Combat Diaries Special Feature

The Atomic Bomb

from After the Battle Magazine Number 41

Introduction

War in its simplest terms is a contest. In ancient times its outcome was decided pure and simple on the battlefield. Later the victory of one side over the other became more and more dependent on invention and manu­facture: from the longbow to the crossbow, from the matchlock to the flintlock, from black powder to smokeless propellant, from single shot to automatic weapon, and so on. There is nothing like a war to stretch man's ingenuity to its utmost and the Second World War was won for the Allies just as much in laboratories and factories as it was on the field of battle.

The idea that a bomb whose effect was produced by `atomic' energy was theoretically possible came with the publication of Albert Einstein's Annalen der Physik in 1907 in which he showed that mass and energy are merely different aspects of the same thing. His equation proved that if any heavy nucleus breaks into two pieces (called fission), the total mass of the two parts is less than that of the original, the difference being accounted for by the release of energy. In theory any element heavier than iron is potentially able to release energy after undergoing fission although in practice the fission barrier, which causes nuclei to split at different times, is lowest in the heaviest elements.

At the beginning of the war uranium was the heaviest element then known to exist. Isolated as far back as the 1780s, and usually referred to as pitchblende, element number 92 was named uranium by Martin Klaproth, a Berlin apothecary, after the planet Uranus which had been recently discovered. Having the atomic weight of 238.08, the metal was first extracted from ore in 1841 and its radio­active properties were discovered in 1896. Comprising two parts per million of the earth's crust, it is considerably more plentiful than gold, and the world's largest producer of high-grade uranium ore in 1939 was the Union Miniere du Haut-Katanga in the Belgian Congo.

In 1932 James Chadwick, working at the Cavendish Laboratory, Cambridge, had dis­covered the neutron - an electrically un­charged particle which could be used as a ^,missile' to split an atom without being deflected. Two years later Enrico Fermi at the University of Rome used a neutron to bom­bard and split a uranium atom, creating in effect a mini atom bomb, although, at the time, he was unaware of what he had actually achieved - the leading scientists of the period claiming that splitting the uranium atom was impossible.

 It was left to three German scientists, Fritz Strassmann, Lise Meitner and Otto Hahn (seen above left to right in 1956), to officially discover fission during their experiments in 1938.

Leading physicists of the time: Niels Bohr of Denmark, Yakov Frenkel of the Soviet Union and John Wheeler in the United States (above, left to right), had all pub­lished papers before the outbreak of war describing what actually occurred during fission. When Fermi was awarded a Nobel Prize in 1938 for his work, he travelled to Sweden with his wife and family, seizing the opportunity to leave Italy and sail for America. Niels Bohr likewise had travelled to the United States to continue his work (although he later returned to Denmark and was there when his country was overrun) and the German experiment was duplicated at the University of Columbia.

From this Bohr deduced that a sustained atom-splitting `chain reaction' could be created, releasing energy which would multiply upon itself in the fraction of a second. Fermi and others were not slow to see the implications: with war now inevitable, if German scientists put two and two together and applied the principle of the chain reaction to produce a bomb, its potentially destructive force would be unlike anything known before or even conceived. A letter was therefore composed, signed by Einstein and addressed to the American President, Franklin D. Roosevelt, warning him of the danger. The Germans had already taken over Europe's richest uranium mine at Joachimsthal (now Jachymov) in Czecho­slovakia and word reached the outside world that those physicists left in Germany were feverishly at work at the Kaiser Wilhelm Institute in Berlin.

Meanwhile, in the United States, the letter had led to the President setting up an advisory committee authorising support for American universities engaged in uranium research. Some $300,000 (the exchange rate was then around $4 to £1) was allocated by the Govern­ment to sixteen research groups.

Bohr and Wheeler had already suggested specifically the isotope uranium-235, differing in its atomic weight, which was only present to the extent of one part in 140. This was later confirmed by experiments at the University of Minnesota. Once having ob­tained enough ore in the first place, which was difficult enough, the seemingly insurmount­able problem was just how to refine it to the absolute purity demanded of the end product to leave a significant quantity of the minute substance U-235. In 1939 there was only one ounce of ordinary metallic uranium in the whole of the United States and the scientists were now talking of several pounds being needed merely for experiments!

The impossibility of transforming one element into another was then an accepted principle of chemistry but this premise was to be proved wrong at the Berkeley Radiation Laboratory of the University of California. There a machine termed a `cyclotron' had been built to accelerate nuclei to the speed required to penetrate an atom. In May 1940, after bombarding uranium, a new, yet un­stable, element was produced - the first man-made element ever - which the two physicists

concerned, Edwin M. McMillan and Philip H. Abelson, christened nep­tunium. Later that year another element was created (the 94th) by Glenn Seaborg (left to right above) which he later called plutonium. The amount created was infinitesimally small and invisible to the naked eye - just a trace on a measuring device - yet there were strong reasons to suspect that the new material would be fissionable like U-235. It opened up an alternative line of research and one which might lead to fission material being produced in a factory and not gleaned out of the ground.

Meanwhile, in the United Kingdom, the Committee for the Military Application of Uranium Detonation - dubbed the MAUD Committee and comprising the elite of Britain's scientists - was deliberating on its findings as to whether the construction of an atomic bomb was possible. When it reported in the late summer of 1941 that such a bomb was not only possible but that its construction should begin without delay, it galvanised forces in America to act. In the States the work of all the research laboratories was being co-ordinated by the Office of Scientific Research and Development (OSRD) under its director, Dr Vannevar Bush. On December 6, the day before America's entry into the war, the first meeting of a newly-formed atomic sub-committee, called 'S-1', was held in Washington with the brief to establish whether a bomb could be produced in America and at what cost. The committee had to submit their findings to the President within six months.

Early in 1942, Bush was able to report that production of U-235 and plutonium (P-239) was probably possible in spite of the fears of the scientists that it would take many years to refine sufficient quantity of fissionable material to make even one bomb, the physicists even holding differing opinions as to how much would actually be necessary. When the S-1 Committee reported back their conclusion was that an atomic bomb could cost upwards of $100 million (up to £764 million in today's inflated money) and might be produced by July 1944.

The MAUD Committee had already stated that no country at war could risk being without such a weapon and disturbing reports from Continental Europe indicated that the Germans had already begun work and that they most probably had an eighteen month start. Although considerable scientific research had been carried out in the United Kingdom, Britain's resources were already stretched to the utmost. With America now fully committed to the war effort and the unrivalled capacity of its industries far away from Hitler's bombers then blitzing England, the President made his decision. America would produce the bomb, whatever the cost, all research and production would be concen­trated in the United States, and British scientists would continue their work in America on a combined effort. The burning question: what sort of lead might the Germans have, and could the Allies catch up in the race to produce the bomb?

The Manhattan Project

On the advice of Dr Bush of the OSIZD, the President put the entire project in the hands of the US Army. Consequently, in June 1942, the Army formed a special unit with the Army Corps of Engineers under the command of Colonel James C. Marshall and, because his headquarters was centred on New York, the unit was code-named the `Manhattan District'. Liaison officer between the new 'District' and the Corps of Engineers was the Army's Deputy Chief of Construction, and a scientist in his own right, Colonel Leslie R. Groves. On September 23, 1942, having been promoted to Brigadier General, Groves was appointed to head the operation, charged with every aspect concerning the atomic bomb, from initial construction to final delivery, including all the scientific, strategic and governmental aspects, with sweeping powers of requisition and appropriation and virtually a bottomless pit of money, the whole operation being termed the Manhattan Project.

When General Groves (seen with is 2 i/c Colonel Kenneth D. Nichols) took over responsib­ility for production of the bomb, the viability of which depended entirely on the manu­facture of sufficient fissionable material, five different production methods were under con­sideration. Three concerned the separation of uranium-235 from the base element uranium­238. The first envisaged the use of electro­magnetic forces, while the second involved a centrifugal method. The third possibility was to use gaseous diffusion through a series of permeable membranes or filters to gradually separate out the U-235. The final two methods dealt with the possible ways of mass producing plutonium using either graphite or heavy­water `reactors'. There was no experience to suggest which of the five possibilities would be the most successful in the long run, but the more important question was, which would be the quickest? With the over-riding knowledge that this was now 1942 and that the Germans had begun their work in 1939, the stakes against backing the wrong horse were too great a risk to take.

Consequently, instead of passing through the usual experimentation, testing, analytical and reporting phases to determine the best course of development of any new product, the S-1 Committee made what was possibly the boldest decision of the entire war: to proceed with all five methods simultaneously. The expenditure would be colossal as a whole new industry was being created, not just once but five times over. It was overkill in the extreme, but it lowered the risk threshold appreciably and, it was hoped, would reduce the technological lead of Germany.

