Shortly after the Soviet Union stunned the world by conducting a successful nuclear test in September 1949 and the Chinese Communist Party seized control of that country only a week later, Hoover scrambled to find those responsible for sharing America’s atomic secrets with the enemy. British agents first arrested the atomic engineer Klaus Fuchs and handed him over to the FBI for interrogation. In the course of rolling up Fuchs’s network, they came across Julius Rosenberg and his wife, Ethel, and when they refused to cooperate and name other names, the Justice Department decided to make an example out of them. Hoover refused to divulge the information on the Rosenbergs from the Venona cables, which was ambiguous enough to induce a confession on lesser charges. Instead, the Rosenbergs were portrayed as diabolical spymasters, with evidence so damning it had to be kept secret. The jury found them guilty, and with Cold War tensions high due to the Korean War, the judge followed Hoover’s suggestion to put both Rosenbergs to death. Shortly afterward it came to light that Adrian “Kim” Philby, a British spy who had liaised with Hoover to hunt Soviet agents, was himself a Soviet agent. The discovery humiliated the FBI and cast clouds of doubt over the Rosenberg case.