Sachs hands Roosevelt a letter about uranium; the president tells an aide, "this requires action"
By the fall of 1939, Leo Szilard feared German scientists were racing to weaponize a discovery physicists on both sides of the Atlantic already understood: that splitting a uranium atom released enormous energy. Szilard drafted a letter in August, Einstein signed it, and economist Alexander Sachs finally carried it into the Oval Office on October 11, 1939. Roosevelt met Sachs again the next morning, and after hearing his Napoleon-and-Fulton anecdote, turned to his aide and said, "Pa, this requires action." Eight days later he created the Advisory Committee on Uranium, the first government body devoted to the uranium question that later grew into the Manhattan Project.
Roosevelt's response created the first federal body ever assembled to weigh a nuclear weapons program, a decision only Roosevelt, as president, was positioned to make. That $6,000 committee grew into the Manhattan Project, which built the bomb that ended the war with Japan.
QWhy did Szilard's own chain reaction patent stay hidden from the world for over a decade?
Szilard filed for the neutron chain reaction patent in Britain in June 1934, and it was granted in March 1936, but almost nobody read it. Under section 30 of the UK Patents and Designs Act of 1907, he assigned it to the British Admiralty specifically to keep it classified. He later explained the reasoning bluntly: having read H.G. Wells's novel The World Set Free in 1932, he knew exactly what a chain reaction could mean for weapons and did not want the patent published where any physicist could find it. The assignment worked, keeping the patent secret until 1949, when Britain repealed the relevant part of the 1907 law.
QWhat happened to the stenographer who typed Szilard's warning about city-destroying bombs?
Janet Coatesworth, a young departmental stenographer at Columbia, took dictation from Szilard for the English version of the letter to Roosevelt. As he described bombs powerful enough to level a port city, she became convinced she was taking dictation from a madman. Szilard closed the letter with 'Yours truly, Albert Einstein,' which did nothing to change her mind, since the words were coming from Szilard's mouth, not Einstein's. She typed it anyway, and that draft, mailed to Einstein's home on Long Island for his signature, became the actual document that reached Roosevelt's desk in October 1939.
QHow far off was the 1939 estimate of how much uranium a bomb would need?
The letter Einstein signed told Roosevelt that a bomb might be 'too heavy for transportation by air,' because at the time physicists believed several tons of uranium would be required to sustain a chain reaction. That estimate held for seven months. In early 1940, a breakthrough calculation in Britain, the Frisch-Peierls memorandum, revised the necessary critical mass down to less than 10 kilograms, small enough to fit in a bomb casing an aircraft could carry. The correction helped push the British and then American programs toward treating an actual deliverable weapon as achievable within years rather than a distant theoretical possibility.