Enrico Fermi was given the task of assemb­ling the first `atomic pile', as the nuclear reactor was then called, to try to create a con­trolled chain reaction using uranium to prove if this could be self-sustaining. Construction of the test reactor called Chicago Pile 1 (CP-1) began on November 7, 1942 in a rackets court at Stagg Field, part of the University of Chicago campus. (A purpose-built building was under construction in the Argonne National Forest, twenty miles outside the city, but this had not been completed on time.)

Here blocks of pure graphite, some 40,000 in all - the production of which was a feat in itself - were gradually stacked in a pile about 24 feet square, supported by wooden scaffold­ing. Each block was machined exactly to size – 4.75 in X 4.75 in X 16.5 in - and half were drilled with 0.75 in holes. The purpose of the graphite was to slow down the number of neutrons escaping from 61b slugs of uranium inserted in the stack. It was calculated that fifty tons of uranium metal would be required before the reaction would begin - a vast amount, way beyond what had been produced to date by the Westinghouse Corporation and the Metal Hydrides Company. Fermi therefore decided that the balance could be made up from uranium oxide, putting the more efficient pure metal in the centre of the pile, with the oxide on the outside. The holes in the graphite were for the insertion of cadmium coated control rods. These would absorb the neutrons while they stayed within the core but provided a method of gradually activating the reaction as they were slowly withdrawn.

Throughout November scientists toiled under conditions of great secrecy to construct the primitive reactor. By December 1 the forty-eighth layer of blocks had been put in position and the instruments and Fermi's calculations indicated that the critical stage was about to be reached. As each metal slug was put into position, neutron activity in­creased. By eleven o'clock that evening with the fifty-first layer in place, all was set for the great experiment

About twenty people were assembled on the balcony overlooking the court the following morning. No one really knew exactly what would happen if a critical chain reaction was created. Three control rods were available which it was hoped would keep the kettle from boiling over, so to speak. One could be auto­matically inserted by controls on the balcony; a second would be anchored by a rope which could be cut in an emergency, so dropping it back into the pile. The third was the one which was to be slowly withdrawn to start the reaction. In case the rods failed, a three-man `fireman' squad was standing by with buckets of cadmium solution ready to throw it over the graphite to absorb the neutrons.

At 10.00 a.m. on Wednesday, December 2, Enrico Fermi gave the order to remove the emergency rod which was secured by its rope and a scientist stood by with an axe ready to drop it back if necessary. At 10.37 a.m. Fermi ordered the last rod to be withdrawn to thirteen feet. Recording instruments measured the flow of neutrons, and the trace became steady after its initial surge. Every ten or fifteen minutes the rod would be pulled out another few inches, and each time the trace levelled off. Not until 3.20 p.m. in the after­noon was the stage reached when the readings, instead of remaining steady, con­tinued to climb of their own accord. For twenty-eight minutes the same situation was maintained with the recorders indicating a steady upward line - a nuclear chain reaction had been produced for the first time.

The experiment not only proved that a slow chain reaction could be created by concentrat­ing a specific quantity of uranium metal, it also indicated that U-235 (or P-239) would be required to create the instantaneous reaction necessary to produce an atomic bomb. The guesstimates of the amounts of these isotopes that would be required for one bomb varied by a factor of ten, i.e. the true amount could end up to be ten times more or less than the estimate! With only 0.7% of U-235 present in U-238, and only 6% of that present in uranium ore, thousands of tons of rock would be necessary. Thus the supply of sufficient ore was critical yet it was in extremely short supply.

Fortunately Edgar Sengier, director of the Belgian mine in Katanga, acting with fore­sight and acumen after hearing about uranium's potential military value in 1939, had quietly shipped 1,200 tons of high-grade ore from the Congo in August 1940 packed in 2,000 steel drums. While officials of the Manhattan Project were scouring all known sources of supply, this cache was lying in a warehouse on Staten Island, New York! In September 1942 word of its existence reached the US Government and it was snapped up for $1.60 per lb. Additionally, arrangements were made to ship further stockpiled supplies direct to America from Africa.

With the supply of ore assured, General Groves could turn his mind to the formidable problems in extracting the U-235. To date only microscopic amounts had been produced in laboratories and the technology did not even exist for mass production. Therefore, as soon as he took charge of the Manhattan Project, General Groves set out on a fact ­finding tour of the various research pro­grammes to assess the potential of the three different processes being considered.

The first was the centrifuge method being worked on by the Westinghouse Research Laboratory at Pittsburg, Pennsylvania. There the basic idea was that the lighter uranium­ 235 isotope could be separated from the heavier U-238 in a metal drum spinning at enormous speed. So far there had been no positive results and the General was not impressed with the `academic' pace of those involved. Success seemed very dubious and he recommended that the process be dropped in favou of all-out efforts on the other two methods which would benefit from the resources thus saved.

The General's next visit was to see the gaseous-diffusion operation at New York's Columbia University. The principle involved, although barely beyond the drawing-board stage, was to convert U-238 to a gas and pass it through a filter in which the holes were so small that they would only let molecules through. The lighter U-235 would theoretic­ally pass through quicker so that the gas on the other side would be very slightly more con­centrated in U-235. If this operation was repeated again and again, this content would gradually be increased until pure fissionable material was obtained. However, the problems in so doing were in the realms of fantasy as one was building up a product molecule by molecule. First, thousands of filters would be required and none had ever been constructed with holes so small. Con­sistency would have to be 100 per cent - each of the billions of holes had to be just one ten­thousandth of a millimetre - otherwise precious molecules would be lost.

Second, the amount of filter material required could be measured not in square inches but in acres! It hardly needs repeating that uranium is a heavy metal, not a gas, and, even if and when so converted, it would be so corrosive as to destroy any other metal, pipe or pump with which it came into contact, let alone a fragile filter. Groves and his team were hardly fired with enthusiasm for this method which seemed years away from fruition.

Next on the list was the electromagnetic process under study at Berkeley University in California. There, Professor Ernest O. Lawrence was in charge and under his direction a `calutron' had been constructed combining a huge magnet and a crude vacuum chamber shaped like the letter `C' inserted between the poles, the idea being to divert the lighter U-235 molecules electro­magnetically. When the General asked how much U-235 had been produced so far, the answer was 225 microgrammes of a substance which was still only 30% pure! To scale up production to end up with pounds of pure material would require tens of thousands of magnets with thousands of scientists working round the clock in huge plants using enor­mous amounts of uranium - nothing more un-feasible had ever been proposed before.

Nevertheless, a manufacturing location for an, as yet, unproved process to produce the, as yet, unseen material by a production plant not yet designed had already been chosen by Colonel Marshall on a virgin site at Oak Ridge, some eighteen miles west of Knoxville, Tennessee. There an abundant water supply with the promise of plenty of electrical power from the Tennessee Valley Authority dams in an area of almost no habitation, yet having good communications by road and rail, seemed ideal, and General Groves gave his immediate approval. The task of constructing the huge complex was given to the engineers of the Stone and Webster Company with AAA priority - the highest possible - with orders to begin construction before the end of 1942 regardless of the fact that no-one knew the size, shape or specification of the plant required! The Manhattan Project was almost

Oak Ridge

X-10 at Oak Ridge was located in a valley several miles away from the uranium plants.  This picture was taken of the reactor shortly before its shutdown on November 4, 1963 – the twentieth anniversary of its start up.  Now it is preserved as a National Historic Landmark.

'The topography is such that a number of operations could find reasonably flat areas divided by protective hills', reported the three­-man investigative team in the spring of 1942. 'The driving distance to Knoxville is less than 20 miles, and service from two important rail­roads is immediately available. Water from the Clinch River is regulated . . . and because of the nearby Norris Dam is relatively free of silt. A relatively small part of the land is under cultivation, indicating that a small number of families would have to be moved.'

Once approval was given in September, the Manhattan District acquired the 92-square­mile site at a cost of $2,600,000. Some 1,000 families were forced to abandon their homes and the whole area was sealed off by guards, roadblocks and fences. Within a month civil engineering plant had moved in and bull­dozers and steam shovels began to prepare the site. By November work had started on the first buildings which later served as head­quarters for the Manhattan Engineer District and the nerve centre for the entire US nuclear war programme. Almost simultaneously work began on the huge housing and community facilities which would be needed for the vast population of engineers and scientists who eventually totalled 82,000. Accommodation in the new 'city' was so difficult that some people had to commute from up to 75 miles away.

