2:45am (Tokyo time): The bomber takes off.
The B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets, takes off from Tinian Island, near Guam, carrying the atomic bomb Little Boy.
It will be the first nuclear weapon used in war, and only the second to be detonated in history. The first had been tested two months before, in New Mexico.
3:15am: The bomb is armed.
Enola Gay's weaponeer, Captain William S Parsons, arms Little Boy by adding the explosive charges to the firing mechanism. He had worried that if the bomb was armed and Enola Gay had crashed on takeoff, it might have exploded and killed Americans.
7:09am: The air-raid siren goes off in Hiroshima.
An American aircraft is spotted in the skies above the city. It's a weather plane, which flies over the city most days.
At 7:31am, the all-clear is sounded, and the people of the city go about their day.
8:09am: Enola Gay is spotted.
Japanese spotters notice the bomber heading for Hiroshima. The message is relayed to a local military headquarters: "Three large enemy aircraft are moving west over Saijo (City of Higashi Hiroshima)."
No further alarm is sounded, so very few people are in bomb shelters when the bomb goes off. Instead, they are mostly on their way to work – it's a Monday morning – and are concentrated in the centre of the city.
8:15am: Little Boy is dropped over Hiroshima.
After dropping the bomb, Enola Gay has to turn hard to avoid being overhead as Little Boy explodes. Tibbets says in an interview many years later that he knew he had 42 seconds to turn the huge plane around 159 degrees: "I practised turning, steeper, steeper, steeper, and I got it where I could pull it round in 40 seconds. The tail was shaking dramatically and I was afraid of it breaking off, but I didn't quit. That was my goal. And I practised and practised until, without even thinking about it, I could do it in between 40 and 42, all the time."
On the day, he manages it, and Enola Gay gets clear of the blast.
8:15:44am: the bomb detonates.
Little Boy was meant to explode 600 metres over a bridge, but crosswinds mean that it misses by 250 metres and detonates directly over a surgical clinic.
Within one 10,000th of a second it becomes a fireball 30 metres across and several million degrees centigrade. The fireball expands to nearly 400 metres, cooling to 6,000°C. A blinding flash of white light is followed by a huge shockwave.
Paper instantly bursts into flame as far as 2km away. Between the blast and the flash burns, 90% of people within 500 metres or so of the blast zone are killed. Almost every building within 1.6km is immediately destroyed.
Outside the Bank of Hiroshima, a "human shadow etched in stone" is left on the steps where a woman was sitting.
Shinji Mikamo, 19 at the time, described the moment like this:
"Suddenly I was facing a gigantic fireball. It was at least five times bigger and 10 times brighter than the sun. It was hurtling directly towards me, a powerful flame that was a remarkable pale yellow, almost the colour of white.
"The deafening noise came next. I was surrounded by the loudest thunder I had ever heard. It was the sound of the universe exploding. In that instant, I felt a searing pain that spread through my entire body. It was as if a bucket of boiling water had been dumped over my body and scoured my skin."
Akihiro Takahasha, a 14-year-old schoolboy on the day of the blast, threw himself in the river to assuage the pain of his burning body:
"The heat was tremendous. And I felt like my body was burning all over. For my burning body the cold water of the river was as precious as the treasure. Then I left the river, and I walked along the railroad tracks in the direction of my home. On the way, I ran into an another friend of mine, Tokujiro Hatta. I wondered why the soles of his feet were badly burnt. It was unthinkable to get burned there. But it was undeniable fact the soles were peeling and red muscle was exposed.
"Even I myself was terribly burnt, I could not go home ignoring him. I made him crawl using his arms and knees. Next, I made him stand on his heels and I supported him. We walked heading toward my home repeating the two methods.
"When we were resting because we were so exhausted, I found my grandfather's brother and his wife, in other words, great uncle and great aunt, coming toward us. That was quite coincidence. As you know, we have a proverb about meeting Buddha in Hell. My encounter with my relatives at that time was just like that. They seem to be the Buddha to me wandering in the living hell."
Tomoko Matsumoto, a high school student, remembers:
"When I took a sip of water at the fountain in the school ground I saw a flash. I felt something hot run through my body. The hair of a classmate who was nearby caught fire, and my hair and trousers also caught fire."
In the air above, Tibbets is desperately trying to get his aircraft out of the way of the blast:
"The shockwave was coming up at us after we turned. And the tailgunner said: 'Here it comes.' About the time he said that, we got this kick in the ass. I had accelerometers installed in all airplanes to record the magnitude of the bomb. It hit us with two and a half G. Next day, when we got figures from the scientists on what they had learned from all the things, they said: 'When that bomb exploded, your airplane was 10 and half miles away from it...'
"The Hiroshima bomb did not make a mushroom. It was what I call a stringer. It just came up. It was black as hell, and it had light and colours and white in it and grey colour in it and the top was like a folded-up Christmas tree … I think it's best stated by one of the historians, who said: 'In one microsecond, the city of Hiroshima didn't exist.'"
8:30am: The first report gets out of Hiroshima to the rest of Japan.
