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The mushroom cloud of the atomic bombing of Nagasaki, Japan on August 9, 1945 rose some 18 kilometers (11 miles) above the bomb's hypocenter. |Nuclear weapons |
|Arms race |
|Civil defense |
|Anti-nuclear opposition |
|Nuclear-armed states |
|United States. Russia |
|United Kingdom. France |
|China. India. Israel |
|Pakistan. North Korea |
|South Africa (former). |
|This box: view · talk · edit |
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission andfusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission ("atomic") bomb test released the same amount of energy as approximately 20,000 tons of TNT. The first thermonuclear ("hydrogen") bomb test released the same amount of energy as approximately 10,000,000 tons of TNT.
A modern thermonuclear weapon weighing little more than a thousand kilograms (2,200 pounds) can produce an explosion comparable to the detonation of more than a billion kilograms (2.2 billion pounds) of conventional high explosive. Thus, even single small nuclear devices no larger than traditional bombs can devastate an entire city by blast, fire and radiation. Nuclear weapons are considered weapons of mass destruction, and their use and control has been a major focus of international relations policy since their debut.
In the history of warfare, only two nuclear weapons have been detonated offensively, both near the end of World War II. The first was detonated on the morning of 6 August 1945, when the United States dropped a uranium gun-type device code-named "Little Boy" on the Japanese city ofHiroshima. The second was detonated three days later when the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki, Japan. These two bombings resulted in the deaths of approximately 200,000 Japanese people (mostly civilians) from acute injuries sustained from the explosion. The role of the bombings in Japan's surrender and the U.S.'s ethical justification for themremains the subject of scholarly and popular debate.
Since the Hiroshima and Nagasaki bombings, nuclear weapons have been detonated on over two thousand occasions for testing purposes and demonstration purposes. A few states have possessed such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and that acknowledge possessing such weapons—are (chronologically) the United States, the Soviet Union(succeeded as a nuclear power by Russia), the United Kingdom, France, the People's Republic of China, India, Pakistan, and North Korea.Israel is also widely believed to possess nuclear weapons, though it does not acknowledge having them.
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|1 Types of nuclear weapons |
|2 Weapons delivery |
|3 Nuclear strategy |
|4 Governance, control, and law |
|4.1 Disarmament |
|5 Anti-nuclear weapons movement |
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