Why didn't they use Little Boy as a tactical nuclear weapon?

CalBear

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Operation Olympic was sheduled for November 1945 which was only the invasion of Kyushu island. They said they would have 7 bombs ready by that time. The attack on the main island Honshu was sheduled for March 1st 1946, imagine how many bombs they would have ready by then. Plenty.


Actually it would only have been about 8-10 more. The fissile material was not really being mass produced yet. That took several years.
 
Actually it would only have been about 8-10 more. The fissile material was not really being mass produced yet. That took several years.

Is that the OTL number?

IIRC OTL the original haphazard production was cancelled in favor of new assembly. If the US is still at war, we might see both production going at the same time.
 
If it is a matter of considering options, another sensible way that A-bombs come up in a combat context rather than strategic war-ending weapon would be to consider using them in China.

By summer 1945, the IJN was a spent force, the IJA on the other hand still held much of China. The die-hard anti-surrender elements would I suppose have been largely Army generals who knew their forces on the continent were still undefeated.

So an alternative war plan to the options of either A-bombing Japan or invading Japan, or doing nothing more than starving out Japan, would be for the Allies to greatly raise the pressure on the Japanese stronghold in China.

That's the context in which I'd think use of nukes "tactically" would come up. Though the point is, to amass sufficient enemy force so that the rare and expensive and tricky to deliver giant bomb gets a whole lot of enemies at once--such a scale of death would I'd think pretty much automatically cross the line from "tactical" to "strategic," though not in the sense that we speak of "strategic bombing" or "strategic nuclear weapons"--these are intended to win wars first of all by inflicting levels of damage such that the enemy is deterred from war as an option, second if they are foolish enough to refuse to be deterred, devastate their ability, not as armies but as a society, to fight the war.

"Tactical" use of even the relatively "small" nukes Los Alamos was first able to make merely means using them in contexts where such deterrance/total devastation is not intended or expected; the scale of damage they do hardly fits the sort of image the word "tactical" normally conjures up!

Someone should point out, in addition, as CalBear mentioned, to there being a limited supply of fissionable materials, the early A-bombs of either design (Gun-Uranium aka "Little Boy"; implosion-Plutonium aka "Fat Man") were very heavy by WWII bomb standards; Americans could only deliver them with the B-29, a specially modified version at that just capable of carrying one bomb, and while some British bombers would have less trouble accommodating the bomb, being lower-altitude and I believe slower than the stratospheric, pressurized Superfortress, these British bombers would be unlikely to survive their own bomb!

What is more, as late as the Operation Crossroads Bikini tests some years after the war, the first "shot" of the planned three tests, "Able," was delivered by the Air Force as an air drop. They missed the intended target by nearly a mile! It very largely invalidated the shot as far as scientific value was concerned. And demonstrated the difficulty of aiming an A-bomb at this stage.

That doesn't matter so much when one has a frankly "strategic" target such as a city, that is sitting immobile in a known location with known defenses.

In a battlefield context, especially one like China, where the enemy probably won't be doing what you hope or want them to, the precise best target may not be known and if known will be shifting. Add to the bomber crew's apparent inability to strike within less than half a mile of their target when that target is known and hitting it has been practiced, uncertain communications betweeen different divisions of the Army (as the Air Force at the time would still have been technically part of the Army) and the uncertainties of the commanders calling for the airstrike--well, if we had hundreds of A-bombs to spare I suppose nuclear whack-a-mole might have been effective against the IJA in China, though probably horribly costly to the Allied armies too.

I have to admit, using them "tactically" to support an invasion makes more sense. There at least it is the Allies choosing the field of battle whereas the enemy is pretty much forced to respond by concentrating forces in predictable locations, or forfeit a beachhead to their foes. If you've got limited numbers of bombs, that's really the only way to plan to use them in an actual combat situation, to somehow force the enemy to make using it worth your while by perforce having to concentrate at the target.

But the horrible aspects of such a battle, with Allied troops hopefully not but possibly themselves blasted by the bomb, then having to advance directly into the just-nuked blast zone, no doubt to have to dig in just beyond it--or in the middle of it!:eek: against more Japanese defenders, all in the service of an invasion expected to be a major bloodbath on both sides--well, it is a good thing the Japanese surrendered before it came to that.
 
