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**President Truman in a August 9, 1945 radio address to the American people, outlined the reasons why we dropped the atomic bomb on Hiroshima (and later Nagasaki)

I realize the tragic significance of the atomic bomb. Its production and its use were not lightly undertaken by this Government. But we knew that our enemies were on the search for it. We know now how close they were to finding it. And we knew the disaster, which would come to this Nation, and to all peace-loving nations, to all civilization, if they had found it first. That is why we felt compelled to undertake the long and uncertain and costly labor of discovery and production.**

We won the race of discovery against the Germans. Having found the bomb we have used it. We have used it against those who attacked us without warning at Pearl Harbor, against those who have starved and beaten and executed American prisoners of war, against those who have abandoned all pretense of obeying international laws of warfare. We have used it in order to shorten the agony of war, in order to save the lives of thousands and thousands of young Americans.

How many lives did Truman's military experts estimate would be saved (on the Japanese/American sides) by dropping the two atom bombs?

How many lives do modern military historians estimate were saved by the two atom bombs?

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I don't know how well this can be answered given that there's still some expert dispute, though many estimates put it in the millions –  Avi Sep 19 '13 at 3:14
@Avi, the first question can be answered (Truman obviously was basing his "thousands of lives" off of some military analysts projections) The second part cannot be answered definitely, but it can be answered. (I don't know who would be considered an authority on the matter, suggestions?) Good answers will cite experts that back up their figures with troop numbers, planned attacks, etc. –  user1873 Sep 19 '13 at 3:24
The answers vary wildly, is the problem. According to Thomas Childers in his lecture on WWII in the teaching company, most estimated that hundreds of thousands or even millions of Japanese and American lives were saved, though at least one estimate thought that an invasion would end up with a few tens of thousands fewer deaths. –  Avi Sep 19 '13 at 5:12
The questions in the body text can be answered. I'll change the title to reflect this. –  Lennart Regebro Sep 19 '13 at 13:31
I voted to close: This question is about alternative history. and can be answered only by speculation and guesstimation. The A Bomb was used, so we can never know what would have been had it not been used. Wars are notoriously unpredictable - there is no telling what would have been the outcome had the USA not used the A Bomb. –  Vector Sep 19 '13 at 17:56

4 Answers 4

This is a matter of very hot debate. It depends on what assumptions you make about what would have happened in the future. But there are two basic scenarios:

  1. The bombings saved somewhere in the neighborhood of 250 - 500 thousand US lives, and Japanese lives in the millions.
  2. The bombings saved US lives numbered only in the thousands, and actually cost the Japanese up to a quarter of a million lives.

To my mind nobody is in a better position to make estimates of what a full-blown invasion would cost in lives than the people who were in charge of the armed forces at the time. Lukily for us, the US armed services did estimates for their own purposes before the A-bombs were dropped.

The Army estimated they would suffer 7.45 casualties/1,000 man-days and 1.78 fatalities/1,000 man-days in an invasion. So assuming the invasion of Kyūshū took 90 days, that works out to about half a million US Army wounded, and over 100,000 dead. If they then needed to invade Honshū and take the Capitol in another 90 day campaign, that would more than double the toll to about 1.2 million wounded, and over a quarter of a million US Army dead. This is about the lowest estimate you will find from Army sources, but being the most detailed I give it the most credence. But you should be aware there were numbers much higher floating around that decision-makers in the USA would have been hearing.

Interestingly, on this basis, the Army put in an order for about half a million Purple Hearts (the medal given for combat wounds of any kind). They have been working through this stockpile ever since, and still have over 100,000 of them left.

This did not cover Japanese casualties though. Presumably they would be even higher. This is all based on the assumption that the defence from the Japanese military and civilians would be simliar to what was encountered in Okinawa.

The Atomic bombings themselves are estimated to have killed about 150,000–246,000 people (almost all Japanese of course).

