Posts Tagged ‘1940s’

Meditations

Tokyo vs. Hiroshima

Monday, September 22nd, 2014

How many people would have died if an atomic bomb had been dropped on Tokyo in early 1945, instead of firebombs? Before you accuse me of excessive obsession with morbidity (as one anonymous e-mailer recently did), let me explain to you how I came to ask myself this question, and what the consequences of the answer are.

Before the dropping of the atomic bomb on Hiroshima and Nagasaki, there was the burning of Tokyo. Operation Meetinghouse, the early March 1945 raid on Tokyo that involved over 330 B-29s dropping incendiary bombs from low-altitude at night, killed roughly 100,000 people, and may have injured and made homeless an order of magnitude more. As with all statistics on the damage caused by strategic bombing during World War II, there are debatable points and methodologies, but most people accept that the bombing of Tokyo probably had at least as many deaths as the Hiroshima bombing raid, and probably more. It is sometimes listed as the most single deadly air raid of all time as a consequence.

The ruins of 1945: Tokyo, left, and Hiroshima, right.

The ruins of 1945: Tokyo, left, and Hiroshima, right.

So it is understandable that many people, including myself, point to Tokyo whenever people want to talk about Hiroshima and Nagasaki. You can’t see the atomic bombings in isolation. The practice of targeting civilian areas with massively destructive aerial bombing had already been done before. And to some, the atomic bombs were just a refinement of the art of area bombing — a more efficient means to accomplish the same ends.1

However, there are a few points that I fear get missed in that kind of equivalence. I certainly agree that the philosophy of bombing used at Hiroshima and Nagasaki wasn’t a new one. Indeed, the experience of firebombing gave a lot of guidance to the question of nuclear targeting. The goals were similar, though the people planning the atomic bombs emphasized the raw terror that they hoped such a spectacle would inspire.

But I depart from the standard comparison in two places. The first is the idea that since the atomic bombings were not original in targeting civilians, then they do not present a moral or ethical question. As I’ve written about before, I think the question of morality gets more problematic. If the atomic bombings were one-off events, rare interventions to end the war, then it might (for some) be compelling to say that they were worth the price of crossing over some kind of line regarding the deliberate burning of civilians to death en masse. But if they were instead the continuation of a well-established policy of burning civilians to death en masse, then the moral question gets much broader. The question changes from, Was it morally justified to commit a civilian massacre two times?, to Was it morally justified to make civilian massacre a standard means of fighting the war? 

I want to state explicitly that I don’t think, and I don’t want my phrasing to imply, that the answer to the above is necessarily an unequivocal “no.” There are certainly many moral frameworks that can allow for massacres (e.g. ends-justify-the-means). But I prefer to not dress this sort of thing up in euphemisms, whether we think it justified or not.  Massacre means to deliberately and indiscriminately kill people. That is what you get when you bomb densely-populated cities with weapons that cannot distinguish between civilians and members of the military. Incendiary raids and atomic bombs certainly fall in this category, whether one thinks that the circumstances required them or not.

Japanese cities destroyed by strategic bombing in World War II. More information about this map here.

Japanese cities destroyed by strategic bombing in World War II. More information about this map here.

The second place I depart is a technical one. There are several important differences between the effects of firebombing and atomic bombing. They are not, even in the case of the bombing of Japan, strictly equivalent from the point of view of their effects or their outcomes.

The Tokyo firebombing raid was a relatively slow (compared to an atomic bomb), massively-distributed attack. The Tokyo raid involved hundreds of B-29 bombers arriving and attacking over the course of several hours. Such massive groups of B-29s could be heard and tracked from a considerable distance. They spread their bombs over a large area of the city, with the goal of creating a mass conflagration that would be impossible to control. They could be fought against with interceptors and anti-aircraft guns; air-raid alarms could be sounded; civilians could flee to shelter, or outside of the city itself.  This is not to imply that any of these strategies were necessarily effective, and it does not necessarily make firebombing raids any more “humane.” But it does change the outcome quite a bit, when compared to an atomic bomb attack.

The atomic bombing raids of Hiroshima and Nagasaki were fast, near-instantaneous attacks. They involved a single B-29 weather plane in advance, and then two or three B-29s approaching the city, one with the bomb itself. This means that effective air-raid warning was minimal, because it was not possible to distinguish an atomic bomb attack from a reconnaissance or weather flight, all of which were common by that late stage in the war. (And obviously any hope of detecting an atomic bomb attack was impossible prior to Hiroshima.)

Drawing by Goro Kiyoyoshi of his memories of the Hiroshima attack. "I got on a streetcar of the Kabe line about 8:10 AM. The door was open and I was standing there. As I heard the starting bell ring, I saw a silver flash and heard an explosion over the platform on which l had just walked. Next moment everything went dark. Instinctively I jumped down to the track and braced myself against it. Putting a handkerchief to my mouth, I covered my eyes and ears with my hands."

Drawing by Goro Kiyoyoshi of his memories of the Hiroshima attack. “I got on a streetcar of the Kabe line about 8:10 AM. The door was open and I was standing there. As I heard the starting bell ring, I saw a silver flash and heard an explosion over the platform on which l had just walked. Next moment everything went dark. Instinctively I jumped down to the track and braced myself against it. Putting a handkerchief to my mouth, I covered my eyes and ears with my hands.” From Unforgettable Fire: Drawings by Atomic Bomb Survivors (1977).

The primary acute effects of the atomic bombs were blast and thermal radiation. The former travels at the speed of sound, the latter significantly faster. (The rays are transmitted at more or less the speed of light, but the intensity and duration of the thermal pulse is a more complex phenomena and unfolds over the course of several seconds.) The blast knocks down buildings. The thermal radiation heats and burns. Both contribute to the starting of fires — the thermal radiation directly (for certain materials), the blast wave indirectly by knocking over flammable materials, stoves, candles, etc. After Hiroshima there was a significant firestorm, as with incendiary bombing, but there was not after Nagasaki. There was no effective preparation for such an attack — perhaps if they had the foresight of some later Civil Defense techniques, some lives could have been saved (different shelter types did affect the fatality rates significantly, even close in to the zero point), but obviously this was not quite in the cards during the war itself, when the atomic bomb was such a novelty. There was no time for shelters, no time to flee the city, no time even for real comprehension of what was happening — a bright light followed by a crushing blast, followed by fire. For those who survived the blast and fire, there were radiation effects, if they were with a few kilometers of the epicenter. This could range from acute radiation sickness and death with several weeks, to an increased cancer risk over the course of their lives.

Are the atomic bomb effects significantly different from firebombing to warrant putting them into different ethical or moral categories? One could argue the point either way. I tend to think that they are both pretty terrible forms of suffering, but they are not identical. In many ways the atomic bombing effects were significantly worse for the people living in the target cities — all of the suffering of firebombing accelerated, with a few new terrors added into the mix, and with less warning.

Table from a 1963 Office of Civil Defense report, "Survey of the Thermal Threat of Nuclear Weapons," by Jack C. Rogers and T. Miller. These numbers are not necessarily authoritative, but they give some indication of the relative mortality rates differences I am talking about.

Table from a 1963 Office of Civil Defense report, “Survey of the Thermal Threat of Nuclear Weapons,” by Jack C. Rogers and T. Miller. These numbers are not necessarily authoritative, but lay out the situation well: atomic bombs have much higher mortality and casualty rates per square mile than firebombing, but destroy proportionally smaller amounts of area.

But the equivalence argument also misses some important differences in how deadly the atomic bombs were. The firebombing of Tokyo did, indeed, kill the most people of any air raid in history — from 80,000 to over 100,000 dead in a single raid. But the city of Tokyo had some 5 million people living in it. In the areas targeted, there were 1.5 million people living. So that means that it killed no more than 2% of the total population of the city, and no more than 7% of the people who lived in the targeted areas. The bombing of Hiroshima killed between 90,000 and 160,000 people in a city of 345,000 or so. So that is a fatality rate of 26-46%, depending on whose fatality estimates you go with. The bombing of Nagasaki killed between 39,000 to 80,000 people in a city of 260,000 people or so. So that is a fatality rate of 15-30%.

So to put it another way, the Hiroshima bombing was around 5 times more deadly than the Tokyo raid per capita, and the Nagasaki bombing was maybe 4 times more deadly. The total number dead is similar in all three cases, but the total number of people possible to kill in Tokyo was much higher than the number of people in Hiroshima and Nagasaki.

This isn’t the whole story, though. There is a subtle technical difference mixed in here. Firebombing on par with the Tokyo raid spread a moderate chance of death over a large area. The atomic bombs dropped in World War II spread a very high chance of death over a relatively small area. So depending on the target in question, the difference in fatalities might or might not matter. The Hiroshima bomb was perfectly capable of killing something like half of the city — but it was a pretty small city, compared to Tokyo. Tokyo has areas of incredibly high density, but also large areas of relatively moderate to low density.

So why does this matter? From an ethical standpoint, I’m not sure it does. The targeting of civilians for mass destruction seems to be the core ethical issue, whether you do this by means of fire, neutrons, or toxic gas. But I do think we end up underestimating the effects of the atomic bombs if we see them as exactly equivalent to firebombs. There is an error in seeing the atomic bombs as just an expeditious form of firebombing — it both overstates the deadliness of firebombing while understating the deadliness of atomic bombs.

