Army Security Agency

Army Security Agency


The Army Security Agency (ASA) provided the United States Army with signal intelligence and security information from 1945 to 1976. During the 1960s, ASA played a key role in the Vietnam conflict, a role symbolized by the fact that an ASA operative was the first soldier killed in the war.

For almost as long as there has been viable electronic communication, the U.S. military has been concerned with the field of signals intelligence (SIGINT): information gathered from the interception, processing, and analysis of electronic communications. The first SIGINT efforts in World War I were informal, and only in 1930 did the army organize the first permanent SIGINT organization, the Signal Intelligence Service (SIS).

In 1943, the army renamed SIS as the Signal Security Agency, or SSA. On September 15, 1945, less than two weeks after the end of World War II, SSA became the Army Security Agency. Commanded by the director of military intelligence for the army, the newly formed office possessed broad powers, a fact made evident by its wide geographic presence: in addition to untold fixed sites, or field stations, across the globe, it also maintained significant theatre headquarters in both Europe and east Asia.

Four years after its formation, in 1949, the ASA was placed—along with its navy and air force counterparts—under the new Armed Forces Security Agency (AFSA). Though AFSA was a forerunner of the National Security Agency (NSA; formed in 1951), unlike NSA, AFSA had little actual power. Therefore, the reorganization had little effect on ASA operations other than the reassignment of most ASA civilian personnel to AFSA. ASA, meanwhile, continued its duties in the field, and would play a key intelligence role in the conflicts of the 1950s and 1960s.

ASA in Korea and Vietnam

As a result of needs created by the Korean War, ASA expanded its operations, and deployed numerous tactical units to support the army on the ground. The Korean conflict saw the first use of groups and battalions in the ASA structure, a symbol of its growth during wartime. In 1955, ASA expanded its mission to include electronic intelligence and electronic warfare functions that had formerly been the responsibility of the signal corps. Because its role now encompassed more than intelligence and security, it was reassigned from G-2 (military intelligence) to the U.S. Army chief of staff.

The first ASA personnel arrived in Vietnam on May 13, 1961, to set up a post at Tan Son Nhut Air Base in South Vietnam. Assigned to the 3rd Radio Research Unit (RRU), ASA personnel were chiefly concerned with direction-finding (DF) operations to locate Viet Cong transmitters operating in South Vietnamese territory. On December 22, 1961, a Viet Cong ambush outside the capital city of Saigon claimed the life of Specialist Fourth Class James T. Davis, a DF operator who became the first of more than 50,000 American soldiers killed in Vietnam during the next 11 years.

Davis's death pointed up the dangers for the DF operator in Vietnam: because of the difficulties of wave propagation in the thick southeast Asian jungles, the DF operator had to be close to the transmitter to detect it. The solution was an airborne DF platform, the first of which ASA deployed in March 1962. In 1965, as the U.S. presence in Vietnam reached its height, the 509th Radio Research Group replaced the 3rd RRU, and ASA personnel in country numbered as many as 6,000. The agency itself had grown to include some 30,000 personnel, and in 1964 had become a major army field command.

As the Vietnam conflict drew to a close, however, ASA began to contract rapidly. By 1975, reorganization had effectively ended its existence, and it was formally disbanded on the last day of 1976. On January 1, 1977, a new security and intelligence command known as Headquarters, U.S. Army Intelligence and Security Command, replaced ASA.



Bamford, James. Body of Secrets: Anatomy of the Ultra-Secret National Security Agency: From the Cold War through the Dawn of a New Century. New York: Doubleday, 2001.


Army Security Agency Online. < > (December 30, 2002).

Origins of the Army Security Agency and INSCOM. < > (December 30,2002).


Codes and Ciphers
Cryptology, History
SIGINT (Signals Intelligence)

User Contributions:

Considering the covert operations of the ASA in Viet Nam, how many unit or individual citations did the 509th recieve?

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