On February 1, 1943 ground was broken on the first actual building known as Y-12 which would house the electromagnetic process, and which was to be operated by Tennessee Eastman, a sub­sidiary of the Kodak company. Before the process had been completely developed, top Stone and Webster engineer, August C. Klein, was entrusted with the job of directing all work on the site. The Berkeley magnets had been scaled up to 250 feet long with a magnetic field so strong that ferrous tools would be pulled from the hands of workmen in the vicinity. Consequently all moveable equipment had to be made of non-ferrous metals. The magnets, weighing from 3,000 to 10,000 tons, were constructed by Allis­ Chalmers and because copper could not be spared in the quantities required for the coils, silver from Fort Knox was substituted - 6,000 tons of it!

Altogether there were five 'Alpha' buildings which contained two oval-shaped 'racetracks', each track having 96 separating units - the calutrons - which could all be operated independently. The four smaller `Beta' plants had two rectangular racetracks with 36 calutrons. Some of the calutrons had two ion guns, others four.

After some disastrous teething troubles, one. of which involved sending all the magnets back to the manufacturers to correct the faults, the Y-12 plant came on stream on January 27, 1944 and began a round-the-clock operation in three shifts. It was found that during each 'run' only about 10 per cent of the uranium put in at one end came out at the other - the other 90 per cent was lost on the walls and linings of the apparatus. Therefore every few days each calutron had to be dismantled and completely cleaned, chemically and by other methods, to try to recover the deposits. The few grams of black powder that were the end product of the Alpha plant arrived at two collecting stations labelled U-238 and U-235. The latter was still only 13 to 15 per cent pure so that after washing it chemically, the powder was fed back through the Beta machines to improve the enrichment. In the process, 90 per cent would again be lost and the whole process started again. Some of the U-235 atoms were lost when they actually became fused into the walls of the stainless steel collecting points by the sheer power of the magnetic beam, and this was only solved by copper-plating the steel and then dissolving the copper and extracting the uranium.

Oak Ridge was also the location of the plant to operate the second method of U-235 extrac­tion - by gaseous diffusion. The Carbide and Carbon Chemicals Company were given oper­ational charge of the project and work on the K-25 complex, as it was termed, began on September 10, 1943. Designed by a specially­ formed subsidiary of the M. W. Kellog Cor­poration, the Kellax Corporation ('Kell' for Kellog and `X' for secret), the huge U-shaped K-25 diffusion process building measured 2,450 feet long, 400 feet wide and 60 feet in height. It had a total area of 44 acres and required 350,000 cubic yards of concrete, 40,000 tons of structural steel, 15,000 tons of steel sheet and 5 million bricks.

British experts rated its success at one in a thousand as the problems were incredible. Uranium hexafluoride gas had to pass through three thousand stages in the `cascade' to slowly filter out the U-235 atoms. The nickel membranes, with their holes just two millionths of an inch in diameter, were so difficult to construct that the process used is still classified. The pumps had to work at the speed of sound yet could not be lubricated in any way as the gas would cause an explosion if it came into contact with oil. Some 250,000 man-hours went into their design and develop­ment alone - equivalent to one engineer working for 100 years. Tolerances were so fine and the complexities so great that many believed the plant impossible to build and that even if built it would not work. Nevertheless, K-25 began operating on February 20, 1945 but the resulting U-235 only had a purity of 1.1 per cent. By then the pressure to get enough fission material for a bomb led to the decision to feed the product of the K-25 plant back through the Y-12 plant for final enrich­ment.

Another method of U-235 production was also constructed at Oak Ridge in 1944 using a different principle entirely - thermal dif­fusion. This had been developed completely independently by the US Navy in their quest for an alternative form of submarine propulsion but it was adopted as a further string to the nuclear bow even though the end product was only about 1.4 per cent pure. The Ferguson Company built the plant S-50 in a record sixty-nine days and production began on September 16, 1944. Once again the impure U-235 was fed into Y-12 for final enrichment.

The fourth phase of the nuclear story at Oak Ridge was the construction of a nuclear reactor X-10, under the jurisdiction of the University of Chicago, which was to serve as a pilot plant for the large plutonium-producing reactors to be built at Hanford, in the state of Washington, on the other side of America. In this reactor it was intended to produce suf­ficient plutonium to provide scientists with enough material to develop a method for the chemical separation of this man-made element. Work on the X-10 plant began just two months after Dr Fermi had successfully created the first chain reaction. It was com­pleted by November 1943.

The Hanford Plant

B Reactor, the world’s first plutonium reactor, was constructed on the Hanford site near Richland in Washington State.  After producing the fission material for the wartime bombs, it was shut down shortly after the end of the war.  It was reactivated in 1948 and operated almost continually until its retirement in February 1968.  In 1976 it was named a national landmark by the American Society of Mechanical Engineers and is maintained for the US Department of Energy as a shutdown facility by UNC Nuclear Industries.  Altogether there have been nine government production reactors at  Hanford.  Eight have been deactivated, the ninth – N Reactors – completed in 1963 is expected to continue to operate into the 1990s.

What Oak Ridge was to uranium, so Hanford in the southern central part of Washington State on the Pacific coast of the United States became to plutonium. Like Oak Ridge, Hanford was sparsely populated, had abundant water available from the Columbia River and electricity supplies from the Bonne­ville and Grand Coulee dam systems.

As atomic bomb material, plutonium was a more attractive investment as the critical mass of P-239 is around ll lbs (5kg) - less than a third of that required for U-235. The project was put in the hands of the Du Pont de Nemours Company but Fermi's team were obviously closely involved with the design of the reactor. Construction began on June 7, 1943 and the usual superlatives abound: 25 million cubic yards of earth excavated and 780,000 cubic yards of concrete brought in; 40,000 tons of structural steel, 158 miles of railway track laid down and 386 miles of roads constructed. Over 45,000 construction workers were employed in the building phase. The atomic pile itself, called Reactor B, con­tained 2,000 tons of graphite and was pene­trated by 2,000 process tubes. The pile, as tall as a four-storey building, was surrounded by ten inches of cast iron and four feet of con­crete.

Plutonium is produced when the uranium in the pile is subjected to the slow chain reaction. In the process some of the uranium is converted into P-239 although it remains in the uranium ingots, slugs or rods. The problem in this case was how to separate the two and, after several experiments, it was found that bismuth phosphate was a good carrier of plutonium. Thus, in addition to the reactors, separation plants had to be built and huge installations, labelled B and T Plants, were constructed in the desert some five miles south of B Reactor. For safety reasons, both were situated three miles apart and designed to be operated under remote control. Once the separation process was begun behind the eight-foot-thick walls, no human being would be able to enter the processing areas. Irradiated ingots were transported in heavily shielded casks along specially constructed railway lines between the pile and the separation buildings.

On September 13, 1944, Enrico Fermi was on hand to load the first uranium slug into the graphite pile, the first of thousands inserted over the next few days. Two weeks later the critical point was reached and the control rods withdrawn to begin the chain reaction. Power began to build up nicely, sustaining the reaction, until suddenly, three hours later, the gauges began to fall. Slowly at first, but inexorably lower and lower until finally the pile shut itself down completely. The failure was baffling and many different possibilities were put forward as to the cause. Then on the evening of September 27, almost like a sleep­ing monster, the pile suddenly came to life again. Power was raised to 9,000 kilowatts - the same level reached the day previously –before once again the chain reaction died away. The problem was eventually diagnosed as the production of a gas (called xenon-135) as a by-product of the fission process which was absorbing neutrons and `poisoning' the reactor. The cure was to load an additional 504 uranium-bearing tubes (a 25 per cent increase) to boost capacity and overcome the neutrons lost.

By December 25, 1944, B Reactor had turned out its first irradiated slugs and, after separation in T Plant, the first plutonium was ready for shipment by the end of January 1945.

Los Alamos

The original Administration building T-1 at Los Alamos

At this stage in the story we must go back to October 1942 when it was becoming increas­ingly evident that the Manhattan Project would need a specific research site to design and manufacture the bomb itself. Because of its crucial importance it was given a separate title - Project Y - and a search began in sparsely-populated New Mexico for a safe and secure location for this most secret of all installations. After examining several possibil­ities, General Groves settled on one that encompassed the existing buildings of the Ranch School at Los Alamos, a 7,300-foot pine-forested plateau in the Jemez Mountains, twenty miles north-west of Santa Fe. The General appointed Dr J. Robert Oppenheimer to be project director against the advice of security chiefs who considered that his political background made him an unaccept­able risk.

On November 25 the go-ahead was given to take over nearly 50,000 acres including the 50 school buildings at a total cost of $414,971 - a low figure in view of the fact that over three­quarters of the area was already held by the US Forest Service. Administration of Los Alamos was to be under the jurisdiction of the University of California.