This map gives a rough indication of the methodology used to construct the casualty estimates for a Little Boy bomb targeted on World War II Tokyo. Percentages are expected average fatality rates. The actual method used (see below) used many more gradations of difference. One can see, though, the way in which the most intense of the effects of the atomic bomb are highly localized relative to the total size of Tokyo.

This map gives a rough indication of the methodology used to construct the casualty estimates for a Little Boy bomb targeted on World War II Tokyo. Percentages are expected average fatality rates. The actual method used (see below) used many more gradations of difference. One can see, though, the way in which the most intense of the effects of the atomic bomb are highly localized relative to the total size of Tokyo. The underlying population density map of Tokyo comes from the very useful Japanairraids.org.

All of this is what led me to the question I opened with: What if, in some hypothetical alternative universe, instead of launching a firebombing raid in early March 1945, the US was able to drop the Little Boy atomic bomb onto Tokyo? What would the casualties have been for that raid?

Obviously an exact answer is not possible. But we do have population density maps of Tokyo, and we do have records on the relationship between distance from “ground zero” and percentage of population killed. There are lots of uncertainties, here, regarding the types of buildings, the differences in geography, and other things that are hard to estimate. But let’s do a rough estimation.

If we transpose the effects of Hiroshima — a 15 kiloton bomb detonated around 1,968 feet above the ground — to the population densities of Tokyo, what is the result? I don’t want to clog up the blog post with a detailed explanation of the methodology I’ve used, so I’m putting it at the end with the footnotes. The basic gist of it was this: I took a population density map of Tokyo from 1940, divided the different density areas into different layers in Photoshop, then selected radii based on bomb effects and did pixel counting. I used all of this to come up with rough minimum-maximum estimates of how many people lived in areas at different regions from the bomb blast, and then multiplied those population counts against known average fatality/casualty rate data taken from Hiroshima.

I looked at two ground zeros, to further emphasize the intense locality of a Hiroshima-sized atomic bomb attack (compared to a firebombing raid). If targeted on the moderately-dense Honjo area (which is more or less the center of the firebombing attack), one could roughly expect there to be between 213,000 and 344,000 fatalities, and between 442,000 and 686,000 injuries. This is the ground zero shown in the above image. If you move it north-west by only 1 km, though, to the more densely populated Asakusa area, the numbers change to 267,000 to 381,000 dead and 459,000 to 753,000 injured.

So if the Hiroshima bomb had been dropped on Tokyo, it probably would have destroyed less area than the March 1945 Tokyo firebombings — something like 5 square miles, compared to the 15 square miles destroyed by firebombing. However it would have killed between two and four times as many people who died in the firebombings, and injured possibly fewer or the same amount of people.

These numbers seem roughly plausible to me, even given all of the uncertainties involved, and they align with the rough guess one would make from the relative area destruction and casualty rates cited earlier. It is of note that the shifting of an atomic bomb’s aiming point can increase total casualties by several tens of thousands of people in a city the density of Tokyo; firebombing is probably not quite as dependent on any given aiming point, given how much lower the accuracy was.

Finally, it is worth noting that the Tokyo firebombing was much more fatal than most of the other firebombing raids. As the first low-altitude, massed night B-29 incendiary raid, against Japan’s highest-density city, it was especially fatal. Later raids killed, on average, orders of magnitudes less, both for the reasons given at the beginning (e.g. fleeing when you hear hundreds of B-29s in the distance), and because of much lower population densities. Had Hiroshima been firebombed, the fatalities would have certainly been much lower than the atomic bombings, because the Tokyo case is in fact an anomalously high one.

Atomic bombings may be ethically no better or worse than firebombing raids like Tokyo, but to regard them as simply an expedient form of firebombing misses a key point about their relative deadliness: If you have to pick, and you get to pick, one should choose to be firebombed, not atomic bombed — unless you know exactly where the bombs are going to go off.

Click for the full casualty calculation methodology.

Notes
  1. On this, see esp. Michael Gordin’s Five Days in August, and, perhaps,  my review of it. []
Redactions

General Groves’ secret history

Friday, September 5th, 2014

The first history of the Manhattan Project that was ever published was the famous Smyth Report, which was made public just three days after the bombing of Nagasaki. But the heavily-redacted Smyth Report understandably left a lot out, even if it did give a good general overview of the work that had been done to make the bomb. Deep within the secret files of the Manhattan Project, though, was another, classified history of the atomic bomb. This was General Leslie Groves’ Manhattan District History. This wasn’t a history that Groves ever intended to publish — it was an internal record-keeping system for someone who knew that over the course of his life, he (and others) would need to be able to occasionally look up information about the decisions made during the making of the atomic bomb, and that wading through the thousands of miscellaneous papers associated with the project wouldn’t cut it.

Manhattan District History - Book 2 - Vol 5 - cover

Groves’ concern with documentation warms this historian’s heart, but it’s worth noting that he wasn’t making this for posterity. Groves repeatedly emphasized both during the project and afterwards that he was afraid of being challenged after the fact. With the great secrecy of the Manhattan Project, and its “black” budget, high priority rating, and its lack of tolerance for any external interference, came a great responsibility. Groves knew that he had made enemies and was doing controversial things. There was a chance, even if everything worked correctly (and help him if it didn’t!), that all of his actions would land him in front of Congress, repeatedly testifying about whether he made bad decisions, abused public trust, and wasted money. And if he was asked, years later, about the work of one part of the project, how would he know how to answer? Better to have a record of decisions put into one place, should he need to look it up later, and before all of the scientists scattered to the wind in the postwar. He might also have been thinking about the memoir he would someday write: his 1962 book, Now it Can Be Told, clearly leans heavily on his secret history in some places.

Groves didn’t write the thing himself, of course. Despite his reputation for micromanagement, he had his limits. Instead, the overall project was managed by an editor, Gavin Hadden, a civil employee for the Army Corps of Engineers. Individual chapters and sections were written by people who had worked in the various divisions in question. Unlike the Smyth Report, the history chapters were not necessarily written near-contemporaneously with the work — most of the work appears to have been started after the war ended, some parts appear to have not been finished until 1948 or so.

General Groves not amused

In early August 1945 — before the bombs had been dropped — a guide outlining the precise goals and form of the history was finalized. It explained that:

Tho purpose of the history is to serve as a source of historical information for War Department officials and other authorized individuals. Accordingly, the viewpoint of the writer should be that of General Groves and the reader should be considered as a layman without any specialized knowledge of the subject who may be critical of the Department or the project.

Which is remarkably blunt: write as if Groves himself was saying these things (because someday he might!), and write as if the reader is someone looking for something to criticize. Later the guide gives some specific examples on how to spin problematic things, like the chafing effect of secrecy:

For example, the rigid security restrictions of the project in many cases necessitated the adoption of unusual measures in the attainment of a local objective but the maintenance of security has been recognized throughout as an absolute necessity. Consequently, instead of a statement such as, “This work was impeded by the rigid security regulations of the District,” a statement such as, “The necessity of guarding the security of the project required that operations be carried on in — etc.” would be more accurate.1

This was the history that Groves grabbed whenever he did get hauled in front of Congress in the postwar (which happened less than he had feared, but it still happened). This was the history that the Atomic Energy Commission relied upon whenever it needed to find out what its predecessor agencies had done. It was a useful document to have around, because it contains all manner of statistics, technical details, legal details, and references to other documents in the archive.

"Dante's Inferno: A Pocket Mural" by Louis C. Anderson, a rather wonderful and odd drawing of the Calutron process. From Manhattan District History, Book 5, "Electromagnetic Project," Volume 6.

“Dante’s Inferno: A Pocket Mural” by Louis C. Anderson, a rather wonderful and odd drawing of the Calutron process. From Manhattan District History, Book 5, “Electromagnetic Project,” Volume 6.

The Manhattan District History became partially available to the general public in 1977, when a partial version of it was made available on microfilm through the National Archives and University Publications of America as Manhattan Project: Official History and Documents. The Center for Research Libraries has a digital version that you can download if you are part of a university that is affiliated with them (though its quality is sometimes unreadable), and I’ve had a digital copy for a long time now as a result.2 The 1977 microfilm version was missing several important volumes, however, including the entire book on the gaseous diffusion project, a volume on the acquisition of uranium ore, and many technical volumes and chapters about the work done at Los Alamos. All of this was listed as “Restricted” in the guide that accompanied the 1977 version.3

I was talking with Bill Burr of the National Security Archive sometime in early 2013 and it occurred to me that it might be possible to file a Freedom of Information Act request for the rest of these volumes, and that this might be something that his archive would want to do. I helped him put together a request for the missing volumes, which he filed. The Department of Energy got back pretty promptly, telling Bill that they were already beginning to declassify these chapters and would eventually put them online.

Manhattan Project uranium production flow diagram, from book 7, "Feed materials."

Manhattan Project uranium production flow diagram, from Manhattan District History, Book 7, “Feed materials.”

