From the moment Henri Becquerel had discovered the nature of radioactivity in 1896, scientists had tried to harness the potential power of the atom. Crucially, in 1939, Niels Bohr had proved that nuclear fission was possible, and with this discovery the potential for a bomb of enormous power was clear.

But though Albert Einstein, at the insistence of other scientific colleagues, brought the importance of nuclear power to the attention of President Roosevelt in the autumn of 1939, it wasn’t until the entry of America into the Second World War as a result of Pearl Harbour that major efforts began in the United States to develop an atomic bomb. Up to this point most of the pioneering work had been done by scientists in Britain – in a project codenamed ‘Tube Alloys’ – but now the British allowed their discoveries to be further advanced in America.

This new American led operation – codenamed the ‘Manhattan Project’ – soon became the biggest single military construction project in history. Under the command of the brusque and demanding General Leslie Groves, scientists led by Robert Oppenheimer tried to solve both the theoretical and practical problems of creating a nuclear weapon. And they believed that the race to develop this new device was a race against time. ‘We start to develop the atomic bomb because we think the Germans are developing the atomic bomb,’ says Dr Conrad Crane. ‘If they’re going to use it against us we have to have it, and if we had got it ready before the Germans had surrendered [then] it would have been used against the Germans. We knew it was a war ending weapon, that’s what it was built for. We knew it was going to be an awful weapon.’

In reality, neither the Germans nor the Japanese had prioritized the development of a nuclear arsenal – though the Western Allies were not to know this for sure until after the war. As for the Soviets, they were years behind the Western Allies in the development of nuclear weapons; and the Americans and British decided not to inform their new ally about the Manhattan Project – something which demonstrates that for all their friendly rhetoric, the Western democracies did not fully trust their comrades in the East.

The first nuclear weapon was successfully tested at Alamogordo in New Mexico on 16 July 1945. President Truman, in Europe at the Potsdam Conference, now knew he had just become the most powerful leader in history. And the temptation to use this new weapon was almost irresistible.

‘I think one of the foremost forces of history most visible in the Second World War is what I call, slightly pompously, technological determinism,’ says Sir Max Hastings. ‘When weapons existed, and when fleets and air forces were created, they get used, and there was a moment at which Hungarian scientists went to the designated American Secretary of State, Byrnes, in 1945 and begged him to think before that atomic bomb was dropped. And Byrnes was furious with these scientists. He said the ‘US Congress are going to have a great deal to say if it emerges that we have spent two billion dollars on creating the most formidable weapon the world has ever seen and we didn’t use it’.

‘Now at this stage in the game it sounds facetious to talk in those terms because we have an understanding today of the enormity of nuclear weapons. We have an understanding that atomic bombs are not like other weapons, but it did not seem so plain to these people at the time. Plus I think one must see the decision to drop the bombs in the context of the fire bombing raids that had preceded them. The firebombing by B-29s armed with conventional incendiary weapons had already killed more Japanese than died at Hiroshima and Nagasaki, so any notion that there was a significant moral distinction between the two methods seems to be pretty questionable. I don’t think that many of those Japanese who suffered under those raids would have seen much difference between the two.’

But this is a point on which Professor Akira Iriye of Harvard University disagrees with Sir Max: ‘I do think it [the dropping of the nuclear bomb] was morally unacceptable, because people who used it could not quite tell the effect of nuclear radiation.’ Professor Iriye is also of the view that: ‘if the Japanese had done it then it probably would have been a war crime.’

But the talk at the Potsdam Conference in July 1945 was certainly not in terms of it being a ‘war crime’ to drop the atomic bomb. When Truman finally told Stalin, on 24 July 1945, about the existence of a ‘new weapon of unusual destructive force’, the Soviet leader merely remarked that he hoped the Americans would make good use of it against the Japanese.ⁱ (In fact, thanks to Soviet spies who were closely involved with the Manhattan Project, Stalin knew about the bomb long before Truman told him.)

