Churchill's Bomb

by Graham Farmelo

  On 29 November, Bohr sailed for America, under a smokescreen helpfully created by the government, which told the press that he was to be involved in ‘post-war planning of international scientific cooperation’. At the dockside in New York a week later, British security officials handed Bohr and his son over to a posse of FBI agents, who issued them with official papers and pseudonyms, Nicholas and Jim Baker, before driving them off in a cab to a nearby hotel. The agents thought they had done an immaculate job of preserving the secrecy of the visit, until one of them noticed on the side of an item of luggage, stencilled in large black letters: NIELS BOHR.22 The two Danes were allocated a relay of armed detectives, who shadowed them during their travels across America, and even slept outside their bedroom door.23

  In Washington DC, Bohr visited Groves in his office on the fifth floor of the new War Department Building. In all meetings like this, the General behaved like the quintessential nononsense CEO, underscoring his determination to deliver his agreed mission: ‘to produce a practical military weapon in the form of a bomb in which energy is released by a fast neutron chain reaction in one or more of the materials known to show nuclear fission’.24 A delivery date for the weapon had not yet been agreed, but the General will have stressed the project’s great urgency, the absolute priority of secrecy and that he – and only he – was in charge of it. He had no truck with the traditions of openness practised by those ‘crackpot’ scientists at Site Y and did not even seem to accept that he reported to a civilian Commander-in-Chief. He told Chadwick a few months later that ‘the President had no powers and no authority to give away military secrets’.25

  It speaks well of Groves that he was not put off by Bohr’s philosophical mumblings, but took them in his stride. The General trusted his scientists’ overwhelming recommendation – no doubt forcefully articulated by Oppenheimer – that Bohr would be a huge asset to the Manhattan Project and would be welcome on the staff at Site Y. Apparently not wanting to be shackled, Bohr declined Groves’s offer and continued with his freewheeling consultancy with Tube Alloys.26 The Americans were under the impression that he would ideally like to be based at the Institute for Advanced Study in Princeton, a sanctuary of academic enquiry where he could work with Einstein and other scholars, contribute to the Bomb project and be within convenient travelling distance of Washington.27 Thrilled at the prospect of recruiting another illustrious member, the Institute’s director Frank Aydelotte arranged for the Rockefeller Foundation to fund a temporary post for their visitor, and had a generous offer on the table for him when he arrived in Princeton four days before Christmas. Disappointingly for Aydelotte, the deal turned sour a day later.

  Bohr was looking forward to meeting his old friend Einstein. Separated by Hitler for over a decade, they settled down for a talk over a cup of tea in the common room of the Institute, overlooking the lawn stretching out towards the distant woods. Minutes before, Aydelotte had offered to employ Bohr, perhaps hoping that he and Einstein might collaborate for the first time. But it was not to be. In the crowded common room, Einstein greeted Bohr and quickly began to bombard him with criticisms of the Manhattan Project, as if it were no more secret than the front pages of the day’s newspapers. Einstein regurgitated the views of his friend Szilárd – the ‘American army was making a frightful mess of the uranium work’ and it was a thoroughly good thing that Bohr had come to the United States as he would surely ‘be able to put this right’.28 According to the account of this encounter given by Akers a few weeks later, this was a ‘devastating experience’ for the well-intentioned Dane, who knew that if he became associated with such indiscreet talk about the Bomb, the authorities would not allow him anywhere near the Manhattan Project. Bohr now knew that joining the Institute was ‘quite impossible’.

  Two days after Christmas, Bohr and his son began their journey to the Manhattan Project’s headquarters at the mysterious Site Y.29 They took the train to Chicago, where they met Groves and his science adviser Richard Tolman, who accompanied them on the sleeper. En route, the General preached for hours to the Great Dane about the crucial importance of not disclosing even a morsel of classified information and of saying nothing about the supposed German Bomb programme. The journey was a trial for the poor General, who knew he had to treat his guest with the softest of kid gloves. As the vast, empty landscapes of the Midwest spooled past, Bohr distractedly looked out of the train window, mumbling as if he had a mouthful of marbles, while Groves leaned over to get close enough to his guest to understand what on earth he was saying.