The DOE started to release them in chunks in the summer of 2013, and got the last files up this most recent summer. You can download each of the chapters individually on their website, but their file names are such that they won’t automatically sort in a sensible way in your file system, and they are not full-text searchable. The newly-released files have their issues — a healthy dose of redaction (and one wonders how valuable that still is, all these years — and proliferations — later), and some of the images have been run through a processor that has made them extremely muddy to the point of illegibility (lots of JPEG artifacts). But don’t get me started on that. (The number of corrupted PDFs on the NNSA’s FOIA website is pretty ridiculous for an agency that manages nuclear weapons.) Still, it’s much better than the microfilm, if only because it is rapidly accessible.

But you don’t need to do that. I’ve downloaded them all, run them through a OCR program so they are searchable, and gave them sortable filenames. Why? Because I want people — you — to be able to use these (and I do not trust the government to keep this kind of thing online). They’ve still got loads of deletions, especially in the Los Alamos and diffusion sections, and the pro-Groves bent to things is so heavy-handed it’s hilarious at times. And they are not all necessarily accurate, of course. I have found versions of chapters that were heavily marked up by someone who was close to the matter, who thought there were lots of errors. In the volumes I’ve gone the closest over in my own research (e.g. the “Patents” volume), I definitely found some places that I thought they got it a little wrong. But all of this aside, they are incredibly valuable, important volumes nonetheless, and I keep finding all sorts of unexpected gems in them.

You can download all of the 79 PDF files in one big ZIP archive on Archive.org. WARNING: the ZIP file is 760MB or so. You can also download the individual files below, if you don’t want them all at once.

Statistics on the ages of Los Alamos employees, from Ted Hall (19) to Niels Bohr (59). From Manhattan District History, Book 8.

Statistics on the ages of Los Alamos employees, May 1945, from the young spy, Ted Hall (19), to the old master, Niels Bohr (59). From Manhattan District History, Book 8.

What kinds of gems are hidden in these files? Among other things:

And a lot more. As you can see, I’ve drawn on this history before for blog and Twitter posts — I look through it all the time, because it offers such an interesting view into the Manhattan Project, and one that cuts through a lot of our standard narratives about how it worked. There are books and books worth of fodder in here, spread among some tens of thousands of pages. Who knows what might be hidden in there? Let’s shake things up a bit, and find something strange.


Below is the full file listing, with links to my OCR’d copies, hosted on Archive.org. Again, you can download all of them in one big ZIP file by clicking here, (760 MB) or pick them individually from below. Read the full post »

Notes
  1. E.H. Marsden, “Manhattan District History Preparation Guide,” (1 August 1945), copy in the Nuclear Testing Archive, Las Vegas, Nevada, accession number NV0727839. []
  2. In fact, I used portions of it — gasp! — on actual microfilm very early on my grad school career, when you still had to do that sort of thing. The volume on the patenting program was extremely useful when I wrote on Manhattan Project patent policies. []
  3. Some of the Los Alamos chapters were later published in redacted form as Project Y: The Los Alamos Story, in 1983. []
Meditations

The luck of Kokura

Friday, August 22nd, 2014

On the morning of August 9th, 1945, a B-29 bomber left the island of Tinian intending to drop an atomic bomb on the city of Kokura, the location of one of the largest arsenals still standing in Japan. On arriving at the target, the plane found it obscured by clouds. It turned south and went to its secondary target: Nagasaki. 

Supposedly, some in Japan still refer to the “luck of Kokura” in reference to this time in which some bad weather saved the lives of tens of thousands of people there. But what really happened that morning? Was it bad weather, or something else, that obscured, and thus saved, Kokura? 

Surprisingly, there are actually a few different theories floating around, and the uncertainty over the matter is generally not realized or acknowledged.

Model of the Kokura arsenal made for targeting purposes, ca. 1945. North is in the lower-right hand corner. Source: USAAF photos, via Fold3.com.

Model of the Kokura arsenal made for targeting purposes, ca. 1945. North is in the lower-right hand corner. Source: USAAF photos, via Fold3.com.

But first, let’s review the basics of the mission. The Kokura/Nagasaki mission (dubbed CENTERBOARD II), as with the Hiroshima mission before it (CENTERBOARD I), did not involve the bomber flying on its lonesome to the target, as is sometimes imagined. There were a total of six planes involved in the mission, all B-29 bombers. One of them was the strike plane that carried the Fat Man implosion bomb (Bockscar).1  Two other planes (The Great Artiste and Big Stink) were instrument and observation planes. One other plane was a “standby” plane (Full House) that was to serve as backup if the three bombing planes ran into air resistance — because they didn’t, it instead flew back to Iwo Jima instead of on to the target after a rendezvous with the bombing plane. Lastly, there were two weather planes that flew out in advance, one to Nagasaki (the Laggin’ Dragon), the other to Kokura (the Enola Gay, the same plane that had dropped the atomic bomb on Hiroshima a few days earlier, but with a different crew). The weather planes would check out bombing conditions and then circle back, helping the bomber plane determine whether the primary or secondary target would be used. Niigata, a third atomic bombing target, was not considered on this mission because of its great geographical distance from Kokura and Nagasaki.

Bockscar was being piloted by Major Charles Sweeney. It had taken off from the island of Tinian at 3:47am, Tinian time. They had arrived at a rendezvous point at Yakushima Island around 9:15am. It rendezvoused with one of the other B-29s (the instrument plane), but did not spot the other one (the photo plane). At 9:50am, the pilot of Bockscar, Charles Sweeney, gave up and continued on to Kokura, having waited some 30 minutes longer than he was supposed to. At 10:44am, they arrived at Kokura. The flight log records that “Target was obscured by heavy ground haze and smoke.” A crew member of Bockscar rated it as “7/10 clouds coverage – Bomb must be dropped visually but I don’t think our chances are very good.”2

Three bombing runs on Kokura were attempted, but “at no time was the aiming point seen,” as the flight log recorded. Visual bombing had been made a mandatory requirement (they did not trust the accuracy of radar-assisted bombing), so this made Kokura a failed mission. Since Bockscar had limited fuel, Sweeney decided to continue on to the secondary target, Nagasaki. They arrived at Nagasaki at 11:50am, which they also found obscured by smoke and clouds, to the degree that they made the target approach entirely by radar. Right at the last possible moment, the clouds parted just enough for the bombardier to site the target and drop the bomb. (It missed the intended target by a significant margin.) Bockscar circled the target once and then, at 12:05pm, took off for Okinawa, and from there, after refueling, Tinian.

Care about the details of the Hiroshima and Nagasaki bombings? Get this book.

Care about the details of the Hiroshima and Nagasaki bombings? Get John’s book. I’m not just saying that because he says nice things about my blog, either.

An aside: For anyone interested in the nitty-gritty details of the Hiroshima and Nagasaki missions, my go-to reference these days is John Coster-Mullen’s Atom Bombs: The Top Secret Insider Story of Little Boy and Fat Man. I first got a copy of John’s book in 2006 or so. John sent me a new copy a few months ago, and I have been impressed with how much new material he has added over the last 8 years. (And I have managed to find a few useful things for him over the years, which have made it into his book as well — duly credited!) If you’re interested in the history of the Manhattan Project, you can’t not have a copy of John’s book… and if your copy is over 5 years old, considered getting an updated edition! All of these little details about times and planes and whatnot come from John’s book.

So what caused the “heavy ground haze and smoke”?

Theory #1: Bad weather

The most common explanation for the obscuring of Kokura is one of weather. It seems to me to be a valid possibility, but let’s pick it apart a bit.

As noted, the Enola Gay had flown ahead to Kokura to scope out the visual conditions. They had radioed back that the visibility was “3/10 low clouds, no intermediate or high clouds, and forecast of improving conditions.”3 That was a favorable-enough weather report that Kokura, the primary target, was chosen as the first run. Upon arriving, however, Bockscar found the weather conditions were now 7/10 — too obscured to bomb. Is this plausible?

Summer weather patterns in Japan, map made in early 1945. Not great for bombing. Source: Produced for the USAAF's IMPACT magazine, high-res version via Fold3.com.

Summer weather patterns in Japan, map made in early 1945. Not great for bombing. Source: Produced for the USAAF’s IMPACT magazine, high-res version via Fold3.com. There is another wonderful map for winter weather as well.

General Groves, in his 1964 memoir, suggests that it might have been the case that the change in weather conditions was simply a matter of how much time had passed between the forecast and arrival of Bockscar. The strike plane was, as noted, delayed by around half an hour. Groves also implies that there may have been a difference between how visual the target was at an angle — how a bombardier sees it — and how it looks from straight above — how a weather plane sees it). He concludes that the reasons for the haze were “never determined.”4

On the face of it, it’s hard to know whether such a rapid change in visibility is possible through entirely natural causes. In some parts of the world, the weather can be very volatile. Japan is one of these parts of the world, especially around the late fall. The variability of Japanese weather conditions was something that the US Army Air Forces knew very well, and was one of the bane of their bombing plans. It was a major issue in the atomic bombing discussions as well since very early on. At the first Target Committee meeting in April 1945, weather was a major point of discussion:

…it was pointed out that the months in which the initial mission will be run constitute the worst weather months of Japan. [...] Dennison pointed out that all weather maps indicated that there were only an average of 6 good bombing days in August and that of those 6 days a conservative estimate would probably result in safely predicting that we would have 3 good days in the month of August but these 3 good days could not be positively predicted in advance of more than 48 hours. 