Huts and buildings of every description soon spawned across the site, but until suf­ficient housing had been constructed, the scientists (or `engineers' as they were termed for security reasons) were billeted in ranches and private homes throughout the surround­ing area. Oppenheimer personally recruited most of the scientists he required and he arrived at Los Alamos in March 1943. Security was extremely tight - all the top men had cover names (Oppenheimer was Mr Bradley), driving licences had numbers in­stead of names and were not signed, and all mail in and out was censored (the postal address was simply PO Box 1663, Santa Fe). The whole site was ringed with barbed wire patrolled by military police and a pass system regulated who was able to go where.

The problem central to the Los Alamos scientists was the method of assembly of the atomic bomb. Where in a reactor the criticality could be controlled by moving neutron-absorbing rods, a nuclear bomb would have to be sub-critical in the aircraft delivering it, but somehow be made instantly critical at the point of impact on the target. Additionally, the scientists were dealing with two completely different explosive elements, U-235 and P-239. Work initially centred around the idea of using an artillery gun barrel to fire one piece of fission material at the other: separated they were insufficient to go critical but as soon as they hit each other the chain reaction would begin, 'fast' neutrons would be released and the explosion would follow - all in a split second. The method was simple and radar timing devices could be used to fire the gun at an appropriate point above the target to avoid the possibility of the bomb hitting the ground before detonation. How­ever, there was one snag. When the P-239 is manufactured in a reactor from U-238, some of the plutonium absorbs a neutron and is transformed into P-240. This material under­goes spontaneous fission and this would cause a plutonium bomb to begin the chain reaction before reaching supercriticality. The result would be a premature explosion producing

little energy just like a damp squib. This prob­lem did not occur with uranium, only plutonium, and by July 1944 it was evident that a plutonium bomb could not be assembled fast enough by the gun method to overcome this effect. It was all the more frustrating as it appeared likely that plutonium would be the first material avail­able and in greater quantity than uranium produced by the painfully slow processes at Oak Ridge. Therefore, while the gun was adopted for the uranium bomb, and a suitable barrel ordered from the Naval Gun Factory in Washington, DC, an alternative design was sought for the plutonium.

It was one of Project Y's physicists, Seth Neddermeyer, that proposed a revolutionary idea of assembling a supercritical mass from every direction at once. His answer to the seemingly impossible was to surround a sphere of P-239 by shaped explosive charges which would blow inwards many other pieces of P-239 to smash into the centre core at a speed of millionths of a second which would overcome the problem of premature criticality. The idea was enthusiastically taken up by another scientist who believed that the resulting compression of the P-239 might even mean that less plutonium would be required to create an atomic explosion. Neddermeyer called his method `implosion'.

No one knew if the fantastic tolerances of instantly detonating the explosive from every point of the compass at once could be achieved. On the other hand it was still doubt­ful if Oak Ridge could produce enough uranium for the gun bomb. The news from Germany was equally disturbing, for reports of the increased production of `heavy water' (an alternative to graphite in a reactor) in­dicated that production of plutonium might not be far away.

Although spontaneous fission was likely with the implosion method, a safeguard to ensure that there was no doubt was to design an `initiator' which could be placed in the very centre of the plutonium core and produce enough neutrons at the right moment to start the chain reaction of its own accord. This object, the size of a nut, was developed by Dr Charles Critchfield using separate pieces of beryllium and polonium. These two metals, when combined, give off neutrons and his idea was that when the implosion shock wave hit the initiator (inserted in the plutonium by casting the core in two hemispheres), the two metals would combine producing the spark to light the fire.

Trinity

Fat Man Mk1 is slowly eased off the back of a truck. This was identical in

size to the Hiroshima bomb minus the ballistic trimmings.

It was pretty certain that the uranium gun bomb, based on proven ballistic principles, would work first time and as it would take months to produce enough U-235 for just one device, there seemed no point in wasting this on a test explosion. The plutonium bomb with its untried implosion technique of assembly was another matter and a test firing was con­sidered essential to prove whether it would work.

The Los Alamos area itself could not be used and a short list of eight possible locations, from Texas to California, was drawn up early in 1944. By the summer all had been surveyed and the choice narrowed to an 18 by 24 mile section of the US Air Force bombing range in southern New Mexico - the Jornada del Muerto (Journey of Death) - cupped between two mountain ranges. It was also conveniently just 160 miles south of Los Alamos. The code name they gave it was Trinity.

The principal occupier at the proposed site was the McDonald ranch which was retained as a final assembly point for the bomb which was to be detonated a mile away at a point termed Ground Zero. By October

plans for the construction of the base camp, ten miles further away to the south, were drawn up and two months later the construction was com­pleted and the permanent MP guard detach­ment increased. Shelters were built 10,000 yards north, south and west of Ground Zero. The bomb itself was to be mounted on a high tower to lessen the chance of sucking up too much earth which would subsequently descend as radioactive debris. Escape routes were planned and an enormous 214-ton steel container, 25 feet long, 12 feet in diameter with walls more than 14 inches thick, dubbed Jumbo, was fabricated with great difficulty in Ohio and transported to the site. The initial idea was to explode the bomb inside it, so that in the event of a misfire or a partial explosion of the TNT only, it was hoped that the plutonium would be trapped in the bottle where it could be recovered for another at­tempt. When a regular supply of plutonium from Hanford was assured, the precaution was deemed unnecessary and Jumbo was not used.

As a dress rehearsal in order to calibrate the scientific instruments and gain some advance knowledge of the sort of explosion which could be expected, a hundred tons of TNT were set off before dawn on May 7, 1945. As a result additional roads were constructed around the site to facilitate quicker communications.

Several press releases were prepared to explain away the nuclear blast to the media should it be successful, one of which said that a remote ammunition dump had accidentally exploded. Should it become necessary to evacuate any area, the news would include the fact that gas shells had gone off. A more sinister communique was ready to report the strange deaths of many famous scientists in an accidental explosion in New Mexico.

By now sufficient plutonium had reached Los Alamos to fabricate sections for the two hemispheres of P-239 which were transported to the Trinity site on July 12 on the back seat of an ordinary army staff car. When the core reached Alamogordo it was taken to one of the rooms in the McDonald ranch house which had been prepared for its reception. The following day a convoy arrived with the main explosive assembly of the bomb, driving straight to the tower where it was unloaded into a canvas tent erected at the base. There it was partially dismantled ready for the core to be inserted.

Meanwhile back at the ranch the nuclear assembly team were preparing to bring together for the first time an amount of plutonium never before concentrated in one piece. In case anything should go wrong, jeeps were stationed outside, engines running, for immediate getaway. Slowly the pieces forming the two halves of the sphere were brought together, then the initiator was slipped into place before the two hemispheres were joined together. Once assembled, the core was driven to the test tower where the bomb was waiting. There it was inserted into place and the remainder of the explosive `lenses' built up around it. By 10.00 p.m. all was finished.

At 8.00 a.m. on July 14 the bomb began its journey to the top of the tower. Mattresses were piled twelve feet high to break its fall if anything should go wrong with the electric hoist or the cable should break. Gently it was eased up through the trap door in the floor of the firing chamber 100 feet above the sur­rounding desert. Once in position the detonators were inserted in the bomb casing leaving only a final connection to arm the device.

The test was scheduled for early morning on Monday, July 16 and during Sunday all the leading scientists and observers began to assemble at Trinity. General Groves arrived at base camp during the afternoon just as it began to rain. The weather forecast was bad with the chance of thunderstorms. The steel test tower, the tallest structure for miles, was a veritable lightning conductor; not only might freak lightning set the bomb off prematurely, but moisture could cause short-circuits on the intricate wiring to the detonators. Then wind and rain could precipitate fall-out over a wide area.

However, were the test to be delayed, this could result in even wider implications. Six thousand miles away in Berlin, President Truman and Prime Minister Winston Churchill were attending the Potsdam Con­ference with Russian premier Josef Stalin. At that very moment they were waiting for word from Alamogordo as to the success or other­wise of the test, hoping this would come before they met with Stalin again. With Germany out of the war the intended target for the bomb had switched to Japan, against which Stalin was poised to declare war. The Allies were hoping they had an ace card, but it was a card which might easily turn out to be a joker.

Shortly after midnight General Groves, accompanied by Robert Oppenheimer, left base camp for the main VIP control centre at the southern bunker, six miles from the bomb. By 2.00 a.m. the weather began to improve and two hours later the wind had dropped and the rain had stopped. With the promise of stable conditions for the next two hours, General Groves made the decision to go at 5.30 a.m. Mountain War Time.

The final stages of the arming procedure began. Searchlights were switched on to guide the two B-29 observation aircraft, and thirty minutes before zero hour the five-man team guarding the tower retreated. General Groves returned to base camp which was the nearest point where observers could remain out in the open. Even then everyone was instructed to lay face down and cover their eyes with their hands.

At 5.10 a.m. the countdown began and at D minus 45 seconds a switch was thrown to activate an automatic firing timer. At 29 minutes and 45 seconds past the hour the bomb exploded.

