I just found this titbit about Albert Einstein and his influence on Roosevelt. I never knew that.
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He escaped from Nazi Germany in 1933, where he had been a professor at the Berlin Academy of Sciences, and settled in the U.S., becoming a citizen in 1940. On the eve of World War II, he helped alert President Franklin D. Roosevelt that Germany might be developing an atomic weapon, and recommended that the U.S. begin nuclear research. That research, begun by a newly-established Manhattan Project, resulted in the U.S. becoming the first and only country to possess nuclear weapons during the war. He taught physics at the Institute for Advanced Study at Princeton, New Jersey, until his death in 1955.
this item is interesting about the Manhattan Project.
Manhattan Project - Wikipedia, the free encyclopedia