Elsewhere in the memo it remarks that “3/10ths or less” cloud coverage was considered acceptable for visual bombing. It also notes that “only once in 6 years have there ever been 2 successive good visual bombing days of Tokyo,” which gives some indication of the weather’s variability.

Weather from the nearby city of Shimonoseki for August 8-9, 1945. Click to enlarge, or click here for the Excel file. Source: Japanese M

Weather from the nearby city of Shimonoseki for August 8-9, 1945. Click to enlarge, or click here for the Excel file. Source: Courtesy of the Japanese Meteorological Agency.

So it doesn’t seem impossible that it could have just been according to the weather, though the big difference between the conditions reported by the weather plane and the observed conditions by the strike plane seem, on the face of it, beyond what a half hour’s delay would accomplish. One question I don’t have the answer for is when the weather plane radioed those conditions back. In the case of the Hiroshima run, the weather plane was only 30 minutes earlier than the strike plane. If we assume that was a similar attempt on the second mission, it would mean that the strike plane was reaching the target over an hour after the weather plane had seen it, which could be a significant-enough delay for a serious change in visibility. (And another possibility is that the weather plane could have been, for whatever reason, incorrect — either at the wrong place or had its message garbled.)

There aren’t good weather records from this period, at least none I have seen. The closest site for state weather recording was in Shimonoseki, some 7 miles / 11 km northeast of Kokura. I asked the Japan Meteorological Agency for any records they had from that period and they sent me the above data.5 It is not especially helpful towards answering this question that I can see, but I’m not a meteorologist in the slightest. For me, the big take-away from the data is that it could go from totally clear to totally obscured over the course of an hour, which at least supports the plausibility of the weather theory.

Theory #2: Smoke from firebombing

One of the other causes put forward is that the “smoke and haze” seen over Kokura was actually a result of nearby firebombing. On August 8th, 1945, the 20th AF had sent 221 B-29s to the nearby city of Yahata (Yawata) to drop incendiary bombs.6 Yahata had been bombed several times during the war. It was, in fact, the site of the first B-29 attack on the Japanese homeland in June 1944, and indeed the first bombing attack against the Japanese homeland at all since the Doolittle raid. It had been bombed again in August 1944. The USAAF considered Yahata to be the largest steel producing center in the country, and dubbed it “the Pittsburgh of Japan.” It was the last Japanese city to be hit by a massive B-29 raid, a “night burn job” as a USAAF writer put it, and it was considered “leftover business” that had been scheduled to take place much earlier but delayed because of bad weather.7

Yahata/Yawata target map, March 1945. Kokura arsenal is visible to the east. Source: JapanAirRaids.org. Click here for the uncropped, unadjusted version.

Yahata/Yawata target map, March 1945. Kokura arsenal is visible to the east. Source: JapanAirRaids.org. Click here for the uncropped, unadjusted version.

The weather at Yahata had been 4/10 clouds over the target, but this didn’t matter for B-29 firebombing raids, because accuracy was not as big a concern as with the atomic bombs. The planes had arrived at Yahata around noontime. I’ve found very little in terms of documentation about how much of Yahata was burned out with this raid — perhaps because it was so late in the war, many of the traditional sources for information about incendiary bombing results (especially those contained on the invaluable website JapanAirRaids.org) essentially omit any discussion of this final big raid.

Could the bombing of Yahata have been the cause of the smoke that obscured Kokura? It doesn’t seem impossible, but it seems to me to be somewhat unlikely.

Approximate areas of interest in Yahata and Kokura, as seen on Google Earth today.

Approximate areas of interest in Yahata and Kokura, as seen on Google Earth today.

Bockscar was flying over Kokura just a little under 24 hours after the Yahata raid began. Incendiary raids did produce extreme amounts of smoke cover, as other photographic evidence indicates clearly. Yahata was only around 6 miles / 9 km west of Kokura (and their proximity is emphasized by the fact that both are today just considered wards of a larger city, Kitakyushu).

It seems odd that the Yahata smoke would have caught them off-guard. Wouldn’t the weather plane have noticed that there was smoke over Yahata rolling towards Kokura, or at least threatening it? Yahata is close enough that at the 30,000 feet or so that a weather plane would be flying over Kokura, all they would have to do is glance in its direction to see if there was heavy cloud cover. (One can easily replicate this experience with Google Earth if one chooses.) Could the smoke cloud have been lagged behind by just the amount of time that the weather plane wouldn’t see it, then rush ahead to obscure Kokura an hour later? Could the smoke have gone from non-obscuring to obscuring in just an hour? At the wind speeds measured at Shimonoseki (around 2-12 mph), it doesn’t strike me as super likely, but I’m not an expert in this kind of thing.

Theory #3: Japanese smokescreen

One last, more obscure theory. I first read of this in John Coster-Mullen’s book. I will quote him here:

When [Bockscar] finally arrived at 10:44 AM, smoke and industrial haze had obscured Kokura. Yahata had been firebombed by over 200 of LeMay’s B-29’s the previous day and the smoke had drifted over nearby Kokura. There was also a POW camp right next door to the main downtown power plan. An American prisoner in this camp reported later the Japanese had installed a large pipe that went from the power plant down to the river. He stated that whenever B-29’s were sighted over Kokura, the steam in the plant was diverted through this pipe and into the river. This created enormous condensation clouds that also helped to obscure the city.

John himself seems to have interviewed the POW camp survivor in question, and notes in a footnote that he thinks this was the first time this claim had surfaced in print. I certainly hadn’t seen it anywhere prior to John’s book. John asked Commander Ashworth about this in 1995, and Ashworth replied that this seemed possible, and added “if the Japanese really did that, then they were damn clever!”

German smokescreen use at Wilhelmshaven in June 1943. Caption: "Despite a smoke screen, 168 B-17s of the Eighth Air Force attacked Wilhelmshaven on 11 June. There are three lines of generators to windward of the area covered when the wind is in the north, as it was in this case. Generator boats are at the upper left. Despite the extent of the smoke screen hits are observed inside the circle..." Source: USAAAF IMPACT magazine, vol. 1, No. 5, August 1945, page 18.

German smokescreen use at Wilhelmshaven in June 1943. Caption: “Despite a smoke screen, 168 B-17s of the Eighth Air Force attacked Wilhelmshaven on 11 June. There are three lines of generators to windward of the area covered when the wind is in the north, as it was in this case. Generator boats are at the upper left. Despite the extent of the smoke screen hits are observed inside the circle…” Source: USAAAF IMPACT magazine, vol. 1, No. 5, August 1943, page 18.

A few weeks ago, there was a story carried by Japanese newspapers along these lines:

As the 69th anniversary of the Nagasaki atomic bombing approaches, a former mill worker in the present-day city of Kitakyushu, Fukuoka Prefecture, spoke about his untold story on how he burned coal tar to block the view of U.S. aircraft as they were about to drop the A-bomb on the city. … Of the three workers, Oita resident Satoru Miyashiro, 85, who worked at a can factory in the steel mill at around the end of the war said he burned coal tar to lay a smoke screen on Aug. 9, 1945. … Miyashiro said about two days before the Nagasaki attack Yawata steel workers learned that Hiroshima had been wiped out by the “new bomb” from their colleagues who had come back to Yawata via Hiroshima. He thought the next target would be his city as there were arms factories located in the area.

Note that this isn’t quite the same thing — this is someone in Yahata who was burning coal tar after hearing an air raid drill, and the smoke going downwind (east) to Kokura. I find it a little odd that the worker in question doesn’t mention that Yahata itself was firebombed less than a day before he decided to do this.

Are either of these theories plausible? In terms of, could they have done these things — of course. Turning on an incinerator is not an implausible action, and neither is the steam cloud scenario.

But would this have reduced the visibility over Kokura from 3/10 to 7/10 in the time it took the strike plane to get there? I’m not an atmospheric scientist, so I wouldn’t want to hazard a strong position on this. One can presumably model both of these scenarios and see if either were possible. I would be extremely interested if anyone wanted to that!

Susquehanna Steam Electric Station — just an example of what a very large nuclear power plant can generate in terms of steam. It's a lot of steam. Could it obscure a city downwind of it from a B-29 bomber? Image source.

Susquehanna Steam Electric Station — just an example of what a very large nuclear power plant can generate in terms of steam. It’s a lot of steam. Could it obscure a city downwind of it from a B-29 bomber? Image source.

My gut thought is that they were not super likely to be wholly responsible for the cloud cover. If it had been steam from a single plant, I suspect someone on Bockscar would have noted it as such. We have lots of experience with steam-generating power plants — think of the clouds created by nuclear cooling towers. They certainly can put out a lot of steam. Would it be enough to block off the entire city? I’m kind of dubious.