The blast was felt throughout the southern portion of New Mexico and into Arizona in the west and Texas in the east. Windows were blown out up to 200 miles to the north-west and 150 miles away people reported the sun coming up and going down again. Many of the measuring devices and instruments which had been set up in the surrounding desert were swept away and most of the film in the cameras was completely fogged by radiation.

As monitor teams began to follow and track the radioactive cloud as it drifted slowly north­eastward at ten miles per hour, a special lead­lined Sherman tank with Enrico Fermi and Herbert Anderson inside clanked over the desert to Ground Zero across an expanse from which all vegetation had disappeared. A saucer-like depression 1,200 feet in diameter and 25 feet deep surrounded Ground Zero but of the test tower there was no sign. It had been com­pletely vapourised and its foundations were subsequently discovered seven feet beneath the crater floor. The whole area was coated with a jade-green opaque glass where the desert sand had been melted and fused into what was later called Trinitite. Jumbo, 800 feet beyond the detonation point, had survived intact but its surrounding steel girder tower had been snapped clean. As the Sherman approached Ground Zero, the geiger counter aboard went berserk.

The monitoring teams following the fall-out cloud were also detecting heavy amounts of radiation in a band thirty miles wide and a hundred miles in depth and some radioactivity was detected 120 miles from the test site.

In Berlin the news was reported to the President enigmatically:

“Operated on this morning. Diagnosis not yet complete but results seem satisfactory and already exceed expectations. Local press release necessary as interest extends great distance.”

Wendover

At the same time that scientific and manu­facturing effort was being expended in untold amounts to produce a bomb, the USAAF had activated a special unit to carry it into action - the 509th Composite Group commanded by Colonel Paul W. Tibbets, a superb pilot with a distinguished record with the 97th Bomb Group in Europe and North Africa. Colonel Tibbets had been given the job of choosing a suitable Stateside training base and he decided on Wendover Army Air Field west of the Great Salt Lake on the Utah ­Nevada border. The area could guarantee more than 300 sunny days per year which was an important prerequisite for developing the bombing techniques required as it had already been laid down that the bomb would be dropped only in a daylight operation under visual aiming conditions.

The Group was assembled on December 17, 1944 equipped with the B-29 Superfortress and began to practise dropping single 10,000 lb bombs from 20,000 to 30,000 feet. The dummy bombs were fatter than normal, simulating the `Fat Man' plutonium bomb - so called because of its similarity with Winston Churchill's physique! (The slimline uranium bomb was named `Little Boy' after President Roosevelt.) Immediately the bomb was released the aircraft had to make steep 158-degree turns, diving to gain speed to outrun the shock-wave. At the outset, only Colonel Tibbets knew the precise nature of the new weapon, the crews merely being informed that it was a special sort of new bomb.

By the end of May 1945, the Group had been equipped with nine new, specially modified B-29s and on June 5 the first crew left Wendover for their forward base at Tinian.

Tinian

Tinian lies three miles off the southern coast of Saipan in the Mariana group of islands in the north-west Pacific. After a tre­mendous pre-invasion bombardment, Task Force 52 had landed General Schmidt's V Amphibious Corps, comprising the 2nd and 4th Marine Divisions, on Tinian on July 24, 1944. The battle was noted for the first use of napalm in the Pacific; ironically just over a year later it was to be host to yet another new weapon. The island was finally secured on August 1 with over 6,000 Japanese dead, and the Americans immediately set about convert­ing it into an advanced base for the eventual invasion of Japan. Seabees bulldozed four 8,500-foot parallel runways on the northern tip of the island, aptly named North Field air­strip, while another aerodrome sited on the western side became West Field. Roads were laid down and, because Tinian resembles Manhattan in shape, they were given names such as Eighth Avenue and Park, Grand Avenue, Fifth, 42nd and 110th Streets, and Broadway.

On July 14, 1945, just as the Trinity test was nearing its climax, the components for Little Boy - the uranium bomb - left Los Alamos. First deliveries of U-235 from Oak Ridge had begun in March 1945, and the gun parts were readied by the spring, yet it was not until July that enough fissionable material had been produced to make one core. On July 16 the bomb and half the uranium, the latter sealed in a lead-lined container, were loaded aboard the cruiser Indianapolis for the journey to Tinian where it arrived ten days later. The remainder of the uranium was flown in direct by C-54 transport a few days later.

Waiting for it on the island was a detach­ment of Los Alamos scientists who were to assemble the bomb and the 509th who were to drop it. Colonel Tibbets and the crew of his aircraft Enola Gay had been earmarked to carry out the first mission. Captain William S. Parsons of the US Naval Ordnance Division, who had led the development of the uranium gun, would be aboard the B-29 to load the U-235 projectile once in the air.

Meanwhile Hanford had supplied Los Alamos with sufficient material to fabricate a second plutonium bomb with a promise of more in the pipeline to make a third Fat Man. The P-239, consigned under the code-name 'Bronx', was already en route to Tinian by air. Whereas the uranium from the K-25 plant had taken months to produce, plutonium was now coming on stream and, with the proven success of the implosion method of ignition, a sustained campaign of atomic bombing with P-239 seemed more viable.

On August 4, seven crews of the 509th were finally briefed on the true nature of their mission. They were shown a film of the Trinity explosion and, although the word 'atomic' was not mentioned, the reason for the tight turns after dropping the practice bombs was now only too clear. Because of the large amount of radioactive debris sucked up on the static test firing in the desert, the Manhattan Project scientists had decided to try to avoid this in future by detonating the air-dropped bomb several thousand feet above the ground. However the blast effect would thereby be increased and the danger to the aircraft might well be more severe and crews were especially warned not to fly near the smoke rising from the explosion.

The following day, General Groves' deputy on Tinian, Brigadier General Thomas F. Farrell, reported that the weather conditions over Japan were finally suitable for a visual mission and Enola Gay was prepared for a take-off early the next morning. At North Field Loading Pit No. 1, the black and orange-painted Little Boy was winched into the belly of the B-29 while the two escorting observation aircraft were made ready for the 13-hour return flight. The target for the first bomb had been specified as Hiroshima, located in the south-west of the principal Japanese island of Honshu. It was the seventh largest city in Japan with a wartime peak population of 380,000 but five completed evacuations had reduced this figure to an estimated 245,000. It was a modern admin­istrative, communications and military centre built primarily on the fan-shaped alluvial deposits of the Ota River which flows through the city.

According to the United States Strategic Bombing Survey conducted after the raid, published under the `Secret' classification in 1947, the reasons for selecting Hiroshima as the target for the first bomb were as follows:

a. The city of Hiroshima had received only an insignificant amount of prior damage; therefore, what damage resulted could be attributed to the atomic bomb.

b. Being built on a deltaic formation, it was nearly flat for a distance of 6,000 feet in all directions from the aiming point, and for more than 15,000 feet in the southerly quadrant.

c. At various intervals within a 6,000-foot radius from the aiming point there were enough substantially constructed, multistory, commercial buildings of representative structural types to allow comparative study of the effects.

d. Because of the prevalence of wood con­struction throughout the city, and the pattern of the water courses which formed natural firebreaks, the incendiary effects of the bomb could be analyzed.

e. Within the area were representative types of short-span, fixed bridges in sufficient num­hers to permit a relative study of the effective­ness of the weapon against them.

f. Hiroshima was well equipped with public utilities (water, gas, electricity, sewers) and inter-urban transportation so that conclusions could be drawn regarding the relative vulner­ability of these facilities.

g. The principal feature which detracted from the target value was the remoteness of the industrial concentration from the center of the city.

The secondary target was Kokura, a hundred miles to the south-west on the southernmost Japanese island of Kyushu, with the third choice, Nagasaki, another hundred miles south-west.

At 2.45 a.m. on Monday, August 6 Enola Gay lifted off the runway in the company of the instrument aircraft, The Great Artiste, piloted by Major Chuck Sweeney, and a third B-29 commanded by George Marquardt, equipped with photographic equipment. A quarter of an hour later, once course for Japan, 1,700 miles away, had been set, Captain Parsons began the final loading of the uranium gun which was completed within fifteen minutes.

At five minutes past six, having reached Iwo Jima, the formation altered course for Hiroshima. The Japanese coastline was sighted at 8.30 a.m. (Tinian time) whereupon Captain Parsons made a final check on the radar fuses which were set to explode the bomb at 2,000 feet. Eleven minutes later the reconnaissance aircraft, sent ahead to check each target, reported weather fine with few high clouds and a visibility of 10­15 miles over the primary target. Wind was from the south about 5 mph.

