Was the US justified in dropping atomic bombs on Hiroshima and Nagasaki during the Second World War?

His decision was mainly based on the estimate of half a million Allied casualties likely to be caused by invading the home islands of Japan. There was also the likely death rate from starvation for Allied PoWs and civilians as the war dragged on well into 1946.

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What Truman did not know, and which has only been established quite recently, is that the Imperial Japanese Army could never contemplate surrender, having forced all their men to fight to the death since the start of the war. All civilians were to be mobilised and forced to fight with bamboo spears and satchel charges to act as suicide bombers against Allied tanks. Japanese documents apparently indicate their army was prepared to accept up to 28 million civilian deaths.

Antony Beevor is a bestselling military historian, specialising in the Second World War. His most recent book is Ardennes 1944: Hitler’s Last Gamble (Viking, 2015)

“No. It was immoral, and unnecessary” – Richard Overy

The dropping of the atomic bomb on Hiroshima was justified at the time as being moral – in order to bring about a more rapid victory and prevent the deaths of more Americans. However, it was clearly not moral to use this weapon knowing that it would kill civilians and destroy the urban milieu. And it wasn’t necessary either.

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Militarily Japan was finished (as the Soviet invasion of Manchuria that August showed). Further blockade and urban destruction would have produced a surrender in August or September at the latest, without the need for the costly anticipated invasion or the atomic bomb. As for the second bomb on Nagasaki, that was just as unnecessary as the first one. It was deemed to be needed, partly because it was a different design, and the military (and many civilian scientists) were keen to see if they both worked the same way. There was, in other words, a cynical scientific imperative at work as well.

I should also add that there was a fine line between the atomic bomb and conventional bombing – indeed descriptions of Hamburg or Tokyo after conventional bombing echo the aftermath of Hiroshima. To regard Hiroshima as a moral violation is also to condemn the firebombing campaign, which was deliberately aimed at city centres and completely indiscriminate.

Of course it is easy to say that if I had been in Truman’s shoes, I would not have ordered the two bombings. But it is possible to imagine greater restraint. The British and Americans had planned in detail the gas-bombing of a list of 17 major German cities, but in the end did not carry it out because the moral case seemed to depend on Germany using gas first. Restraint was possible, and, at the very end of the war, perhaps more politically acceptable.

Richard Overy is a professor of history at the University of Exeter and editor of The Oxford Illustrated History of World War Two (OUP, 2015)

“Yes. It was the least bad option” – Robert James Maddox

The atomic bombs were horrible, but I agree with US secretary of war Henry L Stimson that using them was the “least abhorrent choice”. A bloody invasion and round-the-clock conventional bombing would have led to a far higher death toll and so the atomic weapons actually saved thousands of American and millions of Japanese lives. The bombs were the best means to bring about unconditional surrender, which is what the US leaders wanted. Only this would enable the Allies to occupy Japan and root out the institutions that led to war in the first place.

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The experience with Germany after the First World War had persuaded them that a mere armistice would constitute a betrayal of future generations if an even larger war occurred 20 years down the line. It is true that the radiation effects of the atomic bomb provided a grisly dividend, which the US leaders did not anticipate. However, even if they had known, I don’t think it would have changed their decision.

Robert James Maddox is author of Hiroshima in History: The Myths of Revisionism (University of Missouri Press, 2007)

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“No. Japan would have surrendered anyway” – Martin J Sherwin

I believe that it was a mistake and a tragedy that the atomic bombs were used. Those bombings had little to do with the Japanese decision to surrender. The evidence has become overwhelming that it was the entry of the Soviet Union on 8 August into the war against Japan that forced surrender but, understandably, this view is very difficult for Americans to accept.

Of the Japanese leaders, it was the military ones who held out against the civilian leaders who were closest to the emperor, and who wanted to surrender provided the emperor’s safety would be guaranteed. The military’s argument was that Japan could convince the Soviet Union to mediate on its behalf for better surrender terms than unconditional surrender and therefore should continue the war until that was achieved.

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Once the USSR entered the war, the Japanese military not only had no arguments for continuation left, but it also feared the Soviet Union would occupy significant parts of northern Japan.

Truman could have simply waited for the Soviet Union to enter the war but he did not want the USSR to have a claim to participate in the occupation of Japan. Another option (which could have ended the war before August) was to clarify that the emperor would not be held accountable for the war under the policy of unconditional surrender. US secretary of war Stimson recommended this, but secretary of state James Byrnes, who was much closer to Truman, vetoed it.

