(Stafford L. Warren, M.D. The Role of Radiology in the Development of the Atomic Bomb)
The atomic bomb was first detonated at Alamogordo, New Mexico, on 16 July 1946, dropped for military purposes on Hiroshima, Japan on 6 August 1945, and at Nagasaki 3 days later.
At the conference on Theoretical Physics held in Washington, D.C. 26, January 1939, which was attended by most of the principal workers in this field, reports were made on the word done on the fission of unranium by Otto Hahn, Fritz Srassman, Otto R. Frisch, and Lise Meitner.
By June 1940, 18 months later, the principal facts about fission of the atom had been discovered and were known to the scientific world...Meantime, because of their military implications, these developments had been brought to the attention of President Franklin D. Roosevelt, in the fall of 1939, largely on the insistence of Dr. Albert Einstein.
By June 1940, it was known that fission was produced by thermal neutrons in U-235, the rare isotope of uranium. It was not yet known that it was also produced in U-238, the more common isotope. Six months later, active work in the field of fission was underway in 10 or more universities, as well as at the Carnegie Institution of Washington, the Standard Oil Development Co., and the National Bureau of Standards. The year 1941 was highly critical. Results from various investigations confirmed more surely the important military implications of uranium fission, the work on which was expanded at a very rapid rate. At the request of Dr. Bush and Dr. Conant, several special reports were made by the National Academy of Sciences. When British scientists reported that a U-235 bomb of great power was feasible, Dr. Urey and George B . Pegram, Ph.D., from Columbia University were sent to England for firsthand discussions.
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