The following is a timeline of confirmed nuclear weapons explosions.
Much of the history of nuclear weapons still remains classified.
According to the Federation of American Scientists, as of 2025 there were approximately 12,331 nuclear warheads globally, with around 9,604 in military stockpiles, and 3,904 deployed with operational forces. Roughly 2,100 warheads are currently on high alert, ready for use on short notice, primarily by the United States, Russia, United Kingdom, and France.
July 16, 1945: The Trinity test
The Trinity test near Socorro, New Mexico, was the first-ever test of a nuclear weapon (yield of around 20 kilotons).
August 6, 1945: The United States drops an atomic bomb on Hiroshima, Japan (60,000-80,000 immediate deaths, 135,000+ deaths by the end of 1945)
The nuclear weapon (nicknamed ‘Little Boy’) dropped from a United States Army Air Force Boeing B-29 Superfortress bomber (the ‘Enola Gay’) and detonated over Hiroshima, Japan with an energy yield equivalent to that of 15,000 tons of TNT.
The first atomic bomb ever used in warfare was dropped by parachute and exploded 580m (1,900 ft) above the ground. Between 60,000 and 80,000 people were killed instantly. The heat from the bomb was so intense that some people simply vanished in the explosion. Many more died of the long-term effects of radiation sickness. The final death toll was calculated at 135,000. As well as residents of Hiroshima, the victims included Koreans who had been forced to come to Japan as labourers, and American prisoners-of-war who were imprisoned in Hiroshima.
The blast destroyed more than ten square kilometres (six square miles) of the city. And the intense heat of the explosion then created many fires, which consumed Hiroshima and lasted for three days, trapping and killing many of the survivors of the initial blast. Thousands of people were made homeless and fled the devastated city.
Hiroshima was chosen because it had not been targeted during the US Air Force’s conventional bombing raids on Japan, and was therefore regarded as being a suitable place to test the effects of an atomic bomb. It was also an important military base. The Allies feared that any conventional attempt to invade the Japanese home islands would result in enormous casualties, and the bomb was seen as a way of bringing the war against Japan to a swift conclusion. In addition, it may also have been a way of demonstrating American military superiority over the Soviet Union.
August 9, 1945: The United States drops an atomic bomb on Nagasaki, Japan (40,000 immediate deaths, 50,000-80,000+ deaths by the end of 1945)
The nuclear weapon (nicknamed ‘Fat Man’) dropped from a United States Army Air Force Boeing B-29 Superfortress bomber (the ‘Bockscar’) and detonated over Nagasaki, Japan with an energy yield equivalent to that of 21,000 tons of TNT.
The original target was Kokura, but this was obscured by cloud so the bomb was dropped on nearby Nagasaki, an important port. About 40,000 people were killed instantly and a third of the city was destroyed. The final death toll was calculated as at least 50,000. Some sources report death tolls as high as 80,000 by the end of 1945.
Among those in the plane that dropped the bomb on Nagasaki was the British pilot Leonard Cheshire. He later recalled the cloud caused by the atomic blast in Martin Gilbert’s Second World War:
‘Obscene in its greedy clawing at the earth, swelling as if with its regurgitation of all the life that it had consumed.’
July 1946: Operation Crossroads
The Operation Crossroads series in July 1946, at Bikini Atoll in the Marshall Islands, was the first postwar test series and one of the largest military operations in U.S. history.