A 14-year-old schoolgirl, Yoshie Oka, working for military communications, gets a message to local military headquarters: "Hiroshima has been attacked by a new type of bomb. The city is in a state of near-total destruction."
8:45am: The firestorm begins.
The blast has started fires all over the centre of the city. The fires create great winds, spreading the flames further and creating a firestorm.
The secret US Strategic Bombing Survey recorded the events like this:
"Only directly exposed surfaces were flash burned. Measured from GZ [ground zero], flash burns on wood poles were observed at 13,000 feet, granite was roughened or spalled by heat at 1,300 feet, and vitreous tiles on roofs were blistered at 4,000 feet ... six persons who had been in reinforced-concrete buildings within 3,200 feet of air zero stated that black cotton blackout curtains were ignited by radiant heat ... dark clothing was scorched and, in some cases, reported to have burst into flame from flash heat ... but a large proportion of over 1,000 persons questioned was in agreement that a great majority of the original fires was started by debris falling on kitchen charcoal fires, by industrial process fires, or by electric short circuits."
Akiko Takakura, a 20-year-old who miraculously survived despite being just 300 metres from the blast, described the fires like this:
"Many people on the street were killed almost instantly. The fingertips of those dead bodies caught fire and the fire gradually spread over their entire bodies from their fingers. A light-grey liquid dripped down their hands, scorching their fingers. I, I was so shocked to know that fingers and bodies could be burned and deformed like that. I just couldn't believe it. It was horrible. And looking at it, it was more than painful for me to think how the fingers were burned, hands and fingers that would hold babies or turn pages, they just, they just burned away.
"For a few years after the A-bomb was dropped, I was terribly afraid of fire. I wasn't even able to get close to fire because all my senses remembered how fearful and horrible the fire was, how hot the blaze was, and how hard it was to breathe the hot air. It was really hard to breathe. Maybe because the fire burned all the oxygen, I don't know. I could not open my eyes enough because of the smoke, which was everywhere. Not only me but everyone felt the same. And my parts were covered with holes [Takakura sustained 100 wounds on her back]."
8:50am: The first burns casualties are brought to the Army Marine Regiment Headquarters in Ujina.
9:00am: A black rain filled with radioactive ash starts to fall over the city.
It reaches as far as 30km away from the explosion. "The United States is spraying oil and trying to burn us. Evacuate to an air-defense shelter," a colleague tells factory worker Akio Kawano.
10am: The firestorm reaches its peak, and burns ferociously for another four or five hours.
The Strategic Bombing Survey records: "The fire wind seems to have reached its maximum velocity about 2 to 3 hours after the bomb explosion, following which it began to diminish in intensity. ... the heavier rain began about 3,500 feet west of GZ and extended westward about 5,000 feet. Light rain was reported to have fallen near the center of the city. ... Rain fell almost exclusively in the northwest area of the city ... accounted for by the light natural wind from the southeast which blew particles of hot carbon northwestward to a cooler area where moisture condensed about them and fell as rain."
According to one eyewitness, Father John Siemes, it is 30 hours before effective firefighting or rescue teams arrive, because the city's emergency services have been largely destroyed. By the time the firestorm dies down, at least 70,000 people are dead.
1:58pm: Enola Gay lands at its airfield on Tinian Island.
After dropping the bomb, its flight home was uneventful, apart from one sighting of a Japanese fighter in the distance. Captain Robert Lewis, the plane's co-pilot, says years later of the experience: "We dropped in, and then we flew away as fast as we could go. I looked back and saw the mushroom cloud forming. I saw the whole city being destroyed and I wrote in my log: 'Oh, God. What have we done.'"
Tibbets's response is different: "I had no problem with it. I knew we did the right thing because when I knew we'd be doing that I thought, yes, we're going to kill a lot of people, but by God we're going to save a lot of lives. We won't have to invade [Japan]."
5pm: Military hospitals and relief medical centres start dealing with the huge numbers of wounded.
The bomb exploded near two large hospitals and killed 90% of the doctors in the city, so surviving medical staff are under huge pressure. There are 18 such relief medical centres designated around the city. The wounded are in a terrible state. "The streets were like a scene from hell. The faces of staggering girl students were burnt beyond recognition. Their skin was peeling and hanging down. When I saw them, I could not remain on my feet. I just sat down for a while," said one witness, Kuniyoshi Aikawa.
Father John Siemes, a German Jesuit priest working in the city, remembers:
"Iodine is applied to the wounds but they are left uncleansed. Neither ointment nor other therapeutic agents are available. Those that have been brought in are laid on the floor and no one can give them any further care. What could one do when all means are lacking?
"Among the passers-by, there are many who are uninjured. In a purposeless, insensate manner, distraught by the magnitude of the disaster, most of them rush by and none conceives the thought of organising help on his own initiative. They are concerned only with the welfare of their own families – in the official aid stations and hospitals, a good third or half of those that had been brought in died. They lay about there almost without care, and a very high percentage succumbed. Everything was lacking, doctors, assistants, dressings, drugs, etc."
