ORIGINS OF THE PROJECT
Our story begins in the year 1938, when two German chemists, Otto Hahn and Fritz Strassmann, discovered nuclear fission. Nuclear fission occurs when a neutron slams into a larger atom, forcing it to excite and split into two smaller atoms—also known as fission products. Additional neutrons are also released that can initiate a chain reaction, and when each atom splits, a tremendous amount of energy is released. This discovery, along its theoretical explanation by Lise Meitner and Otto Frisch made the development of an atomic bomb a theoretical possibility.
With the start of World War II a year later, some started to worry that the Germans would be able to create the first atomic bomb, which would essentially make the war unwinnable for the Allies. In August of 1939, two Hungarian-born physicists, Leo Szilard and Eugene Wigner drafted the Einstein-Szilard letter. Signed by Albert Einstein himself, this letter warned President Franklin D. Roosevelt of the potential development of "extremely powerful bombs of a new type" by the Germans. This letter urged the United States to act quickly to make sure that they would develop such weapon first.
The US started to take all steps necessary to get large quantities of uranium ore, which is needed for the production of an atomic bomb. They also accelerated scientific research in the area of nuclear chain reaction, especially Enrico Fermi's research.
Roosevelt gave the task of investigating the issues raised in the letter to a physician by the name Lyman Briggs of the National Bureau of Standards. A special group called The Advisory Committee on Uranium was set up to research Uranium's potential. This committee held a meeting on the 21st of October, 1939, which was attended by Szilard and Wigner themselves, as well as by the theoretical physicist Edward Teller. After the meeting, the committee would report back to Roosevelt with their conclusion that uranium "would provide a possible source of bombs with a destructiveness vastly greater than anything now known."
In 1940, Columbia University was funded $6,000 by the government in for research in the area of nuclear chain reactions. Soon enough, a team of Columbia professors including Fermi and Szilard and well as the physicists Eugene T. Booth and John Dunning successfully created the first nuclear fission reaction in America, which verified the work of Hahn and Strassmann. The same team would soon build a series of prototype nuclear reactors in Pupin Hall at Columbia, however they were not yet able to achieve the desired chain reaction.
The Advisory Committee on Uranium became the National Defence Research Committee (NDRC) on Uranium when that organization was formed on the 27th of June, 1940. It was proposed by Briggs to spend $167,000 on research of uranium, especially the Uranium-235 isotope (which, unlike usual uranium, can sustain the desired nuclear chain reaction) as well as plutonium (a radioactive chemical) which was discovered earlier that year.
On June 28th of 1941, Roosevelt signed Executive Order 8807, which created the Office of Scientific Research and Development (OSRD), with Vannevar Bush as its director. The purpose of this office was to partake in large engineering projects as well as research. The NDRC Committee on Uranium ended up becoming the S-1 Section of the OSRD, so they were now called S-1 Executive Committee. The word "uranium" was dropped out of the name for security reasons.
In the meantime, in Britain, Otto Frisch and Rudolf Pierls at the University of Birmingham made an important breakthrough in their research on the critical mass (the smallest amount of fissile material needed for a sustained nuclear chain reaction) of Uranium-235 in June of 1939. According to their calculations, it was within 10 kilograms, which was perfect as it was small enough to be carried by a bomber of the day. In March of 1940, the MAUD Committee was formed in Britain with the goal of continuing the works on developing the first atomic bomb. In July of the same year, Britain, being an ally of the United States, offered to give them access to its research in this area. As part of this scientific exchange, the MAUD Committee findings were sent to the United States. One of MAUD's members, the Australian Physicist Mark Oliphant, flew to the United States in August of 1941 and learned that the important data provided by the MAUD Committee did not reach many key American physicists. He was confused as for the reason for this, and met with the nuclear physicist Ernest O. Lawrence to point this issue out. After hearing him out, Lawrence immediately started his own research into Uranium and also ended up involving many important physicists such as James B. Conant, Arthur H. Compton and George B. Pegram. The issue was now resolved, as Oliphant succesfully turned many important physicists' attention on the potential power of an atomic bomb.
On the 9th of October, 1941, President Roosevelt officially approved the atomic bomb program after he discussed this matter with Vannevar Bush along with Vice President Henry A. Wallace. To control the program, he formed a Top Policy Group which consisted of himself, Wallace, Bush, and Conant as well as Secretary of War Henry L. Stimson and the Chief of Staff of the Army General George C. Marshall. Roosevelt chose the Army to run and manage the project rather than the Navy, with the reason being that the Army had more experience with the management of such large-scale construction projects. Additionally, Roosevelt agreed to collaborate with the British on this project, and on the 11th of October of the same year, just two days after approving the whole program, he sent a message to Prime Minister Winston Churchill with his suggestion of the cooperation on the atomic matters.