1921: W. Friedman appointed Chief Cryptanalyst for the Signal Corps
In November 1921, Friedman, who had served in a radio intelligence section during the War, was hired as the chief cryptographer for the Signal Corps. He was charged with code and cipher development for the Army, and to plan for wartime signals intelligence operations. However, the budget crises of post war cutbacks combined with the passage of a law in 1927 making radio communications intercept illegal in America, brought the code and cipher effort nearly to a halt. To save the effort from extinction, in April 1929, the Secretary of War directed "That the Signal Corps be charged with the duties pertaining to the solution of enemy codes and ciphers and the detection of secret inks in War, in addition to those duties with which they are now charged by the Army and to the interception of enemy radio and wire traffic in war." The War Department was, in effect, tasking its Signal Corps to break the law. Needless to say, the Signal Corps maintained the utmost secrecy regarding these efforts.
After the Black Chamber closed, all cryptographic work became the sole responsibility of the War Department, by both the Army and the Navy. In May 1929, all War Department operational functions pertaining to cryptography and cryptanalysis were brought together under the Army's Chief Signal Officer. Two months later, the Signals Intelligence Service (SIS) was officially organized with Mr. Friedman as its chief. He remained in this position until 1935 when an Army major was assigned as officer-in-charge.
In 1943, the SIS was redesignated the Signal Security Service and later the Signal Security Agency. Responsibility for the SSA was divided between the Military Intelligence Service (MIS) for operations, and the Signal Corps for administration. On 15 September 1945, the Signal Security Agency was reunited again under the Director of Military Intelligence as the Army Security Agency at Arlington Hall, Virginia.