What about the coal tar possibility? I’m especially dubious that this would have been enough. Setting up honest-to-god smokescreen for an entire city is hard work, even if you are a professional. When the Germans wanted to protect individual places (like plants) from bombers they set up dozens to hundreds of smoke pots to do the job, or used multiple dedicated smoke generators. Some of the larger smokescreen images I have found clearly involve lots of smoke sources placed at good intervals upwind of the target they are meant to protect. So I don’t know.

On the other hand, if the smoke from Yahata was not from the firebombing but instead something deliberate, it would explain the time delay issue. If the wind was going due east at around 5 mph, that would in fact be perfect for putting a smoke cover over Kokura. So it has its merits as a theory.

Conclusion

There are narrative aspects of each theory that appeal, and each of them change what is meant by the “luck of Kokura.” If bad weather is what saved Kokura, then it becomes a metaphor for how serendipitously life and death are dealt out by the hands of fate. If it was smoke from the firebombing of Yahata, then it becomes an ironic story about the Army Air Forces’ zeal for destruction could become counterproductive. If it was the result of deliberate action on behalf of the Japanese, then it becomes something much more complicated, a story about how individual action may have led to the saving of some lives… and the dooming of others. It also would change the standard story of how defenseless the Japanese were against these weapons.

The bombing of Nagasaki. Original source. Slightly edited to improve foreground/background distinction.

Of course, what was lucky for Kokura was not so for Nagasaki.

Looking at these three options, I find the weather theory the easiest one to stomach. Japanese weather patterns were notoriously hard to predict and it was known as the worst season for bombing conditions. That they could change over an hour seems unsurprising to me, especially for a coastal city, where clouds can come and go which impressive rapidity (as someone who has lived in the Berkeley, Boston, and New York areas can attest). I like the irony of the Yahata story, but there are things that just don’t add up — I don’t see why the weather plane would not have mentioned it, and it seems implausible to me that it would take almost exactly 24 hours for the heavy cloud cover to have migrated a mere 5-10 miles. And for reasons indicated, I’m not sure I buy the smokescreen story — it would have been really difficult to pull off that degree of cloud cover reliably. It would have taken tremendous foresight and luck. And it is strange that this story would be “buried” for so long. This doesn’t mean that someone didn’t try it (I am emphatically not calling anyone a liar!). It just means that I’m not sure it would have worked even if they did try it.

A separate possibility is “all of the above.” Maybe the weather was bad. Maybe there was haze from the Yahata bombing. Maybe someone did try to release steam or smokescreen. Maybe all of these things occurred at once, making “the luck of Kokura” something that was the result of multiple causes. That would make Kokura extra lucky, I suppose, and not fit into any of the above pat narratives. And make Nagasaki extra un-lucky in turn.

In the end, it doesn’t really matter which of these things happened. The bare fact is that Kokura didn’t get bombed and Nagasaki did. But I find looking into these kinds of questions useful as a historian. Too often it is easy to take for granted that the explanations given in narrative works of history are “settled,” when really they are often resting on very thin evidence, thinner perhaps than the historian who writes them realizes. I don’t think we really know what happened at Kokura, and I’m not sure we ever truly will.

Notes
  1. Sometimes you see it as “Bock’s Car,” but it said “Bockscar” on the side of the B-29. This is one of those places where I say, “who cares?” but purists are concerned with this kind of detail. []
  2. Flight diary of Lt. Fred Olivi, quoted in Coster-Mullen’s book. []
  3. Bockscar flight log by Commander Frederick Ashworth, included in Norman F. Ramsey, “History of Project A,” (27 September 1945). A full of copy of Ramsey’s report is included in Coster-Mullen’s Atom Bombs book. []
  4. Leslie Groves, Now it Can Be Told, 345: “At Kokura, they found that visual bombing was not possible, although the weather plane had reported that it should be. Whether this unexpected condition was due to the time lag, or to the difference between an observer looking straight down and a bombardier looking at the target on a slant, was never determined.” []
  5. Here is the original Excel file they sent me. []
  6. Most US sources list the city as “Yawata,” but it apparently corresponds with what is today transliterated as the city of Yahata, in Fukoka prefecture, and there is an entirely different city known as Yawata in Kyoto Prefecture. The kanji is the same. Yahata has since been absorbed by Kitakyushu, along with Kokura. []
  7. Tom Prideaux, “Mission to Yawata, 7 Aug. 1945,” IMPACT, vol. 3, no. 9 (September-October 1945), 53. []
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The Kyoto misconception

Friday, August 8th, 2014

This week we talk again of the anniversaries of the atomic bombings of Hiroshima and Nagasaki. But if the military brass had its way in 1945, we would speak of Kyoto as well. Kyoto was spared because of a personal intervention: the US Secretary of War, Henry L. Stimson, did not think it should be bombed. This story has been told many times, often as an example of how thin a line there is between life and death, mercy and destruction. But there’s an angle to this story that I think has gone overlooked: how the debate about targeting Kyoto led President Truman to a crucial misunderstanding about the nature of the atomic bomb.

Toji pagoda, in Kyoto, today. Had the Little Boy bomb been dropped on Kyoto, it would have likely been destroyed, as it was less than 3,000 feet from the proposed "Ground Zero" point. Source: Wikimedia Commons.

Toji pagoda, in Kyoto, today. Had the Little Boy bomb been dropped on Kyoto, it would have likely been destroyed, as it was less than 3,000 feet from the proposed “Ground Zero” point. Source: Wikimedia Commons.

Let’s start from the beginning. The first concrete discussions about what cities to target with the atomic bomb did not take place until the spring of 1945. On April 27, 1945, the first “Target Committee” meeting was held in the Pentagon. General Leslie Groves, head of the Manhattan Project, was there at the beginning of the meeting, as was Brig. General Lauris Norstad of the US Army Air Forces. But the meeting was mostly presided over by Groves’ deputy, Brig. General Thomas Farrell. Among the scientists in attendance were John von Neumann and William Penney (but not Oppenheimer).

The basic decisions made at this meeting were regarding operational aspects of the bombing. The use of the atomic bomb would have to be done with visual targeting, not by use of radar. The weather had to be good — no easy thing to predict for Japan in the late summer. The targets should be “large urban areas of not less than 3 miles in diameter existing in the larger populated areas… between the Japanese cities of Tokyo and Nagasaki… [and] should have high strategic value.” A list of possible targets that met this criteria was given: Tokyo Bay, Kawasaki, Yokohama, Nagoya, Osaka, Kobe, Kyoto, Hiroshima, Kure, Yawata, Kokura, Shimosenka, Yamaguchi, Kumamoto, Fukuoka, Nagasaki, Sasebo. Of these, Hiroshima was noted as “the largest untouched target not on the 21st Bomber Command priority list.” Tokyo, on the other hand, was “now practically all bombed and burned out and is practically rubble with only the palace grounds left standing.” It was further noted that they had to take into account that the policy of the 20th Air Force was now “systematically bombing out” cities “with the prime purpose in mind of not leaving one stone lying on the other,” and that they would not likely reserve targets just for the Manhattan Project.1

1945-04-28 - Nordstad - Target Information

This list of targets was forwarded on the next day and someone — probably Groves — indicated that Hiroshima was target #1, Kyoto target #2, Yokohama target #3,  and that other targets of high interest included Tokyo Bay, Fukuoka, Nagasaki, and Sasebo.2 Why Kyoto? A target data sheet, compiled on July 2nd, gives some indication of its perceived strategic value. Kyoto, according to this summary, was a major rail connection between Osaka and Tokyo, had several major factories inside of it (producing “ordnance and aircraft parts” as well as “radio fire control and gun direction equipment”), and numerous “peace time factories [that] have been converted to war purposes.” It also had a new aircraft engine factory that could turn out an estimated 400 engines a month, which would make it the second largest such factory in Japan.3 It had a population of over a million people, of which a “sizeable proportion” of the workers commuted to war production plants. “Many people and industries are being moved here as other cities as destroyed,” another datasheet noted. Its construction was “typical Jap city” — lots of wooden residential houses, and thus very flammable.4

At the Second Meeting of the Target Committee, Kyoto increased in perceived importance. This meeting was held in J. Robert Oppenheimer’s office at Los Alamos on May 10-11, 1945, and was dominated by scientists in attendance. Along with discussing the ideal burst altitude of the bomb, calculated to destroy the largest amount of “light” buildings (e.g. housing), the scientists also discussed targets. At this point, the target list was #1 Kyoto, #2 Hiroshima, #3 Yokohama, #4 Kokura, and #5 Niigata. Aside from the aforementioned justifications (population size, industries), the committee report noted that:

From the psychological point of view there is the advantage that Kyoto is an intellectual center for Japan and the people there are more apt to appreciate the significant of such a weapon as the gadget. … Kyoto has the advantage of the people being more highly intelligent and hence better able to appreciate the significance of the weapon.5

No surprise, perhaps, that the scientists would believe that there was strategic value in making sure that other intellectuals saw the effects of the atomic bomb.

Target map of Kyoto, June 1945, with atomic bomb aiming point indicated. This image is a composite of eight separate microfilm images from two maps (Kyoto North and Kyoto South) that I stitched together in Photoshop.

