VENONA Break-in
On 20 December 1946, Meredith Gardner of the VENONA Project of the US Army’s Signal Intelligence Service (commonly called Arlington Hall, which would become the National Security Agency) made the first break into the Soviet cryptographic code, revealing the existence of Soviet espionage in the Manhattan Project. NSA : VENONA Document Archive
Tagged 1946, Army SIS, Code Breaking, Espionage, Manhattan Project, Meredith Gardner, NSA, SigInt, VENONA