Fact File : Hiroshima and Nagasaki
6 and 9 August 1945
On the morning of 6 August 1945 an American B-29 bomber, the 'Enola Gay', dropped the first atomic bomb used in warfare on the Japanese city of Hiroshima.
The bomb was dropped by parachute and exploded 580m (1,900ft) 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.
On the morning of 9 August, the Americans dropped a second, bigger atomic bomb. 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.
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.'
On 14 August, Japan agreed to the Allies' terms of surrender. At midday on the following day, Emperor Hirohito broadcast the news to the Japanese people. It was the first time his voice had been heard on the radio.
After the war, Hiroshima was rebuilt as a peace memorial city and the closest surviving building to the epicentre was designated the Hiroshima Peace Memorial.
The fact files in this timeline were commissioned by the BBC in June 2003 and September 2005. Find out more about the authors who wrote them.