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Los Alamos

On October 9, 1941, two months before the United States entered World War II, President Franklin D. Roosevelt approved a crash program to develop an atomic bomb. Ernest Lawrence brought Oppenheimer into the Manhattan Project on October 21. Oppenheimer was assigned to take over the project's specific bomb-design research by Arthur Compton at the Metallurgical Laboratory. On May 18, 1942, National Defense Research Committee Chairman James B. Conant, who had been one of Oppenheimer's lecturers at Harvard, asked Oppenheimer to take over work on fast neutron calculations, a task Oppenheimer threw himself into with full vigor. He was given the title "Coordinator of Rapid Rupture"; "rapid rupture" is a technical term that refers to the propagation of a fast neutron chain reaction in an atomic bomb. One of his first acts was to host a summer school for atomic bomb theory in Berkeley. The mix of European physicists and his own students—a group including Serber, Emil Konopinski, Felix Bloch, Hans Bethe, and Edward Teller—kept themselves busy by calculating what needed to be done, and in what order, to make the bomb.

In June 1942, the U.S. Army established the Manhattan Engineer District to handle its part in the atom bomb project, beginning the process of transferring responsibility from the Office of Scientific Research and Development to the military. In September, Brigadier General Leslie R. Groves Jr., was appointed director of what became known as the Manhattan Project. By October 12, 1942, Groves and Oppenheimer had decided that for security and cohesion, they needed to establish a centralized, secret research laboratory in a remote location.

Groves selected Oppenheimer to head the project's secret weapons laboratory, although it is not known precisely when. This decision surprised many, because Oppenheimer had left-wing political views and no record as a leader of large projects. Groves worried that because Oppenheimer did not have a Nobel Prize, he might not have had the prestige to direct fellow scientists, but Groves was impressed by Oppenheimer's singular grasp of the practical aspects of the project and by the breadth of his knowledge. As a military engineer, Groves knew that this would be vital in an interdisciplinary project that would involve not just physics but also chemistry, metallurgy, ordnance, and engineering. Groves also detected in Oppenheimer something that many others did not, an "overweening ambition", which Groves reckoned would supply the drive necessary to push the project to a successful conclusion. Oppenheimer's past associations were not overlooked, but on July 20, 1943, Groves directed that he receive a security clearance " without delay irrespective of the information which you have concerning Mr Oppenheimer. He is absolutely essential to the project." Rabi considered Oppenheimer's appointment "a real stroke of genius on the part of General Groves, who was not generally considered to be a genius".

Oppenheimer favored a location for the laboratory in New Mexico, not far from his ranch. On November 16, 1942, he, Groves and others toured a prospective site. Oppenheimer feared that the high cliffs surrounding it would feel claustrophobic, and there was concern about possible flooding. He then suggested a site he knew well: a flat mesa near Santa Fe, New Mexico, which was the site of a private boys' school, the Los Alamos Ranch School. The engineers were concerned about the poor access road and the water supply but otherwise felt that it was ideal. The Los Alamos Laboratory was built on the site of the school, taking over some of its buildings, while many new buildings were erected in great haste. At the laboratory, Oppenheimer assembled a group of the top physicists of the time, whom he called the "luminaries".

Los Alamos was initially supposed to be a military laboratory, and Oppenheimer and other researchers were to be commissioned into the Army. He went so far as to order himself a lieutenant colonel's uniform and take the Army physical test, which he failed. Army doctors considered him underweight at 128 pounds (58 kg), diagnosed his chronic cough as tuberculosis, and were concerned about his chronic lumbosacral joint pain. The plan to commission scientists fell through when Rabi and Robert Bacher balked at the idea. Conant, Groves, and Oppenheimer devised a compromise whereby the University of California operated the laboratory under contract to the War Department. It soon turned out that Oppenheimer had hugely underestimated the magnitude of the project: Los Alamos grew from a few hundred people in 1943 to over 6,000 in 1945.

Oppenheimer at first had difficulty with the organizational division of large groups but rapidly learned the art of large-scale administration after he took up permanent residence at Los Alamos. He was noted for his mastery of all scientific aspects of the project and for his efforts to control the inevitable cultural conflicts between scientists and the military. Victor Weisskopf wrote:

Oppenheimer directed these studies, theoretical and experimental, in the real sense of the words. Here his uncanny speed in grasping the main points of any subject was a decisive factor; he could acquaint himself with the essential details of every part of the work.

He did not direct from the head office. He was intellectually and physically present at each decisive step. He was present in the laboratory or in the seminar rooms, when a new effect was measured, when a new idea was conceived. It was not that he contributed so many ideas or suggestions; he did so sometimes, but his main influence came from something else. It was his continuous and intense presence, which produced a sense of direct participation in all of us; it created that unique atmosphere of enthusiasm and challenge that pervaded the place throughout its time.