There are still people who come to Hiroshima and Nagasaki to honor American relatives who were spared the task of invading mainland Japan. They may come to also honor the victims who died there, but they still see the atomic bombings as justified attacks against an aggressor, as attacks which led to fewer lives being lost on both sides of the conflict. Blame ultimately lies with the aggressor. This belief persists in spite of the large amount of historical research that has been done since 1945 which demolishes the argument that the bombs were necessary to end the war and that they were the essential cause of the Japanese decision to surrender.
It has been well demonstrated that the Japanese were no longer able to wage war and they were starving for food and fuel. A negotiated surrender was possible, especially on terms that required only that the emperor be retained as a symbolic head of the Japanese people. This condition was rejected in favor of pursuing an unconditional surrender, then after the surrender, the American occupying forces decided after all that Japan would be easier to manage if the emperor were kept in place. That fact alone should be enough to put an end to the assertion that the bombs were necessary to end the war, but then there is the additional fact that the Soviet declaration of war on August 9, 1945 made much more of an impression on the decision-makers in Tokyo. Over the next few days until the surrender on August 15, the bombs hardly registered in cabinet discussions as an issue to be worried about. It was just two other cities that had been bombed. Like other ruined cities all over Japan, they were regarded as acceptable sacrifices.
What bothers me most about the people who still hold onto this discredited view is the fact that they are often the same people who say very solemnly that atomic weapons must never be used again. We know now, apparently, but we didn’t know then. On the contrary, the nature of the new weapons was pretty well understood in 1945 in terms of the damage they could do with heat, blast and radiation, and everyone involved in the Manhattan Project understood what the effects would be on the nature of war and international relations. It was known that they would launch a horrific arms race. It was known that there would soon be much larger and deadlier hydrogen bombs. It was known that these weapons might put human life back in the Stone Age. Yet still it was decided that the situation was exceptional. America was faced with an implacable aggressor that had to be stopped, but it wanted to achieve its goals at minimal cost of American lives—an attitude that some of the highest officers serving at the time found dishonorable and also an unnecessary concern because, as mentioned above, they knew that Japan would soon have to surrender on terms favorable to America. The atomic bombs were a distraction, a billion-dollar bureaucratic juggernaut that rolled to its conclusion because no one powerful enough to stop it stood in its way.
I don’t intend to thoroughly rehash this argument that has been covered fully in other sources , , , , but I just mention what should be an obvious conclusion. If you think atomic bombs should never again be used in war, then you must also accept that they should not have been used in 1945. There is no reason to believe that circumstances similar to those of 1945 could not arise again: an aggressor starts a war–and the perception of who is the aggressor may be very subjective–but those who say it is an aggressor decide it must be stopped. However, as the conflict drags on and takes an unacceptable toll, the side trying to stop the aggressor becomes impatient and decides to just drop a nuke and be done with it. Most people today would say this should never happen, but it is exactly what happened in 1945.
In fact, American attitudes to this scenario were investigated by two researchers, Scott D. Sagan and Benjamin A. Valentino, and they found that little has changed since 1945. Americans still believe that military objectives should be achieved with minimum cost of American lives, no matter how many enemy civilians die. In the scenario they used in their survey they wanted to recreate the dilemma faced by the US in 1945. A report on their research described it thus:
... participants read a mock news article in which the U.S. places severe sanctions on Iran over allegations that Tehran has been caught violating the 2015 nuclear deal. In response, Iran attacks a U.S. aircraft carrier in the Persian Gulf, killing 2,403 military personnel (the same number killed by Japan at Pearl Harbor in 1941). Congress then declares war on Iran, and the president demands that Iran’s leadership accept “unconditional surrender.” U.S. generals give the president two options: mount a land invasion to reach Tehran and force the Iranian government to capitulate (at an estimated cost of 20,000 American fatalities), or shock Iran into unconditional surrender by dropping a single nuclear weapon on a major city near Tehran, killing an estimated 100,000 Iranian civilians (similar to the immediate death toll in Hiroshima). The poll’s participants were reminded that Iran doesn’t yet have an atomic weapon of its own. The results were startling: Under our scenario, 59% of respondents backed using a nuclear bomb on an Iranian city... Even when we increased the number of expected Iranian civilian fatalities 20 fold to two million, 59% of respondents—the same percentage supporting the nuclear attack with the lower death toll—still approved of dropping the bomb.
One major difference not covered in this survey is that if this scenario came true, public opinion and military planners would have to consider the possibility that nuclear armed nations might come to Iran’s defense. The unique circumstances of 1945 cannot be recreated. We now know that the world bristles with 15,000 atomic and hydrogen bombs and that an uncontrollable escalation that would destroy the world. In other words, the reasons for restraint are practical and selfish, not moral. Those who still justify Hiroshima and Nagasaki have a different attitude about the present or future use of nuclear weapons because they fear the repercussions on themselves, but disregard the violence that would be inflicted on the first target–that aggressor who had it coming, who had to be stopped.
If a nuclear weapon is ever used deliberately again, it’s a sure thing that the decision will be justified just as it was in 1945. It will be said that there was an implacable aggressor. They had to be stopped. We hoped it would save lives and shorten the war. Our intentions were good.
Hiroshima: Why the Bomb Was Dropped (ABC News, 1995)
 Gar Alperovitz, “Nuclear Attack on Japan Was Opposed by American Military Leadership,” Truth-out.org, January 14, 2014.
 Tsuyoshi Hasegawa, Racing the Enemy: Stalin, Truman, and the Surrender of Japan (Belknap, 2006).