Target map of Kyoto, June 1945, with atomic bomb aiming point indicated. This image is a composite of eight separate microfilm images from two maps (Kyoto North and Kyoto South) that I stitched together in Photoshop. If you want the full uncropped version (7MB), you can get it here.

The plans to bomb Kyoto were serious enough to warrant the creation of a target map, showing the city with a 1.5 mile circle drawn around a starred aiming point — the roundhouse of the railway yards. Even today this is an easy target to find, visually, using Google Maps — it is the site of the Umekoji Steam Locomotive Museum today. One suspects that if Kyoto had been atomic bombed this site would have the same iconic status as the Genbaku Dome/Hiroshima Peace Memorial today.6

On May 15, 1945, a directive was issued to the US Army Air Forces requesting that Hiroshima, Kyoto, and Niigata be put on a list of “Reserved Areas” not to be bombed, so that they could be preserved as atomic bombing targets. Why Yokohama and Kokura was not put on the list as well at that time is not known to me, but presumably Yokohama was known to be a planned target, as it was ruinously firebombed on May 29th. (As an aside, the mushroom cloud from atomic bombing of Yokohama would probably have been visible from the Imperial Palace in Tokyo, according to NUKEMAP3D.) Kokura was added to the “reserved” list on June 27.7

On May 30th, Groves had a morning meeting with Stimson to discuss the targeting decisions. In Groves’ later recollections, Stimson told Groves that on the matter of the bomb targeting, Stimson was “the kingpin” and that nobody else would overrule him. When Groves told him of the targeted cities, Stimson (again, in Groves’ later recollection), told him bluntly: “I don’t want Kyoto bombed.” Groves recalled Stimson telling him that Kyoto was a cultural center of Japan, the former capital of the country, “and a great many reasons” more why he didn’t want it bombed.8 Stimson had been having numerous meetings about the atomic bomb and the firebombing of Tokyo over these days — and was resistant to the new mass bombing tactics. On June 1, Stimson recorded in his diary a discussion he had with the commander of the US Army Air Forces, about the fact that the US policy was now one of mass destruction:

Then I had in General Arnold and discussed with him the bombing of the B-29’s in Japan. I told him of my promise from Lovett that there would be only precision bombing in Japan and that the press yesterday had indicated a bombing of Tokyo which was very far from that. I wanted to know what the facts were. He told me that the Air Force was up against the difficult situation arising out of the fact that Japan, unlike Germany, had not concentrated her industries and that on the contrary they were scattered out and were small and closely connected in site with the houses of their employees; that thus it was practically impossible to destroy the war output of Japan without doing more damage to civilians connected with the output than in Europe. He told me, however, that they were trying to keep it down as far as possible. I told him there was one city that they must not bomb without my permission and that was Kyoto.

Stimson went to President Truman with his concerns a few days later, on June 6th. His diary records the following exchange:

I told him I was anxious about this feature of the war for two reasons: first, because I did not want to have the United States get the reputation of outdoing Hitler in atrocities; and second, I was a little fearful that before we could get ready the Air Force might have Japan so thoroughly bombed out that the new weapon would not have a fair background to show its strength. He laughed and said he understood. Owing to the shortness of time I did not get through any further matters on my agenda.

What was Truman laughing at? If Truman was a clever man, one might guess that it was the apparent contradiction between not wanting to “outdo Hitler in atrocities” but also wanting to make sure there was enough of Japan left to destroy to make an impression when the atomic bomb was ready. But Truman was not known as a clever man — he probably just thought it was amusing that we were becoming so successful at destroying Japan that we’d need to preserve a little more to destroy later.

Groves had not given up on targeting Kyoto, however. He repeatedly attempted to see if Stimson would budge. Kyoto was a rich target — more important than many of the others on the list. Why did Stimson insist on sparing Kyoto? The answer you find on the Internet is straightforward but a little glib: in the late 1920s, Stimson had been Governor-General to the Philippines, and had visited the city and loved it (and had perhaps been there on his honeymoon). Thus there was a personal connection. This is not present in most of the books on the bomb decision, oddly enough — the fact that Stimson opposed bombing Kyoto is mentioned, but other than noting it was a cultural capital, it is not probed much deeper. The historiography on Stimson’s decision is one about the moral underpinnings of it: Was Stimson trying to assuage guilt? Was he trying to preserve better postwar relations with the Japanese? There are competing interpretations, and not a lot of evidence to work from.9

Truman and Stimson, August 1945. Source: George Skadding, LIFE Magazine.

Truman and Stimson, August 1945. Source: George Skadding, LIFE Magazine.

Which brings us, at last, to what interests me the most here. I am not so interested in why Stimson spared Kyoto, or how scholars have interpreted that. What I am interested in is this: Stimson’s attempt to keep Kyoto off the target list for the atomic bomb went to the very top. The list of targets was not finalized until July 25th, 1945, when Stimson and Truman were both at the Potsdam Conference. There, Stimson told Truman for a final time why Kyoto had to be kept off. From Stimson’s diary entry from July 24th:

“We had a few words more about the S-1 program, and I again gave him my reasons for eliminating one of the proposed targets [Kyoto]. He again reiterated with the utmost emphasis his own concurring belief on that subject, and he was particularly emphatic in agreeing with my suggestion that if elimination was not done, the bitterness which would be caused by such a wanton act might make it impossible during the long post-war period to reconcile the Japanese to us in that area rather than to the Russians. It might thus, I pointed out, be the means of preventing what our policy demanded, namely a sympathetic Japan to the United States in case there should be any aggression by Russia in Manchuria.”

Stimson left the meeting thinking Truman completely understood the matter, and the final target order — with Hiroshima, Kokura, Niigata, and Nagasaki (the latter added only then) — was sent out.

But what did Truman take away from this meeting? We can look at Truman’s own diary entry from July 25th:

This weapon is to be used against Japan between now and August 10th. I have told the Sec. of War, Mr. Stimson, to use it so that military objectives and soldiers and sailors are the target and not women and children. Even if the Japs are savages, ruthless, merciless and fanatic, we as the leader of the world for the common welfare cannot drop that terrible bomb on the old capital or the new.

He and I are in accord. The target will be a purely military one and we will issue a warning statement asking the Japs to surrender and save lives. I’m sure they will not do that, but we will have given them the chance. It is certainly a good thing for the world that Hitler’s crowd or Stalin’s did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful. 

This passage reflects an incredible misconception. Truman appears, here, to believe that Hiroshima was “a purely military” target, and that “soldiers and sailors” would be killed, “not women and children.” But of course every city on that list was inhabited primarily by civilians. And by the calculus of war being waged, every city on that list had a military connection — they produced weapons for the military.

This is not to say that there isn’t a distinction between the targets, just that it is slighter than Truman’s diary entry suggests. Stimson was probably trying to say that the cultural value of Kyoto outweighed its value as a strategic target. Stimson was no doubt aware that Kyoto had war industries inside of it, but thought these were worth overlooking. The lack of a large military base in Kyoto made it more of a “civilian” target in his mind than Hiroshima or Nagasaki. But Truman seems to have come away from this discussion with the understanding that it was a stark contrast between a “civilian” target and a “military” one. As J. Samuel Walker has noted, if Hiroshima had been a more important military target, it likely would have already been bombed much earlier — the fact that it was still intact was in part a reflection of its lack of military presence.10

Statistics on "casualties among school children" at Hiroshima, from Medical Effects of Atomic Bombs, volume VI (July 1951).

Statistics on “casualties among school children” at Hiroshima, from Medical Effects of Atomic Bombs, volume VI (July 1951), page 25.

Am I reading too much into one diary entry? I don’t think so. Consider that after the second bomb was dropped, Truman issued a “stop” order on further atomic bombing, telling Secretary of Commerce (and former VP) Henry Wallace that “the thought of wiping out another 100,000 people was too horrible. He didn’t like the idea of killing, as he said, ‘all those kids.'”11 Because both of those atomic bombs did kill a lot of civilians, and a lot of children in particular. In fact, as a postwar report explained, elementary schools were seen as a great data source on the mortality of the bombs because good records were kept “of the fate of the children.” So you get really gristly statistics about the percentage of schoolchildren killed at various distances from Ground Zero — something that really underscores that these “purely military” targets were a little less than “pure.” Sometimes these passages have been taken to argue that Truman really did wrestle with the moral issues, but I think they show something else: that he did not understand them until after the fact.12

As another bit of evidence along these lines, consider what Truman wrote to Senator Richard Russell on August 9th, before he received a detailed report of the damage at Hiroshima:

I know that Japan is a terribly cruel and uncivilized nation in warfare but I can’t bring myself to believe that, because they are beasts, we should ourselves act in the same manner.

For myself, I certainly regret the necessity of wiping out whole populations because of the ‘pigheadedness’ of the leaders of a nation and, for your information, I am not going to do it until it is absolutely necessary…

My object is to save as many American lives as possible but I also have a humane feeling for the women and children in Japan.

