At 8.15am on August 6, 1945, ‘Little Boy’ was released from Enola Gay, the B-29 Superfortress captained by Colonel Paul Tibbets Junior.
The first atomic weapon to be used in warfare dropped silently for 43 seconds, with a parachute billowing behind slowing its descent enough to allow Tibbets and his crew to escape the ensuing explosion.
At approximately 1,890feet above the Japanese city of Hiroshima it detonated, unleashing a blinding flash and a force of unprecedented magnitude.
The bomb missed its target by 800 feet, striking above the Shima Surgical Hospital instead of the Aioi Bridge.
The blast obliterated everything within the surrounding square mile. Enola Gay’s crew, now six miles away, were rocked by the shockwave.
Observers aboard Necessary Evil – one of three other B29s in the mission – began recording the aftermath, capturing the white mushroom cloud rising above 45,000 feet.
The immediate reaction aboard the aircrafts was a mix of awe and unease. The usual post-mission levity was absent.
Instead, a subdued silence settled over the crews as they turned back south-eastwards toward base.
Over Hiroshima, chaos had erupted. The temperature at Ground Zero was estimated to be several thousand degrees, approximately the surface temperature of the sun.
The explosion, equal parts fireball and shockwave, levelled buildings, incinerated bodies, and blocked out the sun.
Five square miles of the city centre would be consumed by firestorms. Forty thousand were killed in the blink of an eye.
At least thirty thousand more would succumb to their injuries over the next forty-eight hours.
The mission that was unlike any the world had known had been set in motion from Tinian Island in the Pacific Ocean in the early hours of August 6, 1945.
Colonel Tibbets, leading a group of elite aviators from the 509th Composite Group, had been personally visited by General Curtis LeMay, commander of the XX Bomber Command, who handed him sealed orders: ‘Special Bombing Mission No. 13’.
Hiroshima, a port city in southern Japan, had been chosen because it was deemed a vital urban industrial area and therefore a legitimate military target.
Secondary and tertiary targets were designated as Kokura and Nagasaki.
No friendly aircraft would be allowed within a 50-mile radius of these locations during the strike, ensuring both secrecy and safety.
A safety cordon of U.S. Navy ships and submarines would be positioned towards the Home Islands if the crew should need to ditch in the sea.
Preparations on the base were meticulous and cloaked in strict security. LeMay informed Tibbets that 32 copies of the orders were disseminated across bases in Guam, Iwo Jima, and Tinian.
Little Boy, an enriched uranium-based device, was carefully guarded, with its components kept disarmed to mitigate risk.
Even General LeMay himself was thoroughly searched before the military policeman would allow him to accompany Tibbets to view the ‘gadget’ in the technical area.
Captain William ‘Deak’ Parsons, who had been assigned from the Manhattan Project as Tibbets’ weaponeer, had convinced the ‘Tinian Chiefs’ – the military and scientific leaders on the base – to arm the bomb only after take-off to avoid the risk of accidental detonation on the base’s enormous runway.
With the Enola Gay prepared and painted with Tibbets’s mother’s name on the nose, the 12foot-long bomb was lifted into the aircraft’s belly.
It bore messages from base crews, including one that read, ‘To Emperor Hirohito, from the Boys of the Indianapolis.’
The crew, despite understanding the gravity of their mission from their final briefing that night, struggled with the enormity of what lay ahead.
They were told to get some rest before the operation, but few could sleep. Tibbets himself played cards to pass the time.
He had earlier informed his men that they would be dropping a bomb unlike any other, one capable of unleashing the destructive force of 15,000 tons of TNT.
Two key changes were introduced: the aircraft’s call sign would be altered from ‘Victor’ to ‘Dimples’, and the Enola Gay would fly at a lower altitude at the start of the mission to allow Captain Parsons to arm the bomb safely.
The early morning hours saw a flurry of movement as the aircrews departed. Reporters and Manhattan Project officials gathered to document the historic moment.
The Enola Gay, unusually heavy with both bomb and extra fuel, took off just before 3 a.m. alongside Necessary Evil and the two other B-29s, The Great Artiste and Big Stink.
An hour earlier, three B-29s had taken off to report on weather conditions above the three principal targets.
Their information would determine where Tibbet’s would drop his lethal payload.
En route, as the Enola Gay passed over Iwo Jima, Parsons and his assistant, Lieutenant Jeppson, crawled into the bomb bay and successfully armed the bomb.
The aircraft then climbed to its operational altitude of 30,000feet. Soon, Tibbets was informed that Hiroshima was bathed in clear blue skies. It would be the principal target.
