American bomber pilot Paul Tibbets (centre) stands with the ground crew of Enola Gay, the plane Tibbets flew to Hiroshima. Photo: Wikicommons
A technician applies sealant and putty to the crevices of Fat Man. Photo: Wikicommons
Geophysicist and Manhattan Project participant Francis Birch (left) marks the bomb unit that would become Little Boy while Norman Ramsey, who would later win the Nobel Prize in Physics, looks on. Photo: Wikicommons
Soldiers check the casings on Fat Man. Several test bombs were created on Tinian Island -all were roughly identical to an operational bomb, even though they lacked the necessary equipment to detonate. Photo: Wikicommons
Fat Man is loaded onto a transport trailer before being fitted onto Enola Gay. Photo: Wikicommons
The atom bomb Little Boy, which killed 140,000 people in Hiroshima, at the Tannin Island. Photo: Wikicommons
Fat Man being lined up over a pit specifically constructed for it. The bomb was later loaded into the plane that eventually dropped it over Nagasaki. Photo: Wikicommons
Workers check Little Boy one last time, keeping the tarp on for security reasons. Photo: Wikicommons
Soldiers and workers sign their names and other messages on the nose of Fat Man. Photo: Wikicommons
The signatures on Little Boy. Photo: Wikicommons
The bomb was then escorted to the nearby north field airbase on Tinian island shrouded in tarp. Photo: Wikicommons
The tarp which shrouded the bomb is finally removed, finally ready to be loaded onto the aircraft. Photo: Wikicommons
The bomb after being secured inside the plane. Photo: Wikicommons
Enola Gay being reversed and positioned on the airstrip after Little Boy has been secured. Photo: Wikicommons
The uranium 235 gun-type bomb exploded at 8.16 am. Minutes after, Tibbets took this haunting image of the cloud which hung over Hiroshima. Photo: Wikicommons
Countdown to Hiroshima: secret images of the final days of Fat Man & Little Boy
In April 1945 the people of Hiroshima could have been forgiven for feeling lucky. At the height of World War II, conventional bombing of the city had, as if by a miracle, ceased.
But it was by method, not miracle.
Hiroshima was being spared so the full effect of a nuclear bombing could be observed.
On 6 August, 1945, Little Boy, the first of the only two nuclear weapons ever used, was dropped from the B-29 Bomber Enola Gay. It fell for 44.4 seconds, exploding nearly 2,000 feet above Hiroshima. 140,000 of Hiroshima's 350,000 residents were killed.
Three days later Bockscar, another B-29 bomber, flew over Nagasaki. Fat Man, as the bomb was called, missed its target by almost two miles. It still killed close to 40,000 people.
The bombing of Hiroshima and Nagasaki will forever stain the history of humanity. A war had been ended, but the severity of the price for peace will be debated for years to come.
In this series of formerly top secret pictures we take a look not at the destruction and the aftermath, but at the final moments of preparation before the bombing.
In July 1945, the island of Tinian was the unlikely setting for the final stages of the Hiroshima and Nagasaki bombings. Multiple pre-assemblies of each bomb made their way to the island's northern side - Little Boy by sea and Fat Man by air.
Awaiting them were the 509th Composite Group bombers Enola Gay and Bockscar that would carry out the actual bomb drops. The commander of the 509th was Colonel Paul Tibbets, the man who would eventually captain the Enola Gay on the Little Boy mission. The Enola Gay was actually named after Tibbets' mother. The bombing of Hiroshima was only the Enola Gay's third mission.
Since the bombs weren't weaponised before being transported to Tinian, experts like Francis Birch and Norman Ramsey were sent to the island to oversee the final assembly.
Birch had overseen the production of Little Boy and Ramsey would later earn himself a Nobel for physics. But in 1945 both found themselves on the tiny island of Tinian, manually tending to the bombs.
Both bombs were so heavy that special pits had to be built so that the bombs could be raised up into the bombers. Once inside the bombers they had to be manually armed.
The work done at Tinian in the month running up to the bombings were crucial in shaping the course of history. The crew was close enough to Japan to understand the cost of war, yet probably, even if they understood what the result would be, couldn't fathom the full horror of its aftermath. Or the place they would one day occupy in one of history's darkest chapters.
Text by Ranjan Crasta.