Between July 18 and August 15, 1939, one of the most consequential letters in modern history was drafted by Albert Einstein and the Hungarian-born physicist Leo Szilard. The letter, which was eventually delivered to President Franklin Roosevelt,led to the Manhattan Project and the development of the first two atomic weapons.
Szilard and two other Hungarian-born physicists, Edward Teller and Eugene Wigner, had initially contacted Einstein because they were concerned with preventing the Germans from gaining access to uranium ore being mined in the Belgian Congo for their experiments with nuclear fissure. Einstein personally knew the Queen of Belgium and was thought to be the perfect person to draft and sign a letter warning of these dangers. Around the same time, Szilard spoke to economist Alexander Sachs,who was a friend of Roosevelt’s, and suggested Einstein should warn the president as well of the dangers raised by recent breakthroughs in the science of nuclear fission.
Meeting together again on July 30, 1939, Einstein and Szilard began work on the letter for President Roosevelt about developments in the science of nuclear chain reactions and the possibilities opened up by that research.
Einstein and Szilard began the letter by outlining the recent scientific work in this area and the possibilities for immediate development: “In the course of the last four months it has been made probable … that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future.” Einstein wanted to make it clear that the implications of this recent research were not theoretical but held the potential for the development of a weapon in the immediate future.
However, neither Einstein nor Szilard were sure that the process of a nuclear chain reaction could be used to make an easily transportable weapon: “This new phenomenon could lead to the construction of bombs, … However such bombs might very well prove to be too heavy for transportation by air.” The thought was that the bomb might be sent by boat into an enemy port.
The letter had three further purposes. The second was to alert Roosevelt to the fact that the United States did not have good quality uranium ore. The implication was that securing this ore would be key to developing a bomb based on nuclear fission.
The letter then suggested that Roosevelt should designate someone to liaise between the administration and the physicists and academic institutions where the nuclear fission work was occurring. Einstein and Szilard also asked, in a somewhat backhand way, for funding for such research.
Finally the letter warned about developments in Germany,which hinted that the Germans were also involved in similar research and had stopped the sale of uranium ore from Czechoslovakian mines, one of the better sources of uranium ore.
Although the letter was dated August 1939, it was not delivered to Roosevelt until October of that year. Sachs was concerned that the letter might be overlooked or not clearly understood, and he waited until he could secure a meeting with Roosevelt on October 11, 1939, to deliver it. Sachs not only read the letter to Roosevelt but added his own comments and emphasized the possible dangers of this research in German hands. Roosevelt clearly saw the possible implications of this research. By November 1939, an Advisory Committee on Uranium had been established and provided a report recommending the acquisition of uranium oxide and funding of continued experiments. Information received in 1940 from the British bolstered the possibility that this research might lead to a weapon. By the time the United States entered World War II on December 8, 1941, the possibility that a bomb could be built using this research had been confirmed and, in 1942, the Manhattan Project was born.
Last week marked the 75th anniversary of the outcome of the U.S. research on nuclear fission when bombs were dropped over Hiroshima and Nagasaki on August 6 and 9, 1945, in a bid to end World War II. As with many of the scientists who regretted their work, including Szilard and Robert Oppenheimer, Einstein later said that if he had known the Germans would not pursue the nuclear fission work, he would not have recommended the U.S. pursue this research. But history is what was and not what might have been.