At 8:15am on 6 August 1945, a nuclear bomb nicknamed "Little Boy" was dropped on Hiroshima by an American B-29 Superfortress bomber, the Enola Gay, flown by Colonel Paul Tibbets.
The blast and subsequent fire devastated an area of five square miles (13 square kilometres). More than 60% of the city's buildings were completely destroyed.
An estimated 80,000 people died immediately, but injuries and radiation took the final death toll to around 140,000 from Hiroshima's population of 350,000.
Three days later, a larger bomb nicknamed "Fat Man" was dropped on the city of Nagasaki. Japan surrendered, ending the Second World War.