What was the Venona project initiated during World War II?

During WWII, the U.S. Army Signal Intelligence Service initiated a counterintelligence program on February 1, 1943 that lasted until October 1, 1980. Called the Venona project, its purpose was to decrypt messages transmitted by the various intelligence agencies of the Soviet Union. While started when the Soviet Union was an ally of the U.S. during WWII, the program continued during the Cold War, when the Soviet Union was considered an adversary.

Over a 37 year period, the Venona project decrypted and translated approximately 3,000 messages yielding the discovery of the Cambridge Five espionage ring in the United Kingdom and the Soviet espionage of the Manhattan Project in the U.S. The espionage action in the U.S. was launched to support the Soviet atomic bomb development project.

The messages obtained by the Verona project added significant information to the trial of Julius (1918-1953) and Ethel Rosenberg (1915-1953), American citizens who were convicted of spying on behalf of the Soviet Union. The couple were convicted of providing top-secret information about radar, sonar, and propulsion engines and valuable nuclear weapon designs. At the time, the U.S. was the only country in the world with nuclear weapons.

Convicted of espionage in 1951, both were executed by the federal government of the U.S. in 1953. The electrical engineer Julius, and the actress, singer and secretary Ethel, were the first American civilians to be executed in peacetime for such charges.