*The atomic age arrived slowly, and every scientific step was published and celebrated globally, until 1939. Many of the German physicists were Jewish and were expelled in 1933. Some emigrated to the United States, including Hungarian-born Leo Szilard, Edward Teller, Eugene Wigner, and John von Neumann. Enrico Fermi had emigrated when Mussolini’s anti-Jewish laws threatened his wife, Laura, and his two Jewish children. In December 1938, Fermi was awarded a Nobel Prize for his neutron-bombardment experiments; he and his family left Stockholm for New York, where he joined Columbia University’s faculty. Austrian physicist Lisa Meitner also fled Germany but joined Niels Bohr’s laboratory in Sweden. Meitner’s physicist nephew Otto Frisch, who worked with Bohr in Copenhagen, joined her in Sweden for the holidays. Together they used Einstein’s equation to calculate “the energy release per split atom” of the chemical observations made by Hahn and Strassmann. Their paper on “the atom-splitting process called nuclear fission” was published in London’s Nature, a journal read by scientists worldwide. Armed with the details of the Meitner-Frisch research, Bohr sailed for a term’s collaboration with Einstein at Princeton and with Fermi at Columbia—where in Pupin Hall a second experiment succeeded on 26 January 1939. That week America’s leading physicists met at George Washington University to hear Bohr and Fermi. Their words and equations “created a sensation.” Some scientists left abruptly to phone their home institutions or flee to their laboratories. The energy released from one chain reaction might equal hundreds of pounds of explosives. Within weeks the process of uranium fission was confirmed by studies at Johns Hopkins University, Carnegie Institute in Washington, and the University of California at Berkeley. While Szilard and Walter Zinn worked at Columbia, and the Joliot-Curies worked in Paris, Hahn and Strassmann—along with Max Planck, Werner Heisenberg, and many others—continued to work in Germany. Moreover, Carl von Weizsäcker, one of the best young physicists, was the son of Baron Ernst von Weizsäcker, Ribbentrop’s close associate.

When the militarized use of their nuclear researches was confirmed, Fermi and others resolved to speak with U.S. military and naval officers. His appointment with a navy research scientist, 17 March, coincided with Hitler’s occupation of all Czechoslovakia, the only site of Europe’s uranium deposits. But the admiral he intended to see was too busy, and he was greeted by junior officers, who infuriated him by their contemptuous, ignorant lack of interest. For months, the émigré scientists received reports that all research was now “concentrated in the Kaiser-Wilhelm Institute,” where they worked on uranium.

The letter was hand-delivered to FDR by Dr. Alexander Sachs on 11 October 1939; Sachs had been introduced to Szilard by former Reichstag member Gustav Stolper. According to Martin Gilbert, on 26 September Berlin scientists met in secret to discuss their work on nuclear fission. The German War Office agreed to spend whatever was necessary for the new secret weapon. Hitler was exultant. It is very likely that the émigré community learned of this meeting. Davis, FDR: Into the Storm, pp. 471–85, 509–12; Gilbert, p. 14; Jungk, Brighter Than a Thousand.