Concept
The Venona project was a United States counterintelligence program initiated during World War II by the United States Army's Signal Intelligence Service and later absorbed by the National Security Agency (NSA), that ran from February 1, 1943, until October 1, 1980. It was intended to decrypt messages transmitted by the intelligence agencies of the Soviet Union (e.g. the NKVD, the KGB, and the GRU). Initiated when the Soviet Union was an ally of the US, the program continued during the Cold War, when the Soviet Union was considered an enemy. During the 37-year duration of the Venona project, the Signal Intelligence Service decrypted and translated approximately 3,000 messages. The signals intelligence yield included discovery of the Cambridge Five espionage ring in the United Kingdom and Soviet espionage of the Manhattan Project in the US (known as Project Enormous). Some of the espionage was undertaken to support the Soviet atomic bomb project. The Venona project remained secret for more than 15 years after it concluded. Some of the decoded Soviet messages were not declassified and published by the United States until 1995. During World War II and the early years of the Cold War, the Venona project was a source of information on Soviet intelligence-gathering directed at the Western military powers. Although unknown to the public, and even to Presidents Franklin D. Roosevelt and Harry S. Truman, these programs were of importance concerning crucial events of the early Cold War. These included the Julius and Ethel Rosenberg spying case (which was based on events during World War II) and the defections of Donald Maclean and Guy Burgess to the Soviet Union. Most decipherable messages were transmitted and intercepted between 1942 and 1945, during World War II, when the Soviet Union was an ally of the US. Sometime in 1945, the existence of the Venona program was revealed to the Soviet Union by cryptologist-analyst Bill Weisband, an NKVD agent in the US Army's SIGINT. These messages were slowly and gradually decrypted beginning in 1946.