Sixty years ago the crew of the Enola Gay watched in awe as their payload detonated over Hiroshima.
"As the bomb exploded, we saw the entire city disappear," said co-pilot Captain Robert Lewis. "I wrote in my log: 'My God, what have we done?"
Below, thousands of people were instantlycarbonised in a blast that was thousands of times hotter than the sun's surface; further from the epicentre, birds ignited in mid-flight, eyeballs popped and internal organs were sucked from bodies of victims.
By the end of the day an estimated 160,000 were dead or injured and the bomb's "ghosts" walked the city - thousands of survivors who would die within days, often with the word "mizu" - water - on their lips. Many more subsequently died - and are still dying - from cancers.
US President Harry Truman, who had ordered the destruction of Hiroshima, later said: "We have discovered the most terrible weapon in the history of the world," but steadfastly defended its use.
This March Paul Tibbets, pilot of the Enola Gay, said: "If you give me the same circumstances, hell yeah, I'd do it again."
J. Robert Oppenheimer, the scientist who oversaw the building of the bomb, was more ambiguous. He famously said after the first test detonation: "Now I am become death, the destroyer of worlds."
This weekend Hiroshima will side-step the endless debates and concentrate on commemorating the victims.
