3. Julius and Ethel Rosenberg
The Rosenbergs were American Communists who spied for the Soviet Union. They passed on relevant information related to the nuclear weapons to the Soviet Union. Inducted into the KGB in 1942, Julius Rosenberg was considered as a top spy of the Soviet Union. However, they were arrested when Ethel’s brother Sergeant David Greenglass implicated them by confessing to spying for the USSR. The Rosenbergs were executed in 1953 by the electric chair.