By dropping the atomic bombs instead, the United States signalled to the world that it considered nuclear weapons to be legitimate weapons of war. Those bombings precipitated the nuclear arms race and they are the source of all nuclear proliferation.

The late Martin J Sherwin was co-author of American Prometheus: The Triumph and Tragedy of J Robert Oppenheimer (Atlantic, 2008)

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“Yes. It saved millions of lives in Japan and Asia” – Richard Frank

Dropping the bombs was morally preferable to any other choices available. One of the biggest problems we have is that we can talk about Dresden and the bombing of Hamburg and we all know what the context is: Nazi Germany and what Nazi Germany did. There’s been a great amnesia in the west with respect to what sort of war Japan conducted across Asia-Pacific. Bear in mind that for every Japanese non-combatant who died during the war, 17 or 18 died across Asia-Pacific. Yet you very seldom find references to this and virtually nothing that vivifies it in the way that the suffering at Hiroshima and Nagasaki has been.

With the original invasion strategy negated by radio intelligence revealing the massive Japanese build-up on the planned Kyushu landing areas, Truman’s alternative was a campaign of blockade and bombardment, which would have killed millions of Japanese, mostly non-combatants. For example, in 1946 the food situation would have become catastrophic and there would have been stupendous civilian deaths. It was only because Japan surrendered when it still had a serviceable administrative system – plus American food aid – that saved the country from famine.

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Another thing to bear in mind is that while just over 200,000 people were killed in total by the atomic bombs, it is estimated that 300,000–500,000 Japanese people (many of whom were civilians) died or disappeared in Soviet captivity. Had the war continued, that number would have been much higher.

Critics talk about changing the demand for unconditional surrender, but the Japanese government had never put forth a set of terms on which they were prepared to end the war prior to Hiroshima. The inner cabinet ruling the country never devised such terms. When foreign minister Shigenori Togo was told that the best terms Japan could obtain were unconditional surrender with the exception of maintaining the imperial system, Togo flatly rejected them in the name of the cabinet.

The fact is that there was no historical record over the past 2,600 years of Japan ever surrendering, nor any examples of a Japanese unit surrendering during the war. This was where the great American fear lay.

Richard B Frank is a military historian whose books include Downfall: The End of the Imperial Japanese Empire (Random House, 1999)

“No. Better options were discarded for political reasons” – Tsuyoshi Hasegawa

Once sympathetic to the argument that the atomic bomb was necessary, the more research I do, the more I am convinced it was one of the gravest war crimes the US has ever committed. I’ve been to Japan and discovered what happened on the ground in 1945 and it was really horrifying. The radiation has affected people who survived the blast for many years and still today thousands of people suffer the effects.

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There were possible alternatives that might have ended the war. Truman could have invited Stalin to sign the Potsdam declaration [in which the USA, Britain and Nationalist China demanded Japanese surrender in July 1945]. The authors of the draft of the declaration believed that if the Soviets joined the war at this time it might lead to Japanese surrender but Truman consciously avoided that option, because he and some of his advisors were apprehensive about Soviet entry. I don’t agree with revisionists who say Truman used the bomb to intimidate the Soviet Union but I believe he used it to force Japan to surrender before they were able to enter the war.

The second option was to alter the demand for unconditional surrender. Some influential advisors within the Truman administration were in favour of allowing the Japanese to keep the emperor system to induce so-called moderates within the Japanese government to work for the termination of the war. However, Truman was mindful of American public opinion, which wanted unconditional surrender as revenge against Pearl Harbor and the Japanese atrocities.

Bearing in mind those atrocities, it’s clear that Japan doesn’t have a leg to stand on when it comes to immoral acts in the war. However, one atrocity does not make another one right. I believe this was the most righteous war the Americans have ever been involved in but you still can’t justify using any means to win a just war.

Tsuyoshi Hasegawa is a professor of history at the University of California at Santa Barbara and the author of Racing the Enemy: Stalin, Truman, and the Surrender of Japan (Harvard University, Press 2005)

“Yes. The moral failing was Japan’s” – Michael Kort

Truman’s decision to use the atomic bomb was the best choice available under the circumstances and was therefore morally justifiable. It was clear Japan was unwilling to surrender on terms even remotely acceptable to the US and its allies, and the country was preparing a defence far more formidable than the US had anticipated.