Actually it would only have been about 8-10 more. The fissile material was not really being mass produced yet. That took several years.

Are you using the 2 and a bit per month figure? Because that doesn't take into account the improvements being made to production and bomb design.

Los Alamos was actively pursuing levitated composite core designs, which would have been operational in the near future - Oppenheimer actually suggested breaking up Little Boy to make four composite bombs, but Groves preferred one bomb now to four bombs in a month. This would have radically improved their efficiency of using fissile material. Bomb design improvements would have allowed them to make 6 bombs per month using their existing fissile production rate. Production of fissiles was also increasing as they worked the kinks out of the Oak Ridge complex; combining the two would increase production to 10 bombs per month. Alternatively they could have produced a smaller number of higher-yield devices.

IOTL, the war ended and everybody went home, and it took a few more years before we started using composite cores. But if Japan doesn't surrender, we would have kept at it. And if it had been decided to wage tactical nuclear warfare in support of an invasion, there would have been no shortage of munitions.
 
Think just how money and manhours went into the first three bombs. And you want to use them as tactical weapons? The investment demands strategic use.
 
But the horrible aspects of such a battle, with Allied troops hopefully not but possibly themselves blasted by the bomb, then having to advance directly into the just-nuked blast zone, no doubt to have to dig in just beyond it--or in the middle of it!:eek: against more Japanese defenders, all in the service of an invasion expected to be a major bloodbath on both sides--well, it is a good thing the Japanese surrendered before it came to that.

Nuclear airbursts produce negligible radiation danger after the initial fireball is gone.
 
But what is the danger of occupying the area that has been nuked?

Not something I'd want to risk, with the benefit of hindsight.

It depends on the weather and the height of burst. A low-yield air-burst on a clear day, if you don't get unlucky, the radiation should be gone by the time the fires die off. All the fallout particulates get blown up into the upper atmosphere, where it takes days (weeks?) before they fall back to the surface. A surface-burst, or if it's raining, that's a different matter.

Does anyone know if they were planning air- or ground-bursts for the invasion? Historically, ground-bursts have been considered preferable for tactical uses, since tanks and trenches are surprisingly effective protection against blast from low-yield air-bursts. But I don't know if they were thinking along those lines yet, or if they knew how bad the fallout from a surface-burst would be.
 
Because the invasion never took place?

Besides, if you have a weapon that can be used stategically, causing the other guy to surrender, or tactically to shorten the fighting a bit, why on earth would anyone even consider the latter. It would be even stupider than most wwii decisions:p

Seriously, the only way theyd be used tactically is if they had already been used strategically, and you STILL needed to keep fighting.
 
But what is the danger of occupying the area that has been nuked?

Not something I'd want to risk, with the benefit of hindsight.

Agreed, I believe many Allied formations would have been advancing in only 48 hours after the detonations. I'm no nuclear expert but that doesn't sound good...
 
But how many 'nuclear experts' were there in September 1945? Most of the effects were unknown and there was little reluctance in taking chances. After all there was a war on.
 
But how many 'nuclear experts' were there in September 1945? Most of the effects were unknown and there was little reluctance in taking chances. After all there was a war on.

Thus the comment being "with the benefit of hindsight".

We do know that it could potentially be horrendous. For all they knew, this was just one hell of a bomb, without any especially lethal lingering effects beyond the unspeakable carnage on initial explosion.

I have a half-memory of reading something where they might have known about radiation, but believed that anyone who might be affected by it would have been in the "killed instantly" radius, or something along those lines.

But still. This is pretty disturbing.
 
Thus the comment being "with the benefit of hindsight".

We do know that it could potentially be horrendous. For all they knew, this was just one hell of a bomb, without any especially lethal lingering effects beyond the unspeakable carnage on initial explosion.

I have a half-memory of reading something where they might have known about radiation, but believed that anyone who might be affected by it would have been in the "killed instantly" radius, or something along those lines.

But still. This is pretty disturbing.