Both at the time and today there were those who claimed the Japanese would not have fought like they did on Okinawa, and in fact were close to surrendering in a way acceptable to the US. If they happen to be correct, then the death toll from the bombing is rather massively in the red (on the Japanese side. On the US side, it still saved lives). But we have no real way of knowing this. I know there are some documents floating around that some claim prove otherwise, but I'd posit anyone who insists some documents prove future actions of politicians has a poor (or idealistic) understanding of politicans.

Which side a person believes to me seems to have far more to do with what country that person hails from and/or how that person feels about Atomic Weaponry in general, than anything else. So the hope of there being a single impartial number that isn't somehow tainted by politics is remote in the extreme.

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+1 "Was the Japanese ready to surrender before Hiroshima" would also be a good question. (The answer is a pretty emphatic "no"). –  Lennart Regebro Sep 19 '13 at 16:19
We might want to consider, however highly speculative, that the mere fact of dropping those bombs, might have deterred from dropping other bombs later during the cold war. I.e. if those bombs weren't dropped, sooner or later a bomb would have been dropped anyway. –  Lohoris Apr 1 at 11:09
I don't doubt the Army estimates. I also do not doubt that the nuclear bombings shortened the war, in a purely "time" sense. But I doubt that it would have been necessary to take the whole of Kyūshū and Honshū by invasion to enforce a surrender. –  DevSolar Apr 8 at 13:43
"...the Army put in an order for about half a million Purple Hearts....They have been working through this stockpile ever since, and still have over 100,000 of them left." That's amazing. Thank you for sharing. –  Kyle Strand Apr 10 at 20:50

It is impossible to say how many lives were saved by the atomic bombing of Japan because no one knows when Japan would have surrendered if the bombs had not been dropped. However, it is likely that the war would have gone on for many months and culminated in the US invasion planned for November 1, 1946. In that case, many tens of thousands, if not hundreds of thousands of Japanese would have died from the continued B29 bombings using conventional bombs. Also, remember that heavy fighting was still going on in China where it is estimated that 10,000 Chinese were dying every month. Also the Russians had just started attacking Japanese forces in Manchuria and Korea. Who knows how many casualties that campaign might have inflicted in those months. If the invasion had taken place, the number of casualties on both sides would have been very high because the Japanese were intending to defend their homeland with everything they had (including 5000 Kamikaze planes and hundreds of kamikaze motor boats. They hoped that by inflicting significant American casualties, the US would agree to peace terms more favorable to Japan. Also, the US planned to drop 3 atomic bombs as a prelude to the invasion. The effect of such an action cannot even be estimated. As a further point, if the atomic bombs had not been dropped on Hiroshima and Nagasaki, then it is very likely that both cities would have been the targets of conventional B29 bombings which probably would have resulted in close to the same number of casualties (100,000 Japanese died in the first fire bombing of Tokyo by B29s). As references for the above, I cite the following sources:

 The Fall of Japan, William Craig, The Dial Press, 1967
 Japan Subdued, The Atomic Bomb and the End of the War in the Pacific, Herbert Feis,
    Princeton University Press, 1961
 The Invasion of Japan Alternative to the Bomb, John Ray Skates, University of South
    Carolina Press,  
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It's a negative number; the bombs were militarily unnecessary to secure the Japanese surrender. The US Strategic Bombing Survey, released 1946, estimated that:

Based on a detailed investigation of all the facts, and supported by the testimony of the surviving Japanese leaders involved, it is the Survey's opinion that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.

This was a group primarily comprised of military leaders, though with a sizable civilian contingent. In their measured opinion, the Japanese could not have sustained the war more than a few additional months.

They also present evidence that the Emperor wanted peace:

The talks by the Japanese ambassador in Moscow and with the Soviet ambassador in Tokyo did not make progress. On 20 June the Emperor, on his own initiative, called the six members of the Supreme War Direction Council to a conference and said it was necessary to have a plan to close the war at once, as well as a plan to defend the home islands. The timing of the Potsdam Conference interfered with a plan to send Prince Konoye to Moscow as a special emissary with instructions from the cabinet to negotiate for peace on terms less than unconditional surrender, but with private instructions from the Emperor to secure peace at any price. Although the Supreme War Direction Council, in its deliberations on the Potsdam Declaration, was agreed on the advisability of ending the war, three of its members, the Prime Minister, the Foreign Minister and the Navy Minister, were prepared to accept unconditional surrender, while the other three, the Army Minister, and the Chiefs of Staff of both services, favored continued resistance unless certain mitigating conditions were obtained.

