Nuclear Weapons Archives

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Thermonuclear explosion at Bikini Atoll, March 1954. The unexpected spread of fallout from the test led to awareness of, and research into, radioactive pollution.

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Atomic Bomb History

Nuclear Bombs and Hydrogen Bombs A discovery by nuclear physicists in a laboratory in Berlin, Germany, in 1938 made the first atomic bomb possible, after Otto Hahn, Lise Meitner and Fritz Strassman discovered nuclear fission. In nuclear fission, the nucleus of an atom of radioactive material splits into two or more smaller nuclei, which causes […]

Manhattan Project

America Declares War The agencies leading up to the Manhattan Project were first formed in 1939 by President Franklin D. Roosevelt after U.S. intelligence operatives reported that scientists working for Adolf Hitler were already working on a nuclear weapon. At first, Roosevelt set up the Advisory Committee on Uranium, a team of scientists and military […]

Image labeled '4.0 Sec' of the first Nuclear Test, codenamed 'Trinity', conducted by Los Alamos National Laboratory at Alamogordo, New Mexico circa 1945. (Photo by Fotosearch/Getty Images).

The Trinity Test

The Manhattan Project Beginning in 1939, some American scientists–many of them refugees of fascist regimes in Europe–advocated the development of ways to use nuclear fission for military purposes. By late 1941, the federal government’s Office of Scientific Research and Development, headed by scientist Vannavar Bush, took control of the project. After the United States entered […]

Bombing of Hiroshima and Nagasaki

The Manhattan Project Even before the outbreak of war in 1939, a group of American scientists—many of them refugees from fascist regimes in Europe—became concerned with nuclear weapons research being conducted in Nazi Germany. In 1940, the U.S. government began funding its own atomic weapons development program, which came under the joint responsibility of the […]