They supposedly kept Albert Einstein out of the Manhattan Project because of his “radicalism”.
Not good, considering the people with real communist connections in the project!!
I remember from the book in ‘Enola Gay’ that when they were looking at Oppenheimer they had the wrong guy. The author of the book stated that a scientist named David Greenglass was an actual Soviet spy, passing atomic secrets to the Soviets, not Oppenheimer.