Ethel and Julius Rosenberg were the only two American civilians to be executed for the crime of espionage during the Cold War. They denied all charges and insisted they were innocent, but they were executed in New York's Sing Sing Prison in 1953, despite numerous protests in the United States and abroad.
They were convicted of conspiring to steal US atomic secrets for the Soviet Union. The prosecution's case rested mainly on the testimony of David Greenglass, Ethel Rosenberg's younger brother and himself a convicted spy. Greenglass, who worked on the atomic bomb at the top-secret Manhattan Project in Los Alamos during World War II, had been convicted of giving the Soviets information about nuclear research. He was spared execution in exchange for his testimony. He spent 10 years in prison and was released in 1960.
At the widely publicized trial which started on March 6, 1951, Greenglass stated that his sister Ethel had typed notes containing US nuclear secrets, and these were later turned over to the KGB. The notes apparently contained little that was new to the Soviets; but for the prosecution this was sufficient evidence to convict Ethel Rosenberg.
Investigations into the couple's history revealed conflicting evidence that Julius Rosenberg may or may not have had some dealings with a KGB agent.
The Rosenbergs' conviction fuelled Senator Joseph McCarthy's anti-Communist crusade against "anti-American activities" by US citizens. While their devotion to the Communist cause was well documented, they denied the spying charges even as they faced the electric chair. Their defenders said they never stood the chance of a fair trial given the anti-Communist Red Scare that pervaded the United States in the 1950s.
Decades later in the late 1990s, Greenglass admitted that he had committed perjury and involved his sister Ethel, who had apparently been innocent of all charges. Greenglass said he chose to turn in his sister in order to protect his wife.
Many Americans believed the Rosenbergs were innocent, and an emotional grass-roots campaign was waged across the country to try to stop the couple's execution. Pope Pius XII appealed to President Dwight D. Eisenhower to spare the couple, but he refused on February 11, 1953 and all other appeals were also unsuccessful. The couple was executed, with the instrument of their execution being the electric chair. Reports of the execution state that Julius died after the first application of electricity, but Ethel did not succumb immediately and had to be subjected to a total of three electrical charges before being pronounced dead.