The Atomic Spies Who Were Never Caught

Klaus Fuchs, a German-born British physicist, passed atomic secrets to the Soviets from inside the Manhattan Project for five years. He provided detailed descriptions of the implosion mechanism, the plutonium core, and the Trinity test results. His information accelerated the Soviet bomb program by 1-2 years. He confessed only after being confronted by MI5. Theodore Hall, an even younger physicist (just 19), independently passed atomic secrets to the Soviets but was never prosecuted because the only evidence against him came from Venona decrypts, which couldn't be used in court.