In the wake of Hitler’s persecution, scientists, philosophers, artists and writers fled Westward, often leaving behind high-profile academic positions of influence. Many ended up in Europe or America, making significant contributions to the Manhattan Project. Some, like Enrico Fermi, architect of the first nuclear reactor tested at the University of Chicago, were already Nobel Prize winners. Though a pacifist, Albert Einstein, also a Nobel winner, warned President Roosevelt of the rising threat of German weapons research. Hitler’s racist agenda drove out many of Germany’s greatest scientific minds, some of whom in turn contributed to his downfall.