Husband and wife Julius (1918–1953) and Ethel Rosenberg (1915–1953) were tried for conspiracy to commit wartime espionage. Arrested in 1950, the Rosenbergs were charged with passing nuclear weapons data to the Soviets, enabling the Communists to develop and explode their own atomic bomb—an event that had been announced to the American public by President Truman on September 23, 1949. As the realization set in that the United States could now be the victim of an atomic attack, the anxieties of the Cold War heightened. Citizens were encouraged to build bomb shelters, school children participated in air-raid drills, civil-defense films (such as How Can I Stay Alive in an Atom Bomb Blast?) were screened, and entire towns conducted tests of how residents would respond in the event of an “A-bomb.”

Meantime, the leak of top-secret information from the Manhattan Project at Los Alamos, New Mexico, was traced to New York City machine-shop owner Julius Rosenberg, his wife, and her brother, David Greenglass. Historian Doris Kearns Goodwin writes that the “short, plump Mrs. Rosenberg looked more like one of my friends’ mothers than an international spy.” Indeed, the case marked the first time American civilians were charged with espionage; and the trial made international headlines. Though the Rosenbergs were only two of many involved in the conspiracy, theirs was the heaviest of the punishments handed down in the cases against the spy ring. For their betrayal and their refusal to talk, the Rosenbergs were sentenced to death; in issuing the sentence, Judge Irving Kaufman accused the couple of having “altered the course of history.” The penalty rocked the world: As Supreme Court Justice Felix Frankfurter put it, they “were tried for conspiracy and sentenced for treason.” They were electrocuted the evening of June 19, 1953, as New York’s Union Square filled with an estimated 10,000 protesters.