We need to distinguish between the initial pulse and the lingering fallout. They knew about the pulse, but they figured anyone close enough to be effected would be dead. They'd know enough to keep troops far enough away to ensure they wouldn't be sickened by that.

For the lingering fallout, it's not clear to me how much they knew. They knew it existed, but they figured that, with airbursts, it would be blown up into the upper atmosphere and be diluted and decay before it returned to Earth. They were correct in this assumption. It's not clear to me if they knew that groundbursts would leave lingering fallout, nor am I aware if their tactical plans envisioned air or ground bursts.

Moreover, while they had a good handle on how much radiation is needed to cause acute symptoms, they really didn't know much about the link between cancer and radiation. They knew there was one, but almost all of our reliable information about how much cancer is caused by how much radiation actually comes from studying the victims of the two atomic bombings, so any radiation safety standards they'd set regarding cancer would be essentially guesses. For that matter, we still know less than people realize about the link between radiation and cancer.

At the very least, they probably knew enough to issue lead elements of the invasion force with Geiger counters, and keep them clear of fallout severe enough to cause acute, immediate effects. What happens twenty years later is a different story.
 

CalBear

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Actually I took the actual stockpile and production from OTL, according to declassified U.S. records for the end of 1946 (Nine weapons) and doubled it to account for full out war production efforts. I was probably way generous, but still in the ball park. If I had gone straight OTL, there would have been, at most, two weapons in inventory after the proposed tactical use against the Kyushu defenses.

https://www.osti.gov/opennet/forms.jsp?formurl=document/press/pc26tab1.html
Are you using the 2 and a bit per month figure? Because that doesn't take into account the improvements being made to production and bomb design.

Los Alamos was actively pursuing levitated composite core designs, which would have been operational in the near future - Oppenheimer actually suggested breaking up Little Boy to make four composite bombs, but Groves preferred one bomb now to four bombs in a month. This would have radically improved their efficiency of using fissile material. Bomb design improvements would have allowed them to make 6 bombs per month using their existing fissile production rate. Production of fissiles was also increasing as they worked the kinks out of the Oak Ridge complex; combining the two would increase production to 10 bombs per month. Alternatively they could have produced a smaller number of higher-yield devices.

IOTL, the war ended and everybody went home, and it took a few more years before we started using composite cores. But if Japan doesn't surrender, we would have kept at it. And if it had been decided to wage tactical nuclear warfare in support of an invasion, there would have been no shortage of munitions.
 
Actually I took the actual stockpile and production from OTL, according to declassified U.S. records for the end of 1946 (Nine weapons) and doubled it to account for full out war production efforts. I was probably way generous, but still in the ball park. If I had gone straight OTL, there would have been, at most, two weapons in inventory after the proposed tactical use against the Kyushu defenses.

https://www.osti.gov/opennet/forms.jsp?formurl=document/press/pc26tab1.html

That's because they practically shut down the Manhattan Project when the war ended, including shutting down or reducing the power level of the Hanford reactors to protect them against neutron irradiation damage. If they'd kept the production running full-steam, they'd have ten a month by early 1946. Source. (Note original source is fas.org, who know what they're talking about, but these guys are rehosting it as the original seems to have been taken down.) ETA: Another good source for the neutron irradiation damage, although it doesn't have production figures as they weren't declassified yet when it was written, is Hewlett and Anderson's The New World: A History of the US Atomic Energy Commission 1936-1946, which the DoE has put up on their Information Bridge server as a pdf.
 
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That's because they practically shut down the Manhattan Project when the war ended, including shutting down or reducing the power level of the Hanford reactors to protect them against neutron irradiation damage. If they'd kept the production running full-steam, they'd have ten a month by early 1946. Source. (Note original source is fas.org, who know what they're talking about, but these guys are rehosting it as the original seems to have been taken down.) ETA: Another good source for the neutron irradiation damage, although it doesn't have production figures as they weren't declassified yet when it was written, is Hewlett and Anderson's The New World: A History of the US Atomic Energy Commission 1936-1946, which the DoE has put up on their Information Bridge server as a pdf.

That is what i was aiming for. If the war had continued, production of nuclear bombs had kept going at full speed.
 
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