As is now generally admitted, a Soviet bomb would not have been achieved for several years more but for the success of Soviet espionage in obtaining … - Robert Conquest

" "

As is now generally admitted, a Soviet bomb would not have been achieved for several years more but for the success of Soviet espionage in obtaining secret information from Western scientists associated with the Manhattan Project. That is to say, political ideas in the minds of certain capable physicists and others took the form of believing that to provide Stalin with the bomb was a
contribution to world progress. They were wrong. And their decisions show, once again, that minds of high quality in other respects are not immune to political or ideological delirium....In the Soviet case, those involved thought they knew better than mere politicians like Churchill. They didn't.