  Late at night on New Year’s Eve, their train pulled into a quiet little town in the New Mexico desert. After stepping out of their railway carriage into the biting cold, they were picked up in an army car and driven to a nondescript office in Santa Fe run by Dorothy McKibbin, ‘the atomic lady’, as insiders dubbed her. After they had been issued with security passes, the party was taken off on the final stage of its journey, a thirty-five-mile drive, the car making its way along a single-access road zigzagging up a desert mountainside they could scarcely see, the air thinning and cooling by the minute. Niels Bohr was about to see for himself a project he had dismissed on his previous visit to Princeton four years before as ‘impracticable’.30

  At Site Y, Oppenheimer and his colleagues greeted Bohr like a monarch returning from exile. Here was a scientific hero who had been determined to stay in his own country for the entire war until the Nazis’ actions forced him to leave. Now, he was back with his colleagues to work with them, listen to their doubts about the project and buoy their spirits. Within five minutes, he was talking with Oppenheimer, spilling the beans about the Anglo-American project he had heard about in London and Washington.

  By the end of the next day, Bohr had seen that this was a laboratory unlike any other in the history of science, surrounded by plunging canyons, in a wilderness planted only with sagebrush and piñon pines, and strewn with jutting formations of sandstone. It was like the setting of a John Ford Western, the kind of place that brings home the immensity of the entire North American continent. The site, which had ‘opened’ nine months before, still had a makeshift feel, a combination of a temporary army base, a jerry-built workplace for experimenters and theoreticians, and a mountain resort.31 About 3,500 people were working on ‘The Hill’, behind two barbed-wire fences, where Groves was assembling the most intense concentration of top-class physicists the world had ever seen. Normally it was easier to herd kangaroos than to persuade such people to follow executive orders en masse. But here Oppenheimer had them all lined up and ready to work for as long as it took to solve the problem of building what they euphemistically referred to as ‘the gadget’.

  The technical facilities on The Hill were beyond munificent. Scientists expected virtually any item they ordered to be delivered within days from universities, industrial firms and the military, which jumped at the arrival of every order from the site. One group of researchers, later claiming that they were too busy to have their hair cut, tested the system by ordering a barber’s chair, which arrived with minimal delay.32 The price paid for access to this extraordinary largesse included unprecedented secrecy, a loss of some personal freedom and the imposition of having virtually all mail vetted by the military censors, though this too was done in secret. Despite the irritations, the scientific climate on the site was more than congenial for its physicists, and for many of them their time there was a highlight of their professional lives. This was made possible mainly by the tactful and effective leadership of Oppenheimer, who seemed to be omnipresent on the site – a tall, slim, flat-footed chain-smoker in a sweat-stained pork-pie hat.

  As Oppenheimer explained to Bohr, the laboratory – near the town of Los Alamos – was the nerve centre of the Manhattan Project but only a small part of a network of sites. About 1,250 miles east of the site was a huge complex at Oak Ridge in Tennessee, a town that had been turned over almost entirely to the production of fissile materials, mainly plutonium and 235U. Its population would ultima
tely rise from three thousand to seventy-five thousand, almost all of them working at – or associated with – one of the town’s facilities, which eventually consumed about a seventh of the electricity generated in the whole of the United States. Among the four facilities then under construction in Oak Ridge was a gaseous diffusion plant of the type favoured by the British, a vast U-shaped facility with arms about half a mile long. A few weeks later, Bohr and his son paid a short visit to this site and saw, as Aage later wrote, ‘almost unbelievable dimensions . . . like a glimpse into a new age’. They saw here that much of the heavy lifting on the project was being done by the chemists and engineers who laboured to produce every speck of fissile material so that the physicists at Site Y could carry out experiments on them.