The common interpretation, especially among revisionists, is that Truman and the US were aggressive in preparation for the post-war world and competition with the Soviets. I'm not expressing an opinion on this point, but I am relaying the theory.

In any case, the dropping of the bombs was needless. Japan lacked the resources and strength to keep the fight going. Blockade and targeted conventional bombing could have contained them until they finally sued for peace. It appears from the historical record that the Japanese leadership already saw the writing on the wall and was preparing for the inevitable defeat several months before the US dropped bombs on civilian population centers.

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You fail to quote the critical paragraph of that report: On 6 August the atomic bomb was dropped on Hiroshima, and on 9 August Russia entered the war. In the succeeding meetings of the Supreme War Direction Council, the differences of opinion previously existing as to the Potsdam terms persisted exactly as before. By using the urgency brought about through fear of further atomic bombing attacks, the Prime Minister found it possible to bring the Emperor directly into the discussions of the Potsdam terms. Hirohito, acting as arbiter, resolved the conflict in favor of unconditional surrender. –  Pieter Geerkens Apr 1 at 1:34
It's not equivocal. In their opinion, the war would have ended with a few months without the bombs. I don't think nuking two cities was justified by shortening the blockade a few months. Given the state of the war for Japan, and their resource shortages, the surrender was incredibly likely. –  NL7 Apr 1 at 4:10
@Pieter - I agree they were self-serving. But I also think they were correct. Japan did not have the resources to mount an effective campaign and the highest leadership was discussing surrender options months before the bombs dropped. The argument that the bombs fundamentally changed Japanese elite opinion is weak. –  NL7 Apr 1 at 14:13
@jwenting - The argument is not that it did not shorten the war, since it certainly did. But if it only shortened it by two to four months, and the invasion was not slated to happen until mid to late 1946, then it did not "save lives" of the invading force. The contention of the USSBS, which was released in 1946 and was staffed mostly by the military and not hippies, is that without the bombs Japan would have surrendered from an embargo with comparatively minor loss of US lives. In other words, the lives taken by the bombs outweighed the lives saved. –  NL7 Apr 1 at 14:15
You can't accept the top answer citing the Army's casualty estimates and at the same time flaming this answer for citing SAC papers just because you agree with the one answer and disagree with the other. –  DevSolar Apr 8 at 13:39

I don't think it "saved" any lives, as the bombs didn't actually end the war.

Japan was not afraid of this new technology and were not going to surrender just because a new "bigger" bomb was being used against them.

What happened was that, shortly after the bombings, the USSR declared war on Japan. Once that happened, Japan immediately surrendered because they did not have the capacity to fight BOTH the USA and USSR.

Here is an article which fully explains what happened:


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This is one opinon (as I mentioned). I'd look on it a bit better if you had mentioned the folks who believe this more prominently. For example, the author of that linked article is Ward Wilson. He is essentially a life-long anti-nuclear weapon activist. Nothing nessecarily wrong with that, but you can see how such a person would have an interest in exactly the argument he was making. The popular idea that nuclear bombs ended the war is a huge hinderance to someone who is out right now arguing they are useless and should all be abandoned. –  T.E.D. Sep 24 '13 at 14:05
... this is exactly what I was getting at when I said which view you take says more about you than it does the actual history of the matter. –  T.E.D. Sep 24 '13 at 14:08
There's something to it, too bad there are no sources for the information regarding Japanese Supreme Council. –  kubanczyk Sep 24 '13 at 16:14
Did the Soviets do more than take the Kuriles and Sakhalin? Seems like a bluff. –  NL7 Apr 1 at 4:07
@NL7 they were set to invade mainland Japan when Japan surrendered. Had that happened, it might well have ended in a fight between US and Soviet forces over Honshu. –  jwenting Apr 1 at 7:13

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