The choice was not, as is frequently argued, between using an atomic bomb against Hiroshima and invading Japan. No one on the Allied side could say with confidence what would bring about a Japanese surrender, as Japan’s situation had been hopeless for a long time. It was hoped that the shock provided by the bombs would convince Tokyo to surrender, but how many would be needed was an open question. After Hiroshima, the Japanese government had three days to respond before Nagasaki but did not do so. Hirohito and some of his advisers knew Japan had to surrender but were not in a position to get the government to accept that conclusion. Key military members of the government argued that it was unlikely that the US could have a second bomb and, even if it did, public pressure would prevent its use. The bombing of Nagasaki demolished these arguments and led directly to the imperial conference that produced Japan’s offer to surrender.

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The absolutist moral arguments (such as not harming civilians) made against the atomic bombs would have precluded many other actions essential to victory taken by the Allies during the most destructive war in history. There is no doubt that had the bomb been available sooner, it would have been used against Germany. There was, to be sure, a moral failing in August 1945, but it was on the part of the Japanese government when it refused to surrender after its long war of conquest had been lost.

Michael Kort is professor of social science at Boston University and author of The Columbia Guide to Hiroshima and the Bomb (Columbia Press, 2007)

This article was first published in the August 2015 issue of BBC History Magazine

HistoryExtra readers George Evans-Hulme and Roy Ceustermans debate...

George Evans-Hulme: Yes, it was justified. The US was, like the rest of the world, soldiering on towards the end of a dark period of human history that had seen the single most costly conflict (in terms of life) in history, and they chose to adopt a stance that seemed to limit the amount of casualties in the war, by significantly shortening it with the use of atomic weapons.

It was certainly a reasonable view for the USA to take, since they had suffered the loss of more than 418,000 lives, both military and civilian. To the top rank of the US military the 135,000 death toll was worth it to prevent the “many thousands of American troops [that] would be killed in invading Japan” – a view attributed to the president himself.

This was a grave consequence taken seriously by the US. Ordering the deployment of the atomic bombs was an abhorrent act, but one they were certainly justified in doing.

Roy Ceustermans: No, the US wasn’t justified. Even secretary of war Henry Lewis Stimson was not sure the bombs were needed to reduce the need of an invasion: “Japan had no allies; its navy was almost destroyed; its islands were under a naval blockade; and its cities were undergoing concentrated air attacks.”

The United States still had many industrial resources to use against Japan, and thus it was essentially defeated. Rear Admiral Tocshitane Takata concurred that B-29s “were the greatest single factor in forcing Japan's surrender”, while Prince Konoye already thought Japan was defeated on 14 February 1945 when he met emperor Hirohito.

A combination of thoroughly bombing blockading cities that were economically dependent on foreign sources for food and raw materials, and the threat of Soviet entry in the war, would have been enough.

The recommendations for the use of the bomb show that the military was more interested in its devastating effect than in preparing the invasion. Therefore the destruction of hospitals and schools etc was acceptable to them.

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GEH: The USA was more interested in a quick and easy end to the war than causing untold suffering. They had in their hands a weapon that was capable of bringing the war to a swift end, and so they used it.

The atom bombs achieved their desired effects by causing maximum devastation. Just six days after the Nagasaki bombing, the Emperor’s Gyokuon-hōsō speech was broadcast to the nation, detailing the Japanese surrender. The devastation caused by the bombs sped up the Japanese surrender, which was the best solution for all parties.

If the atomic bombs had not had the devastating effect they had, they would have been utterly pointless. They replaced thousands of US bombing missions that would have been required to achieve the same effect of the two bombs that, individually, had the explosive power of the payload of 2,000 B-29s. This freed up resources that could be utilised for the war effort elsewhere.

RC: After the bloody battles of Iwo Jima and Okinawa, the death toll on both sides was high, and the countries’ negative view of one other became almost unbridgeable, says J Samuel Walker in Prompt and Utter Destruction: Truman and The Use of Atomic Bombs Against Japan. Therefore, the US created unconditional terms of surrender, knowingly going against the Japanese ethic of honour and against the institute of the emperor, whom most Americans probably wanted dead.

