An atomic bomb code-named Little Boy dropped by the US B-29 bomber Enola Gay exploded above the centre of Hiroshima at 8:15 am on August 6, 1945.
The bombing of the city 700 kilometres west of Tokyo, in the closing days of World War II, ushered in the nuclear age. It was also the first use of nuclear weapons against human beings.
The 4-ton uranium bomb killed tens of thousands instantly. By the end of the year, a total of about 140,000 people had died from the attack and its after-effects.
Three days later, on August 9, another atom bomb code-named Fat Man released from a B-29 was detonated over the port city of Nagasaki. Around 74,000 people there lost their lives by the end of the year.
The victims of the two bombings included tens of thousands of Koreans, students from China and South-East Asia, and US and Europeans prisoners of war.
The nuclear attacks increased the pressure for Japan to surrender, which it did on August 15, 1945.