelligence Costs and Fiscal Procedures (D.C.: U.S. Government Printing Office, 1975), 374,

[13] James L. Gilbert, The Most Secret War: Army Signals Intelligence in Vietnam (Fort Belvoir, VA: Military History Office, US Army Intelligence and Security Command, 2003), 6,;view=1up;seq=1.

[14] Phone Interview with Jimmy Bracken, April 25, 2018.

[15] Robert J. Hanyok, Spartans in Darkness: American SIGINT and the Indochina War, 1945-1975, The NSA Period: 1952 – Present (2002), 7:455,

[16] Ibid.

[17] Ibid., 456.

[18] U. S. Department of State, “The Freedom of Information Act,” U.S. Department of State Freedom of Information Act,

[19] “Public Law 88-290: Title III – Personnel Security Procedures in National Security Agency,” in Public Law (United States Government Publishing Office, 1964), 169,

[20] Ibid., 169.

[21] Gilbert, The Most Secret War, 4.

[22] Staff. “Vietnam War Timeline.”

[23] Gilbert, The Most Secret War, 7.

[24] Ibid.

[25] H.W. Brands, American Dreams: The United States Since 1945 (New York: Penguin Books, 2010), 140.

[26] Gilbert, The Most, 7.

[27] Ibid., 32.

[28] Robert J. Hanyok, Spartans in Darkness: American SIGINT and the Indochina War, 1945-1975, The Burden’s First Fanfare: American SIGINT Arrives in Republic of Vietnam, 1961 – 64 (2002), 7:125,

[29] Phone Interview with Jimmy Bracken, April 2, 2018.

[30] Robert J. Hanyok, Spartans in Darkness: American SIGINT and the Indochina War, 1945-1975, Xerve’s Arrows: SIGINT Support to the Air War, 1964-1972 (2002), 7:234,

[31] Brands, 145, 139.

[32] Joe Habina. “Intelligence group played key role in military effort.” The Charlotte Observer, November 8, 2014. article9228452.html.

[33] Phone Interview with Jimmy Bracken, April 2, 2018.

[34] Inid.

[35] Habina



Leave a Reply

Your email address will not be published. Required fields are marked *