The appearance of the weather 'plane had caused the Hiroshima Chugoko Regional Military Headquarters to sound the air raid sirens at 7.09 a.m. (Japanese time was one hour behind). As the aircraft left the area the all-clear was given at 7.31 a.m. when most Japanese who worked in the city were on their way to their offices or factories. At 8.06 a.m. the Matsunaga lookout station reported two aircraft proceeding north-west, corrected to three aircraft three minutes later. The sound of aircraft engines was picked up by the Nakano searchlight battery at 8.14 a.m. yet no further air raid warning was sounded.

Captain Parsons logged the Enola Gay as levelling out at 32,000 feet at 8.38 a.m. (7.38 a.m. on the ground). At 9.09 a.m. the target was in sight and at 9.15 a.m. Tinian time the bomb aimer, Major Tom Ferebee, an­nounced: `Bombs away!'

'It was hard to believe what we saw,' wrote Captain Parsons later. `We dropped the bomb at exactly 9.15 a.m. Japanese time (sic) and got out of the target area as quickly as possible to avoid the full effect of the explosion. A tremendous cloud of smoke arose which completely blotted out Hiroshima. When we felt the explosion it was like flak bursting close by. We stayed over the target area for two minutes.

`The whole thing was tremendous and awe-­inspiring. After the missile had been released I sighed and stood back for the shock. When it came, the men aboard with me gasped "My God!" and what had been Hiroshima was a mountain of smoke like a giant mushroom. A

thousand feet above the ground was a great mass of dust, boiling, swirling, and extending over most of the city. We watched it for several minutes, and when the tip of the mushroom broke off there was evidence of fires.'

Hiroshima

Post-war research has indicated that the bomb exploded at 580 metres (1,903 feet) ±15 metres directly above a point (also referred to as Ground Zero) in the grounds of the Shima Hospital. The power of the bomb has been assessed at 12,500 tons of TNT of which 35 per cent was released as thermal radiation, 17 per cent as radioactive radiation, and the remainder as blast energy. Within a millionth of a second the nuclear chain reaction built up a temperature in the core of several million degrees Centigrade. In 0.1 millisecond a fireball of 300,000°C was created which expanded to 250 metres in diameter one second after detonation.

Survivors stated that the explosion seemed like a vast combustion of magnesium filling the entire sky. Its reported colour was greenish-white and yellowish-red, lasting for two to four seconds. At the same time an over­powering heat wave emanated from the source of the flash. The entire city was darkened by a dense pall of smoke and dust which limited visibility to a few feet. From a distance, a grey-­coloured, mushroom-shaped cloud was seen expanding and covering the whole area, reaching a height of 23,000 feet within four minutes. This column began to disintegrate within eight minutes, the top becoming detached

In the centre of Hiroshima, a violent blast of air immediately followed the flash, knock­ing down trees and poles, tearing sheets of galvanised metal from buildings and squash­ing or knocking over houses. The temperature of the ground beneath the burst reached an estimated 3,000 to 4,000°C and the heat rays caused flash burns up to 13,000 feet away.

Hundreds of fires were reported to have started within ten minutes, spreading in all directions aided by the large proportion of highly-combustible materials which are used in the majority of Japanese housing. A fire storm began to develop, a wind of 30 to 40 mph blowing continuously in towards the burning area for two or three hours after the explosion. This was followed by rain contam­inated with radioactive fall-out. All wooden buildings within half a mile of Ground Zero collapsed and were burned down. Most concrete buildings escaped complete destruction but were badly damaged and gutted by fire. Broken windows were found up to ten miles away.

Several bodies have carried out research since the end of the war to try to determine the total number of casualties. Because of the large-scale destruction of local society and the disorganisation which followed, probably the most accurate is that compiled by the Hiro­shima City Survey Section (see table) which recorded the number of casualties up until August 10, 1946. Ironically its report was subsequently lost for twenty years.

Nagasaki

Prior to the dropping of the first bomb, a declaration of the terms under which the sur­render of Japan would be accepted had been transmitted to the Japanese Government on July 27 following the conference of the Big Three powers at Potsdam. The final sentence read: `The alternative for Japan is prompt and utter destruction', a rather oblique and vague reference to the impending use of the atomic bomb, about whose existence the Japanese were left in ignorance. The lack of a positive response led to the Allied decision to embark on a series of knock-out blows to force a submission.

With the forecast of approaching unsettled weather over Japan, the second plutonium bomb was quickly being made ready on Tinian. This time Major Chuck Sweeney's crew were detailed to carry the bomb and they had already carried out a dummy run, dropping a Fat Man without the nuclear core into the sea to test the fusing and detonators. As The Great Artiste, their aircraft on the Hiroshima run, was one of the instrument 'planes, they switched machines and borrowed Bockscar. Commander Fred Ashworth was in charge of fusing the weapon, with Captain Kermit Beahan as bombardier. The target would be the number two on the first raid, Kokura, with the alternative choice of Nagasaki in case Kokura was obscured by cloud.

Shortly before take-off the first problem to befall the flight became apparent when the engineer reported the fuel valve which con­trolled the reserve tank was inoperative. At this late stage the implications of an aborted mission were too great and as Iwo Jima had a suitable runway, there was the possibility of landing there on the return flight should fuel run low.

At 1.56 a.m. Japanese time on August 9 Bockscar took off followed later by the photographic and instrument-carrying B-29s. Slowly climbing out over the Pacific, Major Sweeney set course for Iwo, passing the island at 5.04 a.m. Making landfall at the Yako­shima rendezvous, the second problem arose with the non-arrival of the photographic aircraft. Major Sweeney circled, waiting for the missing B-29 which was carrying the British scientist Dr William Penny and Group Captain Leonard Cheshire as observers.

With the fuel shortage exacerbating the situation, after forty minutes Major Sweeney gave up and headed in to Kokura. Although the weather aircraft had earlier advised that both targets were clear, by the time they reached the city it was mid morning and industrial haze obscured the arsenal which was the aiming point. Frustrated, Major Sweeney tried a second run over the target. Still in­visible, the B-29 was now attracting anti­aircraft fire and Japanese fighters were heard scrambling on the radio. To linger over the target was to invite trouble, yet Major Sweeney swung Bockscar round for yet another pass. Nevertheless his orders were specific: the bomb was only to be dropped visually. With the warning of fighters ap­proaching from below, there was no other choice but to set course for the alternate target of Nagasaki. With fuel running short they would have to take the direct route which led right over the Japanese fighter airfields on Kyushu, make one pass over the city and then try to make Okinawa, the mainland island wrested from Japan at the end of June.

As Bockscar approached Nagasaki, the two-­tenths cloud cover reported by the reconnaiss­ance aircraft now appeared to be nearer nine-­tenths. Responsibility for choosing between jettisoning the bomb and three years tremendous effort into the sea, or going against orders and dropping it by radar rested with Commander Ashworth. Time was running out and a decision had to be made if the aircraft was not to ditch or even crash-land in Japan.

'Go ahead and drop it by radar, if you can't do it visually,' he told Sweeney, only too aware of the fact that he was countermanding ex­plicit orders. Fortunately for him, twenty-five seconds before release, a hole appeared in the clouds and the bombardier took over visually. At 11.02 a.m. - just over nine hours after leaving Tinian - the bomb was released.

The plutonium bomb exploded at 1,650 feet (±32 feet) above the Urakami district of Nagasaki, post-war researchers having pin­pointed the position of Ground Zero to within 20 feet. Although its explosive power has been estimated at 22,000 tons of TNT, the magnitude of its effect was deflected by the hills which divide the city and the Nakashima river district escaped with lesser damage.

In After Years

Within hours of the news of the second bomb reaching Tokyo, the Japanese heirarchy were meeting with the Emperor to thrash out once again the pros and cons of accepting the terms of the Potsdam Declaration. The argu­ments for and against continued but, with the entry of the Soviet Union into the Far Eastern war the previous day with decisive effect, on August 15 the Emperor broadcast his ac­ceptance.

As soon as it was considered safe to do so, numerous teams entered the cities of Hiro­shima and Nagasaki to begin investigations into the effects wrought by the bombs. While assessments were prepared by the individual town civilian administrations, the United States Strategic Bombing Survey, established by the Secretary of War on November 3, 1944 to prepare detailed technical reports on the effects of Allied bombing on German, French and Belgian targets, had its brief widened on August 15, 1945 to encompass Japanese targets. President Truman requested that the Survey conduct a study into all types of air attack in the war against Japan, not just the atomic ones. A complement of 350 officers, 500 enlisted men (the military personnel com­prising 60 per cent from the Army and 40 per cent Navy) and 300 civilians were detailed for the task, operating from a headquarters established in Tokyo early in September 1945, with sub-headquarters in Nagoya, Osaka, Hiroshima and Nagasaki. Mobile teams operated in other parts of Japan, the islands of the Pacific and the Asiatic mainland.