  Almost as large and impressive as Oak Ridge was another facility, a thousand miles from Los Alamos, on the Columbia River at Hanford, in the north-western state of Washington. This site was devoted entirely to the production of chemicals containing weapons-grade plutonium and was enveloped in even greater secrecy, out of bounds to the Bohrs and to every other member of the British mission except Chadwick.33

  Bohr – now known by his pseudonym, Nicholas Baker – told Oppenheimer that he was more shaken by the vastness of the Manhattan Project than by anything since Rutherford’s discovery of the atomic nucleus, thirty-two years before.34 Nuclear science had previously been the province of physicists and chemists working in a few laboratories with the modest budgets needed to fund desktop experiments. Now, the drive to build nuclear weapons was well on its way to becoming the fourth-largest industry in America. Edward Teller, one of the physicists who had long thought that the Bomb project was viable, was looking forward to telling Bohr ‘I told you so,’ but before he could open his mouth the Dane butted in: ‘You see, I told you it couldn’t be done without turning the whole country into a factory. You have done just that.’35

  Bohr took an interest in the technical work the scientists were doing and he contributed to it, but his main role was to be a kind of father confessor to his colleagues, their ‘Uncle Nick’, as they called him. The switch from curiosity-driven science to mission-driven weapons development had been difficult for many of them, including Bohr’s old friend Otto Frisch, one of the first to understand nuclear fission and coauthor of the memorandum that had kick-started research on the Bomb three years before. Frisch and his former Birmingham colleague Ernest Titterton were the first members of the British team to arrive, seventeen days before Bohr. They were soon joined by others, including James Chadwick, Rudi Peierls and Mark Oliphant, whose reputation as a gabby critic was probably responsible for his being allowed on the site for all of one day, with only limited security clearance (‘no access’).36 Together with their American colleagues, the British scientists were grappling with the challenge of projecting two lumps of fissile material towards each other at high speed to form a critical mass – as Frisch and Peierls had envisaged – after the device had been released by an aircraft. The entire project had turned out to be much more complex and difficult than almost anyone had foreseen. For some of the scientists, the excitement of the challenge eclipsed the horror of the potential consequences of their labours – the ultimate purpose of ‘the gadget’ was to atomise thousands of human beings in a matter of seconds.

  As Oppenheimer later recalled, ‘Bohr at Los Alamos was marvellous . . . he made the enterprise, which often looked so macabre, seem hopeful.’37 The first serious question Bohr put to Oppenheimer about the Bomb was ‘Is it big enough?’ Was it so destructive an explosive that no sane leader would ever be able to use it, for fear that the enemy would retaliate in kind? Oppenheimer may well have told Bohr that even if the fission weapons they were building were not ‘big enough’, then another type of nuclear bomb that his colleague Edward Teller was already contemplating would indeed fit the bill. Teller was thinking about thermonuclear weapons, which use the heat generated by an ordinary fission bomb to release energy by fusing low-mass nuclei. Such weapons, later to be exemplified by the hydrogen bomb, would be far more powerful than any explosive Oppenheimer and his team were then hoping to build.

  Bohr’s optimism was founded in his philosophical approach to the Bomb. It was based on his favourite intellectual idea and tool, the principle of complementarity, which he first set out in 1927 as a way of looking at quantum physics, though he subsequently applied it outside science. He appears never to have published a definition of the general principle, though he made its content reasonably clear – roughly speaking, it says that every intellectual challenge should be viewed in terms of at least one pair of complementary perspectives, neither of which has a monopoly on truth. So, for example, when considering how institutions should develop, it could be argued that the only thing that counts is the preservation of tradition or, alternatively, that fostering innovation is all that matters. Bohr believed that in this and every other case neither extreme is ever wholly correct; rather, both are needed to explore the truth. For him, truth could be glimpsed only stereoscopically, never in perfect focus.

  Bohr used this type of reasoning as he thought about the potential impact of nuclear weapons – they could be seen as a terrible threat to humanity, but also as a boon, which is why he wanted the Bomb to be as big as possible. He also wanted the Allies to be as open as practically feasible about this new military development: Britain and America should inform Russia of the Manhattan Project in order to help achieve a higher level of trust, he believed, as this would help to avoid a post-war conflict as well as a nuclear-arms race.38

  During Bohr’s stay, he made a huge impact on Oppenheimer’s thinking about the weapons he was developing and the effects they might have on global politics after the war. After Oppenheimer and his colleagues had talked with Bohr, it seemed increasingly implausible that Hitler would be able to construct the Bomb before the Allies. That, however, certainly did not mean that work on the Bomb at Site Y would stop – as Oppenheimer’s assistant David Hawkins later recalled, ‘We were committed to building the bomb regardless of German progress.’39 Having recruited the scientists to construct it, only Roosevelt and Churchill would decide how it would be used, as Bohr knew. Yet he had seen no sign that either leader had given deep thought to the significance of the weapon they would soon have at their disposal. This is why he took it upon himself to try to bring some of the same leadership to the new nuclear politics as he had given to the community of physicists twenty years before, during the birth of quantum mechanics, though he was ill equipped for the task.