At some point in the afternoon, Rokuro Kubosaki, a Hiroshima resident, sees two American prisoners of war, apparently dead, shackled to a telegraph pole:
"They appeared to be dead. I was so overwhelmed with hatred that I threw a glass bottle at them. It wasn't those prisoners that dropped the bomb. I regret what I did."
There were no POW camps in Hiroshima, but 12 prisoners were being held in a local military police station. Most of them died immediately; two may have been executed by their captors, and two were apparently stoned to death by furious crowds. Masaharu Kuritani saw "a young American soldier" still breathing: "His hands were tied up. He was wearing a big blue stone ring on one of his fingers. Several hours later he was dead. I saw many rocks and tiles around him."
Torao Orimoto, a naval aviation factory worker, remembers:
"There were two American soldiers on the ground near the Chugoku Military Police Headquarters. One of them may have been dead. We were ordered to carry the one who was conscious on a stretcher.
"On the way, I heard the soldier groan 'water', so I poured water from a canteen on his face. We tied him up to a telephone pole with a metal wire. An old woman kicked him, saying, 'You killed my son.'"
Midnight (11am, 6 August, US time): President Truman announces that a new kind of weapon has been dropped on Japan.
"Sixteen hours ago an American airplane dropped one bomb on Hiroshima and destroyed its usefulness to the enemy. That bomb had more power than 20,000 tons of TNT. It had more than two thousand times the blast power of the British 'Grand Slam' which is the largest bomb ever yet used in the history of warfare.
"The Japanese began the war from the air at Pearl Harbor. They have been repaid manyfold. And the end is not yet. With this bomb we have now added a new and revolutionary increase in destruction to supplement the growing power of our armed forces. In their present form these bombs are now in production and even more powerful forms are in development.
"It is an atomic bomb. It is a harnessing of the basic power of the universe. The force from which the sun draws its power has been loosed against those who brought war to the Far East…
"We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city. We shall destroy their docks, their factories, and their communications. Let there be no mistake; we shall completely destroy Japan's power to make war."
9 August: A second bomb is dropped on Nagasaki.
One man, Tsutomu Yamaguchi, had fled Hiroshima, where he worked in a shipbuilding factory, after the bombing. He made his way to his hometown, Nagasaki, just in time for the blast there. He survived both, and died in 2010, aged 93. "My double radiation exposure is now an official government record. It can tell the younger generation the horrifying history of the atomic bombings even after I die," he told a Japanese newspaper in 2009.
According to Tibbets, a third bomb was ready to be deployed if Japan had not surrendered:
"Unknown to anybody else – I knew it, but nobody else knew – there was a third one. See, the first bomb went off and they didn't hear anything out of the Japanese for two or three days. The second bomb was dropped and again they were silent for another couple of days.
"Then I got a phone call from General Curtis LeMay [chief of staff of the strategic air forces in the Pacific]. He said, 'You got another one of those damn things?' I said, 'Yessir.' He said, 'Where is it?' I said, 'Over in Utah.' He said, 'Get it out here. You and your crew are going to fly it.' I said, 'Yessir.'
"I sent word back and the crew loaded it on an airplane and we headed back to bring it right on out to Tinian and when they got it to California debarkation point, the war was over."
Tibbets says that no one knows what the target would have been.
15 August: The Japanese emperor surrenders. In a speech to the nation, delivered by radio – the first time the people of Japan had heard their emperor’s voice – he says:
"The enemy … has begun to employ a new, most cruel bomb, the power which to do damage is indeed incalculable, taking toll of many innocent lives. Should we continue to fight, it would only result in the ultimate collapse and obliteration of the Japanese nation ... but would lead also to the total extinction of human civilization. Such being the case, how are we to save millions of our subjects, or ourselves, to atone before the hallowed spirits of our Imperial ancestors? This is the reason we have ordered the acceptance of the provisions of the joint declaration of the Powers."
1946 and the years that follow: The real aftermath starts to become apparent.
The total number of deaths from Hiroshima will never be known, but as many as 100,000 people may have died from radiation-related cancers in the years that followed, and many children were born with birth defects. Kunizo Hatanaka's wife gave birth in February 1946, having been exposed to the radiation of the bomb while pregnant. Their daughter Yuriko was born with microcephaly, a developmental disorder in which the brain and skull are too small. When Yuriko was 11, with a severe learning disability, her parents learned that this was a result of the bomb.
More tragedy followed for the family, which Kunizo believes was also related to the bomb: "Some years later, my wife began to suffer an ache in her waist and legs and went to the doctor. He encouraged her to take a thorough examination. Meanwhile, my wife's knees became weaker and weaker. Finally it turned out that she had developed bone cancer. Her condition continued to become worse and one day, December 26, 1978, she passed away and never came back. She died very silently."
Others bear the scars of the blast for the rest of their lives. Nakayama Shiro, a survivor, wrote:
"I hated for people to stare at me. … Yet, every nerve in my body was attuned to the outside world; and to avoid even the slightest sinister look, I walked with a rigid on-guard posture. … Even so, I secluded myself at home and spent hours before the mirror, looking at my own face. What I saw was ugly hunks of flesh, like lava oozing from a crater wall, covering the left half of my face."