The survey interrogated more than 700 Japanese, military, government and industrial officials and recovered and translated many documents to build up a picture of the Japanese economy and war production, factory by factory, industry by industry. As far as Hiroshima and Nagasaki were concerned, the teams began their studies in October and were joined for the month of November by a 16-man mission from Britain. The short report of the latter was published by His Majesty's Stationery Office in 1946. The US Survey, on the other hand, ran to several volumes. Report No. 3 from the Office of the Chairman, Nos. 5 and 9 on Air Raid Protection from the Civil Defense Division, and No. 13 from the Medical Division were all published by the US Government Printing Office, while the more interesting Physical Damage Division reports (Nos. 92 and 93) and the Urban Areas Division reports (Nos. 59 and 60) were classified as secret.

Volume 1 of Report No. 92, completed in May 1947, explained that no attempt had been made to pass judgment on the overall effectiveness of the atomic bomb, the purpose of the Survey being only to tell as complete a story as possible of the physical damage suffered by the stricken cities as a result of both the direct and indirect effects of the explosions. Reports of damage to buildings of all existing types - industrial, commercial, and residential - were included, together with some conclusions concerning the relative degrees of resistance inherent in the several types to the direct and indirect results of the atomic bomb forces. Likewise, there was con­siderable discussion regarding building contents' vulnerability and degree of damage in relation to the types of construction. Fire also was reported on at length since it resulted from both direct and indirect causes and was

responsible for a large proportion of the physical damage. Other subjects studied and reported on were: damage to machine tools, bridges, chimney stacks, services, and utilities.

Since then countless books, articles and papers have been written and published cover­ing every aspect of the bombings. Memories of what total war really meant in 1945 have faded and the passage of time has seen the armchair critics of another age bring into question the ^‘morality' of the construction and use of the atomic bomb. It is not the Editor's intention to enter into the argument. Our role is merely to state the facts and let every reader decide for himself or herself what he or she would have done had they been in President Truman's shoes.

Firstly, the President inherited a fact of life: the decision to develop the bomb had already been taken by Britain and America early in the war in the light of the knowledge that German scientists were already at work on nuclear research.

When a national army is fighting on its own territory to defend its own capital city, the resistance is bound to be bitter. Churchill stated that the Battle of London, were it to be fought street by street, could devour an entire enemy army. After the invasion of Europe, the Western Allies refrained from a drive to capture Berlin, which General Omar N. Bradley, commander of the US 12th Army Group, warned Eisenhower could result in 100,000 casualties, and the Russians later stated that they had suffered that many men killed during its capture.

Although Germany was knocked out long before the atomic bomb was even tested, the war in the East was expected at the time to last well into 1946. In the island-hopping cam­paign across the Pacific the Japanese had already fought tenaciously to hold territory which was not theirs, and during the invasion of Okinawa, which was Japanese territory, they had sacrificed 120,000 military and 42,000 civilians in its defence. The advent of the kamikazi represented a scaling up of these 'do or die' tactics which the Americans could expect to encounter in ever-increasing numbers in the invasion of Kyushu, scheduled for November 1, 1945, and Honshu, planned for March 1, 1946.

The success of the Trinity test on July 16, with the guarantee of further regular supplies from Hanford, offered the possibility of launching a series of hammer blows which might force an early surrender and avoid the necessity for the long and costly campaign which would have inevitably resulted, like Germany, in the total destruction of Japan by conventional bombing.

For nearly twenty years after the end of the Pacific war, Harry Truman refrained from public comment while his critics became more noisy in their condemnation of his decision to use the weapon. His answer came in February 1965 during a television interview:

'It was a question of saving hundreds of thousands of American lives. I don't mind telling you that you don't feel normal when you have to plan hundreds of thousands of complete, final deaths of American boys who are alive and joking and having fun while you are doing your planning. You break your heart and your head trying to figure out a way to save one life. The name given to our invasion plan was OLYMPIC, but I saw nothing godly about the killing of all the people that would be necessary to make that invasion. The casualty estimates called for 750,000 Americans - 250,000 killed; 500,000 maimed for life. I could not worry about what history would say about my personal morality,' concluded the former President. 'I made the only decision I ever knew how to make. I did what I thought was right.'

The Enola Gay

Next to the Wright Brothers' Flyer and Lindbergh's Spirit of St Louis, the Enola Gay has probably had the greatest impact on civilization of any aircraft ever to have flown. The first two planes hang majestically in the central bay of the Air and Space Museum on the Mall in Washington while the B-29 which dropped the first atomic bomb sits dis­assembled in a warehouse in Silver Hill, Maryland.

The plane's pilot, Paul Tibbets, believes that the controversy surrounding the plane's mission over Hiroshima has prevented the Enola Gay from assuming a position of honour in the new Smithsonian Museum. For his part, General Tibbets believes the bombs should have been dropped. “It never occurred to me in 1944 and 1945 that you would even think if you had a weapon of that type that you wouldn't use it. We were out to win a war, not to prolong it or stall it or fight with one hand”. Tibbets, now the president of an air charter service, has expressed disappointment that 'the government and quasi parts of it are ashamed of the Enola Gay and what she did during the war. I think they would all like to play ostrich, i.e. "put their heads in the sand" and hope the problem [use of the A-bomb] would disappear.'

In a 1965 article, Life magazine noted that some Smithsonian officials did 'worry that the plane would be out of place alongside objects intended to engender pride.' However, in discussing plans for the new Air and Space Museum that was then on the drawing boards, other officials pointed out that because the plane 'figured so prominently in history it is a legitimate subject for display.'

While the plane still remains controversial for those people who see it as a symbol of the evils of nuclear war, its size rather than any efforts to keep it hidden remains the basic reason why the Smithsonian has not restored the Enola Gay to exhibition condition. The Life article pointed out that the plane's 141­foot wing span and 99-foot length made it too large for any then-existing museum. Even the new Air and Space Museum does not contain an exhibit area large enough to hold the assembled plane.

Walter Boyne, the museum's curator, conceded that it would be possible to place only the fuselage in one of the bays. However, he points out that even this section of the plane would displace several other aircraft

and would probably engender criticism for not having restored the entire plane. As an alternative to keeping the Enola Gay in storage, Boyne says he has hopes that the plane can be sent to some other air museum where it can be reassembled and exhibited indoors. To further this goal, the curator indicates that tentative negotiations have taken place with a museum 'in a most approp­riate location' and if an agreement is reached, he says the Smithsonian would help with the restoration.

If the Enola Gay has not yet found a per­manent home, it began its life designated to be a special plane for a unique mission. When the B-29 rolled off the Boeing assembly line in Omaha in April 1945, it had already been picked as the plane to drop the first atomic bomb in combat. While directing the training for the mission at Wendover, Utah, the then ­Colonel Tibbets ordered the B-29 to be modified as it was being built.

Wanting the fastest possible aircraft, he had the Enola Gay stripped of all heavy turrets and the central fire control system in order to make the plane 7,700lbs lighter. He also had the B-29 specially equipped with electric, reversible pitch propellers which had originally been designed for use on Consolid­ated Aircraft's B-32 bomber, the unsuccessful challenger to Boeing's Superfortress. Explain­ing his requisition of the props, Tibbets said, `We couldn't afford to pile up at the end of a runway with that load [the atomic bomb]. These [the propellers] gave us a chance to backwater if anything went wrong once we started rolling.'

After flight testing and preliminary train­ing, the Enola Gay flew to the Marianas on June 29, 1945. On Tinian, it began flying warm-up missions against Japan and on August 6, with Colonel Tibbets at the con­trols, the plane dropped the first atomic bomb on Hiroshima at 9.1S a.m., ushering in the nuclear age.

Despite the long-running debate over whether the United States should have dropped the bomb, Tibbets himself has never seen the plane's mission as anything which should have caused controversy. He saw it as a military assignment and said ‘I did what I was told to do'. Thomas Ferebee, the bombardier on the Hiroshima flight, verbalised the same thoughts: ‘I've always felt compassion for those at Hiroshima that day, but I never got a guilt complex over it. It was just like any other mission military people are asked to do.'

In any case, following the bombing mission, the Enola Gay stayed in the south Pacific until November, when Robert Lewis, the plane's regular pilot, flew it from Tinian to the Air Force Base at Roswell, New Mexico. Even though it had established its claim to fame, the B-29's flying career was not over. At Roswell, Tibbets flew the plane in routine training exercises. He later recalled, `The Enola's really a very boring airplane. Nothing ever happens to her, not even vibrations.' Describing a series of three high altitude missions in one day, Tibbets remembered, ‘All the sceptics said we'd lose an engine. Enola didn't even cough.'

