Photo Of Nuclear Explosion

In 1963, the United States, Soviet Union, and United Kingdom signed the Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. The treaty permitted underground tests. Many other non-nuclear nations acceded to the Treaty following its entry into force; however, three nuclear weapons states have not acceded: France, China, and North Korea.
In the history of warfare, two nuclear weapons have been detonated — both by the United States, during the closing days of World War II. The first event occurred 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 of Hiroshima. The second event occurred three days later when, again, the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki. These bombings resulted in the immediate deaths of around 120,000 people and more over time, because of the nuclear radiation. The use of these weapons was and remains controversial.