As the crew approached the city, bombardier Major Tom Ferebee – making use of the hours of preparation that had gone into this moment – took control.
He scanned for the Aioi Bridge—a familiar T-shaped landmark selected as the aiming point.
When it was in view, Ferebee initiated the final bomb run. Below, the population of the city were making their way to work, opening shops, and children arriving at school.
Civilians had no warning of what was coming. Families had only recently returned to their homes after a false air raid warning.
Eight-year-old Howard Kakita, visiting from the U.S., was playing with his brother when the bomb exploded.
Their grandmother, injured by shattered glass, managed to walk, bloodied but alive.
The boys escaped serious injury, but their once-grand home was engulfed in flames.
As they fled westward, they encountered endless scenes of horror: burned bodies lining the riverbanks, survivors with skin hanging from their limbs, and others pleading for water. Many who drank soon died, their internal injuries beyond saving.
Similarly, 13-year-old Setuko Thurlow had been working at a military office as part of Japan’s student mobilisation program when she saw a brilliant flash.
Moments later, she found herself buried under rubble.
Freed by a stranger’s voice, she emerged into a nightmare. Her friends were either crushed or burned alive.
She joined others fleeing toward the hills, surrounded by charred, groaning survivors.
They brought water to the dying and watched helplessly as the city burned through the night, with black radioactive soot raining from the sky.
Other survivors told stories of miraculous escapes, impossible injuries, and unthinkable sights.
Sumiko Ogata, a child at the time, carried her injured brother through fire and ruin, dodging collapsing bridges and stepping over bodies. Mitsuko Koshimizu, who had been attending school that morning, found herself digging out classmates and teachers from the rubble.
The imagery was haunting: people burned black, the lines between the living and dead blurred by pain and fire.
Everywhere, cries for help echoed into the void, with no medical services left to answer them.
The blast had obliterated 90 per cent of Hiroshima’s structures. Fourteen of the city’s sixteen hospitals were gone.
Nearly all medical personnel were dead. The fire brigade and emergency services were decimated. Communication lines were cut.
Train tracks were twisted and melted. Entire districts had vanished. What was once a thriving city was now a flattened, burning wasteland.
Despite the widespread devastation, Tokyo remained largely unaware. The initial state-run news bulletins downplayed the destruction.
Even local Japanese officials could not grasp the scale. With Hiroshima’s infrastructure destroyed, it was nearly impossible to coordinate relief.
In desperation, survivors fled into the surrounding mountains, seeking refuge.
In total, it’s estimated that 80,000 people died instantly, with tens of thousands more succumbing in the days and weeks that followed.
Back on Tinian, the mood was a surreal mix of triumph and exhaustion. The Enola Gay touched down at 2:58 p.m. (local time), and the crews were met by cheering officers and generals.
General Carl Spaatz, commander of U.S. Pacific Air Forces in the Pacific, pinned the Distinguished Service Cross on Tibbets’s chest.
When asked by General LeMay if there were more bombs, Tibbets confirmed there was another one—’Fat Man’—a plutonium bomb, ready for use.
The mission’s success was confirmed via telegrams to President Truman, who was aboard the USS Augusta as it steamed across the North Atlantic from his conference with Joseph Stalin and Winston Churchill at Potsdam.
Bursting with excitement, perhaps relief, he stood on his chair in the ship’s mess hall and declared to the watching crew that it was the greatest event in history.
The ship rang with cheers and whistles as the news spread across the ship.
Yet, for the men who had flown the mission, the sense of victory was tempered by an eerie quiet.
The usual high-spirited joking and celebration were noticeably absent.
Aboard Necessary Evil, the plane’s navigator, Lieutenant Russell Gackenbach, noted the strange silence in his plane: ‘Instead of relief, there was awe and an overwhelming awareness that they had participated in something the world had never seen before—something that would change warfare and humanity forever.’
From above, the mushroom cloud continued to rise, churning into the sky like a living force.
Tibbets later recalled that even Dante would have been terrified by what he saw.
For those on the ground, the aftermath was Dante’s Inferno made real.
Hiroshima, a port city once full of life that had launched the Imperial Japanese fleet that attacked Pearl Harbor on December 7, 1941 to start the war in the Pacific, had become a graveyard of ash and silence.
Iain MacGregor is a Fellow of the Royal Historical Society, and the author of The Hiroshima Men: The Quest to Build the Atomic Bomb, and the Fateful Decision to Use It (Constable).