Abstract
Alexander Vassiliev's notebooks fill in long-standing gaps in historians' understanding of Soviet nuclear espionage in the western United States during the Second World War and Cold War. Scholars are, in effect, finally able to see some of the most notorious spy cases in modern history from the Soviet side. The notebooks exonerate some individuals who were accused of spying—and whose careers were ruined as a result—while confirming the guilt of others. These revelations include an arguably definitive answer to a question that has been the centerpiece of Cold War controversy for more than half a century: whether the renowned American physicist J. Robert Oppenheimer was, as alleged at the time, “an agent of the Soviet Union.” The new evidence indicates that he was not a spy.