Three Soviet spies were at Los Alamos during World War II, stealing atomic secrets—that we know. Now the CIA journal Studies in Intelligence reports on Oscar Seborer, a fourth, previously unknown figure who may have "handed" Soviets the A-bomb formula before defecting to the USSR. Born in New York City in 1921 to Jewish immigrants from Poland, Seborer had three brothers, two of whom also became US moles; all were drawn to Communist Party USA and came from a family connected to Soviet intelligence, per the Jewish Press. Yet Seborer was able to join the US Army in 1942, take an assignment at the Oak Ridge military complex—where the Manhattan Project was headquartered—and get transferred to Los Alamos in 1944.
The FBI learned about Seborer's 1951 flight to the Soviet Union four years later, but kept it hidden to protect Communist Party USA infiltrators who had revealed his defection. Seborer later received the Order of the Red Star, a Soviet military award, and died in Moscow in 2015 under another name. His full espionage exploits remain hidden pending the declassification of more US files, but a Soviet spy is quoted as saying "he handed over to them the formula for the 'A' bomb." The new study also sheds light on the Soviets' ability to detonate an atomic bomb in 1949, four years after America did. "Soviet weapon scientists were receiving a great deal of valuable information," a Cold War expert tells the New York Times. "Espionage ... helped them a lot more than they were willing to acknowledge." (Read more espionage stories.)