Then there was another issue surrounding the use of the bomb that was hanging in the air. The sense in which the possession of this mighty weapon would be useful in dealing with Stalin – who at Potsdam, as far as the Western Allies were concerned, was not being as cooperative as he ought to have been. Churchill, according to Sir Alan Brooke, the Chief of the Imperial General Staff, was ‘completely carried away!’ by the possibilities of the bomb in this regard. ‘We now had something in our hands that could redress the balance with the Russians!’ Brooke reports Churchill as saying. ‘Now we could say if you insist on doing this or that, well we can just blot out Moscow then Stalingrad, then Kiev, then Kuibyshev, Kharkov…’ⁱⁱ

The final notable aspect at this stage of the decision making process was the insistence in the ‘Potsdam declaration’ that Japan should surrender to the Allies ‘unconditionally’. This term – ‘unconditional surrender’ – had first been introduced by President Roosevelt at the Casablanca conference in January 1943, but by now the American leadership knew from intelligence intercepts that a major block to any Japanese surrender was the future position of the Emperor. The Potsdam declaration was clear – there were to be no assurances given to the Japanese on that or any other matter. And yet, after the bombs had been dropped, the Americans hinted that if the Japanese surrendered now, then the institution of the Emperor was safe. Indeed, as it turned out, Emperor Hirohito, Japan’s wartime monarch and head of the Imperial Army, was permitted to continue as Emperor – now as a constitutional monarch – until his death in 1989. It was this curious situation which Henry Stimson, the US Secretary of War, was referring to when he later wrote: ‘History might find that the United States, by its delay in stating its position on unconditional surrender terms, had prolonged the war.’ⁱⁱⁱ

‘So I guess there’s big talk of the question of whether the United States might have been willing to let the Japanese keep the Emperor before the bomb was dropped,’ says Professor Iriye. ‘Truman gives the go ahead to the US Air Force to drop the bomb, I think something like on August 1st. If Truman had sent word that ‘we have this awful bomb that we could drop on you but we will let you keep the Emperor if you surrender right away’, would that have worked if the Emperor had been aware of this and had been consulted about it? I think he might have said ‘yes’, and many of the civilian leaders would have said ‘yes’. The armies would have said ‘no’, so the question does come down to whether the Emperor and his advisors and others in the navy would have been willing to fight the army.’

But it was a scenario that was never tested or tried. And so at just after eight o’clock on the morning of 6 August 1945 a B-29 bomber, commanded by Colonel Paul Tibbets and named the Enola Gay after his mother, dropped an atomic bomb on the city of Hiroshima. This target had been chosen after Kyoto had been spared because of it architectural splendour. Almost everything in Hiroshima was destroyed within five square miles of the point at which the bomb exploded. No one knows exactly how many people died as a result of the explosion – but one estimate is about 80,000 deaths within days, and tens of thousands more over time, of various illnesses caused by radiation.

President Truman heard the news about Hiroshima on board the ship taking him back to America from Potsdam. ‘I decoded it [the message about Hiroshima], and took it to Truman,’ says George Elsey, then a naval intelligence officer attached to the White House staff, ‘and the substance of it was very simply ‘Hiroshima bombed – greater effect than earlier tests’, and that was all that needed to be said. Truman was elated when he announced to the crew that we had a powerful new weapon and the war would certainly end – invasion [of Japan] would not be necessary… The crew just erupted in an explosion of hilarity and joy and shouts and the pounding of the desks and tables and so on. That was the mood in which we returned to Washington.’

A second atomic bomb was dropped on Nagasaki three days later. Then, on 15 August, Emperor Hirohito finally announced to the Japanese people that Japan had surrendered. The Second World War was finally over, but the debate about the morality of using atomic weapons had only just begun.

‘You ask how could you drop this immoral weapon?’ says Dr Conrad Crane. ‘Well, we’re looking at hundreds of thousands of casualties invading Japan, and even though American leaders know this bomb is going to kill a lot of Japanese civilians, their first obligation has got to be to their own people… I sometimes argue that the decision to use the atomic bomb is made on the 8th of December 1941 when FDR signs the order to start the project to build it. Once it gets built it’s going to get used, it’s just the nature of military technology in many ways.’

