On this date in 1951, Julius and Ethel Rosenberg were convicted of conspiracy commit espionage and were sentenced to death. They were executed in June 1953, but only after extended protests from left-leaning public figures worldwide that the Rosenbergs were unjust victims of a Communist witch hunt in America, a martyrdom that continued to be celebrated in some quarters well into the 1980s, I remember.
But time has not been kind to these protestations of their innocence; that they were guilty of nothing more than holding unpopular political beliefs. The Rosenbergs were indeed Soviet spies, history has shown. They were part of a spy ring that provided information to the Soviet Union about the American atomic bomb project. The ring included Ethel's brother, David Greenglass, who later confessed that his sister was a sometime courier who also typed their notes, as well as Morton Sobell, who after almost 50 years of vehement denials finally admitted in 2008 that he and Julius did indeed spy for the Soviets, and that Ethel was aware of their work. Decrypts of WWII-era Soviet cables (code-named "VENONA") further showed that Julius was an active Soviet spy, and that Ethel was, at a minimum, supportive of his activities.
Among espionage historians, however, there remains to this day some uncertainty about whether the Soviets "sacrificed" Julius and Ethel at the time of their arrest, in order to allow other, more important spies in America to escape to Moscow. It's still unclear why, at the same time the Rosenbergs were rounded up, the Soviets (who were tipped in advance) warned other 'atomic spies' in America in advance of their impending arrest, including Morris and Lona Cohen (who were couriers for young Manhattan Project scientist Ted Hall), while apparently allowing Julius and Ethel to be captured by the FBI without warning. The Rosenbergs may well have been less important to the Soviets than their notoriety at the time of their trial implied. And yet they were the only civilians executed in America for espionage during the entire Cold War period.