The arrests of David Greenglass (1922 - 2014: Soviet code name "Kalibr") and Alfred Slack (1905 - 1977: Soviet code name "El") were the result of the FBI having arrested and interrogated a vital Soviet courier a month earlier: Harry Gold (1911 – 1972: Soviet code name "Arno"). When Gold began singing, the spies began to fall like leaves of autumn day. The quick read posted to the right concentrates on Gold's fellow chemist, Slack, who had been passing along information to the Soviets since the mid-Thirties, however between the years 1944 and 1945 Slack had been assigned to work in Oak Ridge Tennessee with the Manhattan Project. Greenglass had also been on the Manhattan project, and he was a far bigger catch, for he was the brother of Ethel Rosenberg - it was his testimony that made the case that she and her husband Julius, were Soviet spies.
Seven years after the collapse of the Soviet Union, Greenglass was asked by a NY Times reporter if he would have done anything differently; he answered "Never". He was released from prison in 1960; Slack in '65.
Additional magazine and newspaper articles about Cold War spies can be read on this page.