‘I attended a conference in Tokyo,’ says Dr Crane, ‘and I gave a presentation on [US General] Curtis LeMay burning down Tokyo [during the American firebombing of Japan] with a Japanese audience of historians and military officers… But at the end of it a senior Japanese historian stood up and said, "In the end, we must thank you Americans for the fire raids and the atomic bombs." Of course, I’m not quite sure what’s going to come next after this unusual lead in. But, again, everybody let him have this last word with us. And he said the reason was because "we were not ready to surrender. We probably would have surrendered eventually with the degradations of the submarine attacks and everything else by the end of 1945, but by that time the Soviets would have invaded Hokkaido as they were planning to do, and the end result would have been a North Japan and South Japan like East and West Germany, and Japan would have been divided between the Communists and the Americans. Our country may have never come back together again. And because of the fire raids and the atomic bombs it was enough of a shock to get us to surrender in the summer of 1945 before this partition could happen." He said that "we were eventually going to lose the war anyway and these actions forced us to surrender at a time that preserved our national unity for the future, and that would not have happened if the atomic bomb had not been used. So in hindsight," he said, "these were necessary." I thought it was an interesting perspective coming from the Japanese to say that. And, hindsight is always 20-20.’

Whilst acknowledging that there were those in the American administration who believed that the nuclear bomb was just ‘another weapon’ in the US arsenal, Professor Geoffrey Wawro also reminds us that ‘people like General Dwight Eisenhower and Fleet Admiral William Leahy were appalled by its use. They said that it was barbaric. But Truman was in the White House and the President has to make tough decisions and not pass the buck, so he took that decision and it did end the war and it doubtless saved tens of thousands of American lives.’

‘So it remains an open question,’ continues Professor Wawro, talking of whether or not Truman should have ordered the dropping of the atomic bomb. ‘But I’m sure there’s an awful lot of American families who are grateful that he took that decision. Another interesting consequence of that decision, of course, was that it allowed the Japanese to sort of wipe the whole slate clean. I mean, look what they did in World War Two. They fought a war as bestial as the German war. They engaged in genocide and mass rapes in cities like Nanking where soldiers were encouraged to ‘loot all, burn all and kill all’. They decimated China. And then their treatment of allied prisoners, whether Australians or British or American, was appalling. They reduced these people to gibbering wrecks by their exploitation and abuse of them. And yet by dropping the atomic bomb at Hiroshima and Nagasaki the Japanese Emperor afterwards was able to claim that they were a victim of this American technology, a sort of martyr if you will. And that, to this day, continues to affect our record of this war and our analysis of this war and the Japanese have still not owned up to the horrible things they did, which is in part because of the decision to drop the atom bombs. I don’t include that in a criticism of Truman’s decision because he clearly wasn’t thinking in that way, but that’s one of its impacts.’

--------------------------------------------------------------------------------------------------------------

ⁱ Laurence Rees, World War Two: Behind Closed Doors, BBC Books, 2009, p. 372
ⁱⁱ Entry for 23 July 1945 in Alex Danchev and Daniel Todman (eds.), Field Marshal Lord Alanbrooke, War Diaries 1939-1945, Phoenix, 2002, p. 709
ⁱⁱⁱ David F. Schmitz, Henry L Stimson: The First Wise Man, Scholarly Resources Inc., 2000, p. 205

RELATED PRODUCTS

Clicking on the items below will take you to our affiliate retailer.

• The Making of the Atomic Bomb
  Richard Rhodes
• Nemesis: The Battle for Japan, 1944-45
  Max Hastings
• Stalin and the Bomb
  David Holloway
• The Atomic Bomb and the Origins of the Cold War
  Campbell Craig
• Harry S. Truman and the Bomb: A Documentary History
  Robert H. Ferrell