  He had been preparing the ground for his interventions even before he sailed for the United States. Through Anderson, he had secured an appointment with the British Ambassador in Washington, Lord Halifax, and he also arranged to meet his old acquaintance Felix Frankfurter, a Supreme Court Justice and a friend of Roosevelt.40 At his second meeting with Bohr, at the Court Building on 15 February 1944, Frankfurter disclosed that he knew about the Bomb project, opening the way for Bohr to describe the diplomatic opportunities that he believed the Bomb offered, although he tiptoed around the military secrets. ‘Let us hope that this will be a memorable day,’ Frankfurter said when they parted, hinting that he would raise the matter discreetly with the President.41

  In London, Anderson took the plunge and put Bohr’s ideas on nuclear strategy to Churchill, not mentioning their provenance.42 The Prime Minister’s response was predictably terse, firm and dismissive: when Anderson suggested ‘collaboration’ with the Russians, Churchill circled the word and wrote in the margin ‘on no account’.

  Although fast becoming a close friend of the Great Dane, Anderson chose not to tell him about the rebuff, perhaps because it would almost certainly have taken the wind out of his sails. So Bohr continued to advance his case with impressive vigour, oblivious of the formidable obstacle now ahead of him. During the early Washington spring, he marshalled his thinking in a long report for Anderson with the title ‘Confidential comments on the project exploiting the latest discoveries of
atomic physics for industry and warfare’. Although the document begged for the services of a good editor, his circumlocutions contained a powerfully original argument for thinking about the Manhattan Project as a global opportunity rather than a threat. In the final section, Bohr stressed the long-term importance of his cause:

  Such an initiative, aiming at forestalling a fateful competition about the formidable weapon, need in no way impede the importance of the project for the immediate military objectives, but should serve to uproot any cause for distrust between the powers on whose harmonious collaboration the fate of coming generations will depend.

  About two weeks after Bohr sent his statement to London, he received encouraging news from Frankfurter. He had met with Roosevelt, who told him that the nuclear bomb ‘worried him to death’, assuring Frankfurter that he was receptive to Bohr’s ideas and that ‘he would welcome any suggestion to this purpose from the Prime Minister’. Having spoken with Frankfurter, Bohr understood that he was to act as an emissary of Roosevelt on the need to look again at nuclear policy, so the Great Dane pressed for an urgent meeting with Churchill, with support from his colleagues in Whitehall. Soon, Bohr was packing his bags, preparing to leave the cherry blossom and creature comforts of Washington DC for another stay in dreary, war-torn London.

  Bohr returned to find the door to 10 Downing Street firmly closed against him. Anderson had approached Churchill again in late April, having heard that Roosevelt was ‘giving serious thought’ to the possibilities of international arms control and ‘would not be averse’ to discussing it with him.43 Anderson had even drafted a message to the President, concluding suggestively that the matter ‘seems to me to require deep thought’. Once again, Sir John was rebuffed – ‘I do not think that any such telegram is necessary,’ Churchill replied by return. Anderson said nothing about this to Bohr, who was at a loss to understand why he was not being allowed to see the Prime Minister. The Dane was now more confident of his case: he was now sure that the Soviets were also working on the Bomb, so it was pointless to try to keep it secret from them. The evidence came from his imaginative interpretation of comments in a warm letter he received from Peter Kapitza, formerly one of Rutherford’s favourite ‘boys’, now working in his Soviet homeland.44 Bohr showed the letter to the British security services and, with their agreement, sent a non-committal reply that would soon get him into deep trouble.45