Nuclear security

Fourth Spy at Los Alamos Knew A-Bomb’s Inner Secrets

Last fall, a pair of historians revealed that yet another Soviet spy, code named Godsend, had infiltrated the Los Alamos laboratory where the world’s first atom bomb was built. But they were unable to discern the secrets he gave Moscow or the nature of his work.

However, the lab recently declassified and released documents detailing the spy’s highly specialized employment and likely atomic thefts, potentially recasting a mundane espionage case as one of history’s most damaging.

It turns out that the spy, whose real name was Oscar Seborer, had an intimate understanding of the bomb’s inner workings. His knowledge most likely surpassed that of the three previously known Soviet spies at Los Alamos, and played a crucial role in Moscow’s ability to quickly replicate the complex device. In 1949, four years after the Americans tested the bomb, the Soviets detonated a knockoff, abruptly ending Washington’s monopoly on nuclear weapons.