Because the plane was one of the very few B-29s that had been modified to carry an atomic bomb, Tibbets flew the Enola Gay back to the Pacific in July 1946 to take part in the Bikini bomb tests (see After the Battle No. 28). The plane did not drop any of the bombs, however, and it returned to the United States after the operation.

On orders of General Carl Spaatz, the Air Force's Commanding General, the Enola Gay was then placed in mothballs at Davis ­Monthan Air Force Base in Arizona to preserve it until a decision was made about its ultimate disposition. In June 1949 it was taken out of its protective cocoon and, on July 3, Tibbets with his former bombardier, Major Ferebee, aboard, flew the plane to Chicago where he formally turned it over to the Smithsonian Institution. After being exhibited at the National Air Fair then being held concurrently with the third Air Force Association Convention, the Smithsonian placed the plane inside the former Douglas aircraft plant at Orchard Place, now the site of O'Hare Airport.

Plans called for the Enola Gay to remain indoors until the Smithsonian could build its Air Museum in Washington. With the out­break of the Korean War, however, Douglas reactivated its assembly line and on short notice, Smithsonian officials had to move the B-29 and other planes being stored in the plant outdoors and to the mercy of the harsh Chicago-area weather. Finally, on August 31, 1951, the Enola Gay was flown from Orchard Place to Andrews Air Force Base to await a permanent home.

At least throughout the 1950s, the plane and her mission remained a source of pride to the nation. In 1952, MGM released Above and Beyond which told the story of Colonel Tibbets, his training of the 509th Bomb Group for its nuclear missions, and the actual dropping of the bomb on Hiroshima. While Tibbets said he had already had more than enough publicity, he felt that he was ‘public property' and the American people were entitled to know what had happened to their property during the war. With the assistance of the Air Force, MGM was able to tell a story that Tibbets felt was ‘so close to realism that really we would have to be very, very nit­picking to separate what was on the screen from reality'.

Hollywood followed Above and Beyond with a series of movies made in co-operation with the Air Force which portrayed the activities of the Strategic Air Command during the Cold War. Strategic Air Command (1955), Bombers B-52 (1957), and Gathering of Eagles (1963) pictured the bomb as a necessary deterrent to Soviet aggression, with the clear implication that Hiroshima and Nagasaki had been necessary military actions.

Meanwhile, the Enola Gay herself sat out­doors at Andrews Air Force Base unattended, collecting birds' nests, suffering weathering to her unprotected body and even being van­dalized by servicemen stationed on the base. In contrast, Bockscar, the B-29 which dropped the bomb on Nagasaki, remained on display at the Davis-Monthan Air Force

Museum in Arizona from September 1946 to September 1961. It then made the last known Air Force B-29 flight when it flew to Wright­Patterson Air Force Base in Dayton, Ohio, where it has been on permanent indoor display ever since.

The Confederate Air Force in Texas has a B-29 which it flies - see After the Battle No. 8. Now Brigadier General (Retired), Tibbets flew the plane in 1976 in a simulation of his Hiroshima mission and promptly stirred up a rash of protests both in the United States and Japan.

In the summer of 1960 the Smithsonian began dismantling the Enola Gay and moved the pieces to its `preservation headquarters' at Silver Hill, Maryland. When a storage facility was completed. In the summer of 1961, the plane was moved out of the elements for the first time and it remains dismantled in Building 21. Initially, officials indicated the plane would not be exhibited until it could be placed in the new air museum. Responding to an inquiry about the Enola Gay in 1967, the museum's director, S. Paul Johnston, ex­plained that there were `no immediate plans to re-assemble the airplane, largely because we do not have any display space large enough to house it.'

In fact, during the 1960s, plans to build a national air museum on the Mall in Washington remained stalled. The original concept for a museum as part of the Smithsonian complex dated from August 1946. At that time, the few planes on exhibit such as the Spirit of St Louis were in the Smithsonian's original red brick building. The Wright Brothers' plane had not yet been returned to the United States from England where the brothers had sent it in reaction to the Smithsonian's label saying Samuel Langley's plane was the first aircraft capable of flight.

With the rapid growth of aviation after World War II, however, the need for a museum dedicated solely to flight became obvious and Congress finally authorised the Mall site in 1958. Nevertheless, it did not appropriate $2 million for architectural design and layout until 1965, and did not change the name of the museum to the National Air and Space Museum until 1966. The Vietnam War provided a further delay in construction because of the reordering of budgetary priorities during the conflict. As a result, the museum did not finally open until July 4, 1976.

By that time, however, the nation's attitude toward nuclear warfare had undergone a decided change. At least part of the dis­enchantment with the use of atomic weapons came from Hollywood's changing portrayal of the military in general and of the atomic bomb in particular. Following the example of Stanley Kramer's bleak vision of the after­math of nuclear holocaust in On the Beach (1959), film makers produced such anti-bomb movies as Dr Strangelove and Fail Safe in 1964 and The Bedford Incident in 1965, all picturing the dangers of accidental nuclear warfare. In addition, such books as John Hershey's Hiroshima and Robert Lifton's Death in Life had described in graphic detail the results of the Enola Gay's mission on the Japanese people. Consequently, the plane had become a symbol of the horrors of nuclear warfare.

When asked shortly after the Air and Space Museum opened why the Enola Gay was not on exhibit, a museum official explained that the plane was simply too large to fit inside the building. At the same time, he conceded that even if the Museum had sufficient room, the plane might not have been displayed because of potential criticism by anti-bomb people.

Walter Boyne, the museum's curator, recognised the significance of the Enola Gay both as a milestone in aeronautical design and in altering political thinking on the nature of warfare. Consequently, he said that if there was a 'legitimate requirement to have an exhibit concerning nuclear warfare, then certainly the B-29 would come in and there would be no apologies for it. Nobody can say that the Enola Gay is intrinsically bad. It is simply an instrument of history.'

Despite Boyne's personal desire to have the B-29 exhibited, however, he remained sensi­tive to the emotions the plane engenders from those who see it as a symbol of the evils of nuclear war. As a result, the Smithsonian staff would prefer that the plane receive no undue publicity. Boyne explained that if the plane got unwarranted attention, it might cause protests which could reach into Congress. According to Boyne, such protests were 'not profitable to anybody. We don't satisfy the people who protest because basically we can't alter history. We don't satisfy ourselves because we know that we're spending energy •answering their questions that could be better 'pent doing something else.'

The Enola Gay itself remains out of sight for most tourists at the Silver Hill facility although the museum does permit an oc­casional Japanese visitor to photograph the plane and legitimate researchers examine it. ~n addition, some restoration work has been lone on' he plane. In 1970, Vince LoPrinzi, a Museum's library. When he first saw the B-29, he recalled, 'It looked pretty forlorn with its wings off and sitting in a wooden cradle. It just didn't seem right to me that such an historic airplane should be allowed to deteriorate so I asked if I could try to restore it.'

Restoring an historic aircraft to the Smithsonian standards involves much more than repainting and fixing broken windows. While not committed to putting a plane in flyable condition, Smithsonian curators use authentic parts wherever possible. In replac­ing the broken plexiglass in the Enola Gay's nose, for example, LoPrinzi found the bolts were stripped and had to be replaced. Since he couldn't 'just go to the hardware store and buy new bolts' LoPrinzi said he had 'to scrounge around. I found some parts that were taken from scrapped B-29s; others from old air­plane graveyards; and still others in the Smithsonian's shop.'

Despite its years outdoors in the elements, LoPrinzi found the Enola Gay in pretty good condition. Before being transferred to another home base, the pilot worked first in the cock­pit area and then began moving back through the engineer, navigator, and bombardier panels.

According to Lo Prinzi, the bomb bay sections, one of which was modified to handle the 'Fat Man' bomb, were in excellent con­dition. The tail gunner's compartment, how­ever, required work. While the pilot said he would like to see the Enola Gay put on display, such a decision had no bearing on his restoration work: 'It's a matter of personal satisfaction and I would do it even if the air­plane never gets outside the warehouse!'

When Lo Prinzi was transferred, all restor­ation work on the B-29 came to a halt. Given the Smithsonian's priorities for restoration of other planes also in storage at Silver Hill and the museum's budgetary limitations, it is unlikely that more work will be done in the near future unless another air museum can be found in which the reassembled B-29 can be exhibited. If such negotiations are unsuccess­ful, however, Walter Boyne has indicated that facilities will be improved at Silver Hill so that people can view the Enola Gay at close range in Building 21.

The plane they see may not be one of the most significant aircraft in the development of aviation. But next to the Wright Brothers' Kitty Hawk Flyer and Lindbergh's The Spirit of St Louis, the Enola Gay has undoubtedly affected the course of civilization and of inter­national politics more than any other aircraft.