Sobell worked on military and government contracts with General Electric and Reeves Instrument Corporation in the 1940s, including during World War II.

After that he became an advocate of socialist causes, conducting public speaking and traveling to Vietnam (during the war), to East Germany (before the fall of the Soviet Union), and to Cuba.

[4] According to NKGB agent Alexander Feklisov, Sobell was recruited as a spy in the summer of 1944, during World War II when the Soviet Union had become an ally of the United States.

Rosenberg allegedly said that many people were aiding the Soviet Union "by providing classified information about military equipment".

"[7] In 1945 Sobell married Helen Levitov (1918–2002), who brought her daughter Sydney Gurewitz, born during her previous marriage.

[8] After David Greenglass, Ethel Rosenberg's brother, was arrested on charges of espionage, Sobell and his family fled to Mexico on June 22, 1950.

On August 16, 1950, Sobell and his family were abducted by armed men, taken to the United States border and turned over to the FBI.

It was seven and a half months before he was eligible for parole because the Circuit Court of Appeals gave him credit for the time he was in jail after his arrest and before his trial.

[4][9] After his release from prison, Sobell went on the speaker circuit, regaling audiences with his account of being falsely prosecuted and convicted by the federal government.

[11][12][13] In 1974, Sobell published a memoir, On Doing Time, in which he maintained that he was innocent and that his conviction was a case of justice being subverted to serve political goals.

[14][15] In 1978 the Corporation for Public Broadcasting produced a television special that maintained Sobell was innocent of the government charges.

[16] Lawrence Kaplan, a relative-in-law of Sobell's, wrote in a review of On Doing Time that "although the prosecution presented absolutely no proof that Sobell had any connection with atomic bomb research, he was conjoined as a co-defendant with the Rosenbergs to give the impression that an extensive spy ring had been in operation.

He was asked if he had given military secrets to the Soviets during World War II (then a war-time ally of the United States).

Sobell also said that his co-defendant Julius Rosenberg had been involved in spying:[18] In the interview with The New York Times, Mr. Sobell, who lives in the Riverdale neighborhood of the Bronx, was asked whether, as an electrical engineer, he turned over military secrets to the Soviets during World War II when they were considered allies of the United States and were bearing the brunt of Nazi brutality.