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Joe 1, the first Soviet atomic test, August 29, 1949.NUCLEAR PROLIFERATION
Events > Postscript -- The Nuclear Age, 1945-Present

Even before the atomic bombing of Hiroshima, many of the scientists of the Manhattan Project were arguing that international control of atomic energy was essential.  Any modern, industrialized state, they reasoned, could eventually build its own atomic bomb if it so chose.  There was no "secret" scientific theory or principle concerning the bomb.   Its possibility was fundamental to modern physics.  Then as now, the primary difficulties were engineering related: separating uranium-235 or producing plutonium and designing and building the actual weapon. 

To date eight nations have openly conducted nuclear tests.  They are: 

RDS-37, first Soviet hydrogen bomb test, November 22, 1955The second nation to test an atomic bomb was the United States's Cold War rival, the Soviet Union.  This development was not unexpected, but the timing was.  The American intelligence community generally believed the Soviet Union would not have "the bomb" until 1952 or even later, not August 1949.  Soviet wartime espionage sped its weapons development, but probably only by a year or two.  (The bomb tested on August 29, 1949, closely resembled the implosion device developed at Los Alamos.)  In August 1953, the Soviet Union tested its first "boosted fission" bomb, which used fusion to increase its yield, and in November 1955 the Soviet Union produced its first "true" thermonuclear explosion (left).  

Hurricane, first British test, October 3, 1952In 1952, Britain became the next nation to join the "nuclear club."  This was not surprising, as the Manhattan Project had essentially been a joint Anglo-American program, especially once the British Mission of scientists arrived at Los Alamos in 1943 and 1944.  The Atomic Energy Act of 1946 prohibited the United States from assisting the post-war British nuclear weapons program, but within six years Britain was able to successfully perform a nuclear test.  At midnight on October 3, 1952, off the Australian island of Trimouille, a 25 kiloton nuclear weapon was detonated inside the hull of a British frigate, H.M.S. Plym.  The test was codenamed "Hurricane" (right).  On November 8, 1957, Britain conducted its first fully successful thermonuclear test, "Grapple X/Round C."  

596, first Chinese test, October 16, 1964France and China joined the nuclear club in the 1960s.  The first French nuclear explosion, "Gerboise Bleue," was an unusually large first test: 60-70 kilotons.  It was detonated at Reggane, Algeria, on February 13, 1960.  France tested a thermonuclear weapon on the Pacific atoll of Fangatuafa on August 24, 1968.  The first Chinese atomic test (left), codenamed "596," took place at the Lop Nor Testing Ground on October 16, 1964.  (The leader of China, Mao Zedong, had famously declared that nuclear weapons, and by extension the United States, were a "paper tiger," but that did not prevent him from pushing the Chinese nuclear program through to fruition.)  Only three years later, on June 17, 1967, China conducted its first thermonuclear test.  

On July 1, 1968, the Nuclear Non-Proliferation Treaty was signed by the United States, Great Britain, the Soviet Union, and 59 other nations.  The purpose of the treaty was to prevent the acquisition of nuclear weapons by any nation that did not already possess them. The treaty took effect in March 1970, and in 1992 China and France joined as well.  As of 2000, only Cuba, Israel, India, and Pakistan had not signed the Non-Proliferation Treaty.  

Crater left from underground Indian test, May 18, 1974The nuclear weapons programs of the original five nuclear powers were driven primarily by Cold War concerns.  In the 1970s, however, a largely-unrelated arms race in South Asia produced two more members of the nuclear club: India and Pakistan.  India conducted its first atomic test, "Smiling Buddha," on May 18, 1974 (right).  (The test was conducted underground.)  In the 1980s reports began to emerge that, although it had not yet conducted a nuclear test, Pakistan possessed nuclear weapons as well.  In May 1998, as retaliation for a new series of Indian nuclear tests the previous month, Pakistan conducted several tests of its own.

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Sources and notes for this page.

The text for this page is original to the Department of Energy's Office of History and Heritage Resources.  The information on the Nuclear Non-Proliferation Treaty is from the Federation of American Scientists (FAS) web page of the same title, which is available at  Other information for this entry was derived from the country-specific pages on The Nuclear Weapon Archive web site, available at, and the country-specific web pages from the FAS site, the "Nuclear Forces Guide," available at  Photographs are courtesy the Federation of American Scientists.

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