The Manhattan Project was the bland code name given to an effort of unprecedented scope and secrecy to produce the atomic bomb during World War II. It began as a “uranium committee” under Vannevar Bush’s National Research Defense Council and its successor, the Office of Scientific Research and Development (OSRD). Its expansion and secret existence approved personally by President Franklin D. Roosevelt, the Manhattan Project expended nearly $2 billion, a cost about two-thirds that of all the conventional bombs, mines, and grenades procured for the entire war effort, and all without direct knowledge of Congress. The result was a vast complex of “atomic cities” across the nation, where thousands of scientists and engineers worked in extreme secrecy, and which produced two operational bombs used on Hiroshima and Nagasaki in August 1945.
Shortly after the discovery of radioactivity in the 1890s, the possibility of liberating the enormous potential energy within matter motivated much theoretical and laboratory work. The so-called splitting of the atom in an experimental setting, with its implications for moving the weapons concept toward reality, was achieved by German physicists in late 1938, and perhaps in Italy a few years earlier. Leo Szilard, a Hungarian physicist living in New York and in communication with other refugee scientists from Germany and Russia, joined in 1939 with another emigre, Edward Teller, to persuade Albert Einstein to lend his name and influence to a letter informing President Roosevelt of the danger.
British and American physicists then worked on the problem without much progress beyond demonstrating the theoretical possibility of such a weapon. After Pearl Harbor, and believing that the Germans were working effectively toward an atomic bomb, Vannevar Bush and others became convinced that developing an atomic bomb required a massive and organized effort that could produce a workable fission weapon within three years or so. Roosevelt agreed, and in the summer of 1942 the project was established within the U. S. Army Corps of Engineers, where its massive construction projects and funding could be most easily hidden. General Leslie Groves, a brusque organizational genius with graduate degrees in engineering who had just completed building the Pentagon, assumed control of what was termed the Manhattan Engineer District and attempted to maintain strict security within the project.
Leslie Groves (r) and Dr. J. R. Oppenheimer examine an atomic test site, 1945. (New York World Telegram and the Sun Newspaper Collection. Library of Congress)
Six months later, barely a year after Pearl Harbor, a team of physicists directed by the Italian emigre Enrico Fermi, achieved the first sustained and controlled chain reaction with uranium, and construction was underway on several new sites. In Hanford, Washington, a plutonium extraction plant arose; in Oak Ridge, Tennessee, massive facilities were constructed to purify and extract, literally atom by atom, a specific isotope from uranium. Near isolated Los Alamos, New Mexico, thousands of physicists, chemists, and engineers gathered under the leadership of J. Robert Oppenheimer in hastily constructed military facilities to pursue the science and practical engineering of bomb design. At universities and industrial facilities throughout the country, other teams worked on various parts of the problem. Reflecting wartime tensions in Soviet-Ameri-can relations and in the Grand Alliance against the Axis, the British were privy to—and junior partners in— the Manhattan Project, while the Soviets were excluded from participation and knowledge (except through their own espionage).
Both eventual bomb designs were fission weapons— designed to compress purified uranium or plutonium long enough (a split second) for the material to achieve critical mass and the subsequent chain reaction that would release the explosive power. The uranium weapon (“Little Boy”) was relatively unproblematic and did not even need to be tested before its use on Hiroshima in August 1945. The plutonium weapon (“Fat Man”) was used on Nagasaki, and was first tested at Alamogordo, New Mexico, in July 1945.
The atomic scientists, whom Groves called his bunch of “brilliant crackpots,” initially worked together in patriotic unanimity. Deep rifts about the project and the use of the bomb developed after it became clear by 1944 that Germany would not be a contender in this race. Nonetheless, Groves, Oppenheimer, Bush, and others drove the project forward and presented it to a surprised President Truman shortly after Roosevelt’s death in April 1945. The project and its leaders survived congressional and other scrutiny after the war largely because it was deemed a brilliant success that had won the final phase of the war and saved thousands of lives. The physical and personnel infrastructure became elements of an enormous and elaborate new cold war complex, with some of the laboratories under the civilian Atomic Energy Commission and others absorbed into the new Department of Defense.
Further reading: Richard G. Hewlett and Oscar E. Anderson, Jr., A History of the United States Atomic Energy Commission, vol. 1: The New World, 1939-1946 (University Park: Pennsylvania State University Press, 1962); Richard Rhodes, The Making of the Atomic Bomb (New York: Simon & Schuster, 1986).
—Joseph N. Tatarewicz
World History
