Venona project

On February 1, 1943, the U.S. Army's Signal Intelligence Service at Arlington Hall in Virginia began studying a stack of encrypted Soviet diplomatic telegrams. Gene Grabeel, a former schoolteacher, and a growing team discovered that Soviet code clerks had reused some of their one time pads, a mistake that made partial decryption possible. Over the following decades about 3,000 messages were partly or fully read. They showed that Soviet intelligence had run hundreds of sources inside the U.S. government and the Manhattan Project during World War II.¹³

The decrypts helped the FBI identify atomic spies Klaus Fuchs and Julius Rosenberg, as well as Theodore Hall, and confirmed that officials such as Harry Dexter White had passed information to Moscow. Because the program was so secret, Venona evidence was never used in court, and prosecutors had to build cases in other ways. The Soviets learned of it early through their own spies, including Kim Philby. The project closed in 1980, and the National Security Agency released the decrypts in 1995, reshaping historians' arguments over the scale of Soviet espionage and the era of McCarthyism.¹²³⁴