Does this look like a man who understands that he signed off an an order that was being used to obliterate Japanese elementary schools, or someone who really still believes that they are primarily destroying “military” targets exclusively?13

I think Truman came away from the discussions about Kyoto with a very incorrect understanding of what the atomic bomb targets were. I think he really, genuinely did not understand the degree to which civilians would compose the vast bulk of the casualties. How could he misunderstand this point? Because of the framing of the discussion, perhaps — Stimson really wanted him to agree with him that Kyoto was somehow a different category of target. Perhaps this is the greatest legacy of the Kyoto decision: it created what looked like a great moral distinction regarding the bomb, one which Truman thought he had taken a decisive stance on. But in the end it confused Truman as to the possible moral options (he was never presented with the question of whether a “demonstration” should be made, for example, or whether Japan should be given a direct warning first), and he chose one apparently under false pretenses.

I don’t think Stimson attempted to purposely mislead Truman, though. Rather, I think the root of Truman’s misunderstanding was that he was a very incurious man when it came to nuclear matters. He liked the idea of the bomb as a source of political power, but he didn’t really get into the details of how it was made or used, not in the way Roosevelt did, and not in the way Eisenhower would. He rarely questioned his advisors, rarely analyzed the issues with independent judgment, and he never grappled with the big ideas. There are many other examples of this from later in his Presidency as well. Despite having his name forever linked to the atomic bomb, one does not get the impression from even his own retrospective, self-justifying accounts that he really took the issues seriously, or even fully understood them. As a result of his lack of interest, and lack of attention, he never thought to ask how many civilians would die at Hiroshima — it doesn’t appear to him to have even been a consideration until after the damage was done.

Notes
  1. Notes on the Initial Meeting of the Target Committee [held on 27 April 1945]” (2 May 1945), in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 1, Target 6, Folder 5D, “Selection of Targets.” []
  2. Lauris Norstad to Director, Joint Target Group, “Target Information” (28 April 1945), in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 1, Target 6, Folder 5D, “Selection of Targets.” []
  3. Kyoto,” (2 July 1945), in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 1, Target 6, Folder 5D, “Selection of Targets.” []
  4. Files from an envelope labeled “New Dope on Cities,” (14 June 1945, but with some files dated later), in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 3, Target 8, Folder 25, “Documents Removed From Groves’ Locked Box.” []
  5. J.A. Derry and N.F. Ramsey to L.R. Groves, “Summary of Target Committee Meetings on 10 and 11 May 1945,” in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 1, Target 6, Folder 5D, “Selection of Targets.” []
  6. The map is found in an envelope labeled “Pictures,” dated 15 June 1945, in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 3, Target 8, Folder 25, “Documents Removed From Groves’ Locked Box.” There was also a map of Niigata and aerial photos of Kokura and Kyoto in the envelope. []
  7. Reserved Areas” (27 June 1945), in Correspondence (“Top Secret”) of the Manhattan Engineer District, 1942-1946, microfilm publication M1109 (Washington, D.C.: National Archives and Records Administration, 1980), Roll 3, Target 8, Folder 25, “Documents Removed From Groves’ Locked Box.” []
  8. Quoted in Richard Rhodes, The Making of the Atomic Bomb (Simon and Schuster, 1986), on 640-641. []
  9. See Jason M. Kelly, “Why Did Henry Stimson Spare Kyoto from the Bomb?: Confusion in Postwar Historiography,” Journal of American-East Asian Relations 19 (2012), 183-203, and Sean Malloy, “Four Days in May: Henry L. Stimson and the Decision to Use the Atomic Bomb,” The Asia Pacific Journal, Vol. 14-2-09, April 4, 2009. []
  10. J. Samuel Walker, Prompt and Utter Destruction: Truman and the Use of Atomic Bombs Against Japan (University of North Carolina Press, 2004), 61-62. Walker is one of the few authors I’ve seen who have pointed out the discrepancy in Truman’s understanding. I also appreciate that his book title properly refers to the use of “atomic bombs” (plural) as opposed to “the atomic bomb.” []
  11. From Wallace’s diary, quoted in Walker, page 86. []
  12. Bart Bernstein wrote an article in the late 1990s which discusses, among other things, the unreliability of Truman’s after-the-fact narratives about his feelings about this, including one completely false document that claims that Truman decided on Hiroshima and Nagasaki himself! The falseness of this is obvious to anyone who knows even a bit about this history, since Nagasaki was not the primary target for the August 9th run, but the secondary. See Barton J. Bernstein, “Truman and the A-Bomb: Targeting Noncombatants, Using the Bomb, and His Defending the ‘Decision’,” The Journal of Military History 62, no. 3 (July 1998), 547-570. []
  13. Truman’s public statements and press releases, as an aside, need to be carefully scrutinized before being taken as evidence of Truman’s point of view, since he did not write many of them. []
Meditations

A bomb without Einstein?

Friday, June 27th, 2014

If Albert Einstein had never been born, would it have changed when nuclear weapons were first produced? For whatever reason, I’ve seen this question being asked repeatedly on Internet forums, as odd as it is. It’s kind of a silly question. You can’t go in and tweak one variable in the past and then think you could know what the outcome would be. History is a chaotic system; start removing variables, who knows what would happen. Much less a variable named Albert Einstein, one of the most influential physicists of the 20th century, and whose importance extended well past the equations he wrote… and those were pretty important equations, at that!

1946 - Einstein Time magazine - detail

Einstein’s 1946 cover of Time magazine. The mushroom cloud is a beautifully executed combination of the Trinity and Nagasaki mushroom clouds.

On the other hand, this kind of science-fiction counterfactual can have its usefulness as a thought experiment. It isn’t history, but it can be used to illustrate some important aspects about the early history of the atomic bomb that a lot of people don’t know, and to undo a little bit of the “great man” obsession with bomb history. Albert Einstein has been associated with the bomb both through his famous mass-energy equivalence calculation (E=mc²) and because of the famous Einstein-Szilard letter to Roosevelt in 1939. On the face of it, this gives him quite a primary role, and indeed, he usually shows up pretty quickly at the beginning of most histories of the Manhattan Project. But neither E=mc² nor the Einstein-Szilard letter were as central to the Manhattan Project’s success as people realize — either scientifically or historically.

In terms of the science, E=mc² gets a lion’s share of attention, most perfectly expressed by Einstein’s portrait on the cover of Time magazine in 1946 (above) with his equation emblazoned on a mushroom cloud. A lot of people seem to think that E=mc² played a key role in the development of the bomb, that the weapon just falls out of the physics. This is wrong. The equation can help one understand why atomic bombs work, but it doesn’t really tell you how they work, or whether you would expect them to even be possible.

The way I like to put it is this: E=mc² tells you about as much about an atomic bomb as Newton’s laws do about ballistic missiles. At some very “low level” the physics is crucial to making sense of the technology, but the technology does not just “fall out” of the physics in any straightforward way, and neither of those equations tell you whether the technology is possible. E=mc² tells you that on some very deep level, energy and mass are equivalent, and the amount of energy that mass is equivalent is gigantic. But it says nothing about the mechanism of converting mass into energy, either whether one exists in the first place, or whether it can be scaled up to industrial or military scales. It gives no hints as to even where to look for such energy releases. After the fact, once you know about nuclear fission and can measure mass defects and things like that, it helps you explain very concisely where the tremendous amounts of energy come from, but it gives you no starting indications.

Eddington's famous plate of the 1919 solar eclipse, which helped confirm Einstein's theory of General Relativity. Very cool looking, and interesting science. But not relevant to atomic bombs. Source.

Eddington’s famous plate of the 1919 solar eclipse, which helped confirm Einstein’s theory of General Relativity. Very cool looking, and interesting science. But not relevant to atomic bombs. Source.

What about the rest of Einstein’s main theoretical work, both Special and General Relativity Theory? They are pretty irrelevant to bomb-making. The physical processes that take place inside atomic bombs are what physicists call “non-relativistic.” Relativity theory generally only shows its hand when you are talking about great speeds (e.g. large fractions of the speed of light) or great masses (e.g. gravitational fields), and neither of those come into play with fission bombs. You can neglect relativity when doing the math to make a bomb.1

An intelligent follow-up question might be: “well, just because relativity theory didn’t play a role in the bomb process itself doesn’t answer the question of whether it started physics on a path that led to the bomb, does it?” Without getting into a long timeline of the “science that led to the bomb,” here, I think we could reasonably summarize the situation like this: Einstein’s 1905 papers (of which E=mc² was one) did indeed play a role in the subsequent developments that followed, but perhaps not as direct a one as people think. E=mc² didn’t inspire physicists to start looking into processes that converted mass to energy — they were already looking into those through an entirely separate (and earlier) line of development, namely the science of radioactivity and particle physics. The fact that huge amounts of energy were released through nuclear reactions, for example, had already been studied closely by the Curies, by Ernest Rutherford, and by Frederick Soddy prior (but only just) to 1905.

Arguably, the most important work Einstein did in this respect was his work on the photoelectric effect (for which he was awarded the Nobel Prize in Physics for 1921), which helped establish the physical reality of Max Planck’s idea of a quantum of energy, which helped kick off investigations into quantum theory in earnest. This had a big influence on the later direction of physics, even if Einstein himself was never quite comfortable with the quantum mechanics that developed in subsequent decades.

