Signals Intelligence had been a part of the Army's warfighting toolkit since World War I, practiced by radio interceptors, code-makers and code-breakers. The first Army organization to take on the function was the Signals Intelligence Service in 1930, led by William Friedman. This organization, which became the Signal Security Service in 1943, and later the Signal Security Agency (SSA), exploited the communications of both Germany and Japan during World War II. Control of communications intelligence collection assets were split between the SSA (under the Chief, Signal Corps), and the theater commanders. This arrangement created significant problems, since it proved impossible to neatly separate the tactical aspects of communications intelligence from the strategic ones.
When the war ended, the SSA was removed from the Signal Corps and reorganized as the Army Security Agency (ASA) under the control of the Director of Military Intelligence. For the first time, Military Intelligence, through the organization of ASA, assumed command of all signals intelligence and security establishments, units and personnel in the Army. The new agency inherited the mission, functions, and assets of the SSA, while adding the communications intelligence and security resources that had previously been at the disposal of theater commanders.
This put the ASA in a unique position. According to its official historian, ASA was "within, but not part of, the overall military establishment." ASA's headquarters at Arlington Hall, Virginia, staffed primarily by civilian experts, controlled the collection activities of all its units through a separate chain of command -- a "stovepipe" approach to organizational management. This vertical command structure, along with the necessary secrecy of its operations, kept ASA apart from the rest of the Army -- a condition which suited the new organization just fine, as it became almost completely self-sufficient. As historian John Finnegan writes, the agency not only conducted its own operational missions, "ASA administered its own personnel system, ran its own school, arranged for its own supplies, and conducted its own research and development."
The initial organizational structure of ASA did not last long. In 1949, all Cryptologic activities were centralized under a national organization called the Armed Forces Security Agency. With command and control going through the Joint Chiefs of Staff, the individual services were therefore relieved of their autonomous control in this field. Oversight of the agency would be on a rotating basis by officers from all services. However, the focus of the agency remained strictly military rather than on national security, and the rotating command impaired administrative continuity. Therefore, in 1952, the National Security Agency, a civilian agency under the Department of Defense, replaced the Armed Forces Security Agency.
Nevertheless, ASA persevered. The agency's primary collection assets were a number of large fixed field stations that stretched from the U.S. to Germany, from Turkey and Africa to the Pacific. While ASA lost most of its original mission and the bulk of its civilian staff to the Armed Forces Security Agency in 1949, the agency restructured itself to meet Army-specific needs. It developed smaller, mobile field units that could support tactical commanders at every level, which became critical with the outbreak of the Korean War in June 1950.
Over the ensuing decade, ASA became the Army's largest single intelligence and security organization. It exercised tight control over its overseas elements through large regional headquarters in Germany and the Pacific, but processing and direction were centralized at its Arlington Hall headquarters, near Washington, DC. From personnel strength of 11,500 in 1952, ASA grew to 18,300 in just five years. New field stations and tactical units cropped up around the world, and the mission of the agency expanded to include electronic intelligence and electronic warfare, acoustical intelligence, and noncommunications-jamming functions. In 1964, the Army Security Agency achieved the status of a major Army field command.