Consequently, the use of the atomic bomb became a way to avenge America's fallen soldiers while also keeping the USSR in check in Europe. The Japanese civilian casualties did not matter in this strategy. Also, it did not prevent the Cold War, as the USSR was just a few years behind on a-bomb research.

At the time, revenge, geopolitics and an expensive project that could not be allowed to simply rust away, meant the atomic bomb had to be hastily deployed “in the field” in order to see its power and aftermath – though little was known about radiation and its effects on humans.

GEH: Admittedly, the US did use the atom bomb to keep the USSR in line, and for that it served its purpose. It may not have stopped the Soviets developing their own nuclear device, but that’s not what it was intended for. It was used as a deterrent to keep the (sometimes uneasy) peace between the US and the USSR, and it achieved that. There are no cases of a direct, all-out war between the US and the Soviets that can be attributed to the potentially devastating effects of atomic weaponry.

The atomic bombs certainly established US dominance immediately after the Second World War – the destructive power it possessed meant that it remained uncontested as the world’s greatest power until the Soviets developed their own weapon, four years after the deployment at Nagasaki. It is certainly true that Stalin and the Soviets tried to test US dominance, but even into the 1960s the US generally came out on top.

RC: The price to keep the USSR in check was steep: the use of a weapon of mass destruction that caused around 200,000 deaths (most of them civilians) and massive suffering through radiation. However, it did not stop the USSR from creating the same weapon within four years.

It might be argued that, following the explosions, Japan virtually disappeared from the world stage while the USSR viewed the bombing as an incentive to acquire the same weaponry in order to retaliate in equal force if the atomic bomb was ever used again. Considering the tension between the two countries, a similar attack with tens of thousands of civilian casualties would have created a nuclear apocalypse.

If the US had organised a demonstration, as they had briefly considered, the USSR would still have responded in the same manner, while Japan – which had made clear overtures for a (un)conditional surrender – could have been spared. Furthermore, by postponing the use of the bomb, scientists would have had time to understand the test results, meaning further anguish, like the Bikini Atoll [a huge US hydrogen bomb test in 1954 that had major consequences for the geology and natural environment, and on the health of those who were exposed to radiation] could have been avoided.

GEH: The large civilian death toll that resulted from the bombings can be seen as a small price to pay by the United States in return for their assertion of dominance on the world stage.

The USSR’s development of an atomic weapon had been underway since 1943, and so their quest for nuclear devices cannot be solely attributed to the events of Hiroshima and Nagasaki. It should also be considered that the Soviets’ rapid progress in creating an atom bomb was not exclusively down to their desire to compete with the United States, but from spies passing them US secrets.

Postponing the use of the atom bomb would only have prolonged the war and potentially created an even worse fate for the people of Japan, with an estimated five to 10 million Japanese fatalities – a number higher than some estimates for the entire Soviet military in the Second World War.

Ultimately, the atomic bombs did what they were designed to do. They created such a high level of devastation that the Japanese felt they had no option but to surrender unconditionally to the United States, hence resulting in US victory and the end of the Second World War.

RC: Of course civilian casualties of another nation would have been acceptable to the USA. Japan had made clear overtures to peace, but cultural differences made this nearly impossible (the shame of unconditional surrender goes against their code of honour).

The determination to use an expensive bomb instead of letting it rust away; the desire to find out how devastating it was and the opportunity to use the bomb as a strong showcase of US supremacy, made Japan the ideal target.

Obviously, the USSR would eventually succeed in creating the a-bomb. Therefore, making Hiroshima & Nagasaki the example of the tremendous power of the bombs would make it clear to the USSR that they too needed such weapons to defend themselves.

Moreover, other countries claimed the right of nuclear weapons to defend their citizens. Consequently, the tragic bombings became the example of an arm’s race instead of peace.

Furthermore, since Japan was already on the brink of collapse the bombing was unnecessary, and peace talks would have taken place within a decent time frame (even after the cancelled Hawaii summit). The millions of deaths calculated by Operation Downfall [the codename for the Allied plan for the invasion of Japan near the end of the Second World War, which was abandoned when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki] actually show that only desperation and honour stood between Japan and unconditional surrender.

George Evans-Hulme has a passion for military and political history, and enjoys visiting historical sites across the UK.

Roy Ceustermans has a master's degree in the history of the Catholic Church, an advanced master's degree on the historical expansion, exchange and globalisation of the world, and a master’s degree in management.