David Greenglass (born 1922) was recruited into Soviet espionage by his sister Ethel Rosenberg, who with her husband Julius Rosenberg were executed for committing conspiracy to commit espionage in 1953 for providing American nuclear secrets to the Soviet Union. Greenglass shared an interest in Communism with the Rosenbergs. He married Ruth in 1942, and they joined the Young Communist League shortly before Greenglass entered the U.S. Army in 1943. A talented machinist at the Army base in Jackson, Mississippi, Greenglass was promoted to sergeant assigned to the secret Manhattan Project, the wartime project to develop the first nuclear weapons. He was first stationed at the massive uranium enrichment facility at Oak Ridge, Tennessee, and later worked at the secret Los Alamos laboratory in New Mexico. He later told how he slept through the first test of the atom bomb and made artificial diamonds at the laboratory.
In 1950, UK and US intelligence agencies had discovered that a Los Alamos theoretical physicist, Klaus Fuchs, had also been a spy for the USSR during the war. Through Fuchs' confession, they found that one of his American contacts had been a man from Brooklyn named Harry Gold, who had then passed Fuchs' information on to a Soviet agent, Anatoli Yakovlev, who then would pass it on to his controllers in the USSR. Through Gold, the FBI's trail led to Greenglass and the Rosenbergs, who had also used Gold as a courier. When Fuchs was first captured, Julius gave the Greenglasses $4,000 to finance an escape to Mexico. But they went to the Catskills instead and used the money to seek out legal advice.
Greenglass was arrested by the FBI for espionage in July 1950 and quickly implicated his brother-in-law. He testified against the Rosenbergs in court in 1951 as part of an immunity agreement so his wife Ruth could stay with their two children. He told the court, "I had a kind of hero worship there [with Julius Rosenberg] and I did not want my hero to fail..."
During his testimony in 1951, Greenglass related in detail the secrets he passed on to the Soviet Union through Julius and Gold. He described his work on the implosion lenses used for the "Trinity" test and the bomb used on Nagasaki, "Fat Man." At first this was a matter of difficulty for the prosecution, who wanted Greenglass to testify in open court about the secrets he had given—something which would by definition make them no longer "secret." The Atomic Energy Commission decided that the "implosion" concept could be declassified for the trial, and limited all discussion to the weapons used in World War II (fearing that Greenglass may have seen prototypes for future weapons while at Los Alamos). Federal judge Kaufman at first made all spectators and news reporters leave the room when Greenglass began testifying about his "secrets," but ten minutes later invited the news reporters back in, asking them to use their discretion in reporting on Greenglass's testimony. Greenglass also testified that Rosenberg had given the Russians information about the proximity fuse and a speculative space platform which would sit between the Earth and the Moon.
After the testimony, in an odd and unexplained legal action, Rosenberg attorney Emanuel A. Bloch had the Greenglass testimony impounded in the name of "national security" (it would not be released until 1966). During the trial, Bloch claimed Greenglass wanted revenge for their business failure and attempted to discredit his character and testimony (a legal tactic which failed with the trial judge). Greenglass was sentenced to 15 years in prison, served 10 years, and later reunited with his wife.
After his release in 1960, the Greenglasses lived in New York City under an assumed name. In 1996, Greenglass admitted to the New York Times reporter Sam Roberts that he had lied under oath about the extent of his sister Ethel's involvement in the plot, wanting to protect his wife Ruth. At the trial, he testified that Ethel Rosenberg typed his notes to give to the Russians, when it was probably Ruth Greenglass. Soviet intelligence officers later said they believed Ethel was not an active part of Julius's espionage ring, and Greenglass's crude drawings were not very useful to them since they already possessed Klaus Fuchs' superior information. Greenglass explained, "Look, I had a wife and two children. I didn’t care so much what happened to me, but I cared what happened to them.” When Roberts asked Greenglass if he would have done anything differently, he replied, "Never."
- Robert Lamphere and Tom Shachtman, The FBI-KGB War (New York: Random House, 1986).