1942: Signal Intelligence Service took possession of Arlington Hall.
Excerpted from NSA document - Pearl Harbor Review: Signal Intelligence Service (see link below)
"It should be remembered that SIS was not attached to the Army's intelligence organization. Military Intelligence considered cryptanalysis merely an adjunct of cryptography, which belonged in the Signal Corps. This situation continued until early in the war.
SIS began with purposes other than foreign intelligence; it was to compile systems for Army use and prepare cryptanalysts for wartime operations. Again like its counterpart, SIS produced valuable information almost as a by-product of training and was transformed into a production office for current COMINT."