The Hahn-Meitner-Strassman experiment apparatus, at the Deutsches Museum in Munich. My own photo.

The Hahn-Meitner-Strassman experiment apparatus, at the Deutsches Museum in Munich. My own photo.

Did any of the relativity work lead, though, down the path that eventually arrived at the discovery of fission in 1939? I don’t think so. The experiments that Hahn, Meitner, and Strassman were doing in Berlin that lead to the discovery of fission in uranium were themselves careful replications of work that Fermi had done around 1934. Fermi’s work came directly out of an experimentalist, nuclear physics context where physicists were bombarding substances with all manner of subatomic particles to see what happened. It was most directly influenced by the discovery of the neutron as a new sub-atomic particle by Chadwick in 1932. This came out of work on atomic theory and atomic modeling that was being done by Rutherford and his students from the early 1910s-1920s. And this early nuclear physics came, most directly, out of the aforementioned context of radioactivity and experimental physics of the late 19th century.

None of which has a strong, direct connection to or from Einstein’s work in my mind. They have some overlaps of interest (e.g. Bohr was a student of Rutherford’s), but the communities working on these sorts of experimental problems are not quite the same as the more theoretical circle that Einstein himself worked in.2 If we somehow, magically, removed Einstein’s early work from the equation here, does the output change much? There would be some reshuffling, probably, but I sort of think that Rutherford would still be doing his thing anyway, and from that much of the other work that led to the bomb would eventually come out, even if it had a somewhat different flavor or slightly different timeline.

My least favorite way of depicting the fission process, where energy (E) is a magic lightning bolt coming out of the splitting atom. In reality, most of the energy comes in the form of the two fission products (F.P. here) repelling from each other with great violence. Source.

This is my least-favorite way of depicting the fission process, where energy (E) is a magic lightning bolt coming out of the splitting atom. In reality, most of the energy comes in the form of the two fission products (F.P. here) repelling from each other with great violence. Source.

Do you even need to know that E=mc² to make an atomic bomb? Perhaps surprisingly, you don’t! There are other, more physically intuitive ways to calculate (or measure) the energy release from a fission reaction. If you treat the fission process as being simply based on the electrostatic repulsion of two fission products, you get essentially the same energy output in the form of kinetic energy. This is how the physics of fission is often taught in actual physics classes, because it gives you a more concrete indication of how that energy is getting released (whereas E=mc² with the mass-defect makes it seem like a magical lightning bolt carries it away). There are other more subtle physical questions involved in making a bomb, some of which have Einstein’s influence on them in one way or another (e.g. Bose–Einstein statistics). But I think it is not totally crazy to say that even if you somehow imagine a world in which Einstein had never existed, that the physics of an atomic bomb would still work out fine — Einstein’s specific technical work wasn’t central to the problem at all. We also have not brought up the question of whether without Einstein, relativity in some form would have been discovered anyway. The answer is probably “yes,” as there were people working on similar problems in the same areas of physics, and once people started paying a close attention to the physics of radioactivity they were bound to stumble upon the mass-energy relationship anyway. This isn’t to denigrate or underestimate Einstein’s influence on physics, of course. What makes Einstein “Einstein” is that he, a single person, pulled off a great number of theoretical coups all at once. But if he hadn’t done that, there’s no reason to think that other people wouldn’t have come up with his theoretical insights individually, if slightly later.

A postwar re-creation of the genesis of the Einstein-Szilard letter.

A postwar re-creation of the genesis of the Einstein-Szilard letter.

What about Einstein’s most direct role, the famous Einstein-Szilard letter of 1939 that influenced President Roosevelt to set up the first Uranium Committee? This is a tricky historical question that could have (and may at some point) an entirely separate blog post relating to it. Its writing, contents, and influence are more complex than the standard “he wrote a letter, FDR created the Manhattan Project” understanding of it that gets boiled down in some popular accounts. My feeling about it, ultimately, is this: if the Einstein-Szilard letter hadn’t been written, it isn’t clear that anything would be terribly different in the outcome in terms of making the bomb. Something like the Uranium Committee might have been started up anyway (contrary to popular understanding, the letter was not the first time Roosevelt had been told about the possibility of nuclear fission), and even if it hadn’t, it isn’t clear that the Uranium Committee was necessary to end up with a Manhattan Project. The road from a fission program whose primary output was reports and a fission program whose primary output was atomic bombs was not a direct one. By early 1941, the Uranium Committee had failed to convince scientist-administrators that atomic bombs were worth trying to build. They had concluded that while atomic bombs were theoretically feasible, they were not likely to be built anytime soon. Had things stayed there, it seems unlikely the United States would have built a bomb ready to use by July/August 1945.

The “push” came from an external source: the British program. Their MAUD Committee (an equivalent of the Uranium Committee) had concluded that a nuclear weapon would be much easier to build than the United States had concluded, and sent an emissary (Mark Oliphant) to the United States to make sure this conclusion was understood. They caught Vannevar Bush’s ear in late 1941, and he (along with Ernest Lawrence, Arthur Compton, and others) wrested control of the uranium work out of the hands of the Uranium Committee, accelerated the work, and morphed it into the S-1 Committee. The name change is significant — it is one of the more vivid demonstrations of the increased degree of seriousness with which the work was taken, and the secrecy that came with it. By late 1942, the wheels for the full Manhattan Project were set into motion, and the work had become a real bomb-making program.

Einstein wasn’t involved with any of the later work that actually led to the bomb. He almost was, though: in late 1941, Bush considered consulting Einstein for help on the diffusion problem, but opted not to push for it — both because Einstein wasn’t regarded as politically reliable (he had a fat FBI file), and his approach to physics just wasn’t very right for practical problems.3 Bush decided that Einstein would stay out of the loop.

Usual, rare anti-Nazi propaganda postcard from 1934, showing Hitler expelling Einstein from Germany, titled "The Ignominy of the 20th Century." It is one of the most blatant visual renderings of Einstein as a "scientific saint." Source.

Unusual, rare anti-Nazi propaganda postcard from 1934, showing Hitler expelling Einstein from Germany, titled “The Ignominy of the 20th Century.” It is one of the most blatant visual renderings of Einstein as a “scientific saint.” Source.

Let’s sum it up. Did Einstein play a role in the creation of the atomic bomb? Of course — his physics isn’t irrelevant, and his letter to Roosevelt did start one phase of the work. But both of these things are less prominent than the Time-magazine-cover-understanding makes them out to be. They weren’t central to what became the Manhattan Project, and if you could somehow, magically, remove Einstein from the equation, it isn’t at all clear that the atomic bomb wouldn’t have been built around the time it actually was built. I don’t think you can really credit, or blame, Einstein for the atomic bomb, in any direct fashion. Einstein did play a role in things, but that role wasn’t as crucial, central, or direct as a lot of people imagine. If you could magically drop him out of history, I think very little in terms of atomic bombs would have been affected.

So why does the Einstein and the bomb myth persist? Why does everybody learn about the Einstein letter, if it wasn’t really was sparked the Manhattan Project? There are two answers here, I think. One is that Einstein was, even before the war, one of the best-known, best-recognized physicists of the 20th century, and was synonymous with revolutionary science and genius. Having him “predict” the atomic bomb with equations in 1905 — 40 years before one was set off — is the kind of “genius-story” that people love, even if it obscures more than it enlightens. It also has a high irony quotient, since Einstein was forced to flee from Germany when the Nazis took power.

But there’s another, perhaps more problematic aspect. In many early copies of the Smyth Report that were distributed by the government, copies of the Einstein letter were mimeographed and loosely inserted. The magnification of Einstein’s role was purposefully encouraged by the government in the immediate period after using the weapon. (And it was even a convenient myth for Einstein, as it magnified his own importance and thus potential influence.) Hanging the atomic bomb on Einstein’s head was an act of self-justification, of sorts. Einstein was the world’s greatest genius in the eyes of the public, and he was a well-known pacifist, practically a scientific saint. After all, if Einstein thought building a bomb was necessary, who could argue with him?

Notes
  1. As Robert Serber puts it: “Somehow the popular notion took hold long ago that Einstein’s theory of relativity, in particular his famous equation E = mc², plays some essential role in the theory of fission. Albert Einstein had a part in alerting the United States government to the possibility of building an atomic bomb, but his theory of relativity is not required in discussing fission. The theory of fission is what physicists call a non-relativistic theory, meaning that relativistic effects are too small to affect the dynamics of the fission process significantly.” Robert Serber, The Los Alamos Primer: The First Lectures on How to Build an Atomic Bomb (University of California Press, 1992), 7. []
  2. For a good, non-teleological, non-bomb-centric approach to the context of 19th- and 20th-century physics, Helge Kragh’s Quantum Generations: A History of Physics in the Twentieth Century (Princeton University Press, 2002), is excellent. []
  3. Einstein wasn’t entirely a head-in-the-clouds physicist, of course. He worked at the patent office, and as Peter Galison has written about, even his famous thought experiments were often motivated by experience with practical problems of time synchronization. And he did help invent a refrigerator with Leo Szilard. But his work on diffusion physics was too abstract, too focused on first-principle analysis, for use in producing a practical outcome. []