１９３３年１月，希特勒当上德国总理后，便开始疯狂地推行法西斯政策，对外准备发动侵略战争，并着手研究核武器；对内残酷迫害人民，特别是犹太人，一大批犹太科学家不得已流亡到美国。１９３９年２月，犹太科学家们动员世界著名科学家爱因斯坦给罗斯福总统写信。信中说：核 In January 1933, after Hitler became German Chancellor, Hitler began furiously pursuing the fascist policy of preparing for a war of aggression and proceeding to study nuclear weapons. A large number of Jewish scientists, the brutal persecutors and the Jewish people in China, were forced to flee to the United States. In February 1939, Jewish scientists mobilized the world famous scientist Einstein to write a letter to President Roosevelt. The letter said: nuclear