14
Robert Oppenheimer was thirty-eight years old in 1942. He had done by then what Hans Bethe calls “massive scientific work.”1708 He was known and respected as a theoretician throughout the world of physics. Up to the time of the Berkeley summer study, however, few of his peers seem to have thought him capable of decisive leadership. Though he had matured deeply across the decade of the 1930s, his persistent mannerisms, especially his caustic tongue, may have screened his maturity from his colleagues’ eyes. Yet the 1930s shaped Oppenheimer for the work that was now to challenge him.
His distinctive appearance sharpens the memory of an admiring new friend of that decade, a Berkeley professor and translator of French literature named Haakon Chevalier:
[Oppenheimer] was tall, nervous and intent, and he moved with an odd gait, a kind of jog, with a great deal of swinging of his limbs, his head always a little to one side, one shoulder higher than the other. But it was the head that was the most striking: the halo of wispy black curly hair, the fine, sharp nose, and especially the eyes, surprisingly blue, having a strange depth and intensity, and yet expressive of a candor that was altogether disarming. He looked like a young Einstein, and at the same time like an overgrown choir boy.1709
Chevalier’s portrait identifies Oppenheimer’s youthfulness and sensitivity but misses the self-destructiveness: the chain-smoking, the persistent cough persistently ignored, the ravaged teeth, the usually empty stomach assaulted by highly praised martinis and highly spiced food. Oppenheimer’s emaciation suggests he had an aversion to incorporating the world. His body embarrassed him and he seldom allowed himself to appear, as at the beach, undressed. At school he wore gray suits, blue shirts and well-polished black shoes. At home (a small spare apartment at first; later, after his marriage, the elegant house in the Berkeley hills he bought with a check the day he first toured it) he preferred jeans and blue chambray work shirts, the jeans hung on his narrow hips with a wide Western silver-buckled belt. It was not a common look in the 1930s—he had picked it up in New Mexico—and it was another detail that made him seem different.
Women thought him handsome and dashing. Before a party he might send gardenias not only to his own date but to his friends’ dates as well. “He was great at a party,” a female acquaintance of his later adulthood comments, “and women simply loved him.”1710His unfailing attentiveness probably elicited that admiration: “He was always,” writes Chevalier, “without seeming effort, aware of, and responsive to, everyone in the room, and was constantly anticipating unspoken wishes.”1711
Men he could antagonize or amuse. Edward Teller first met Oppenheimer in 1937. The meeting, Teller says, was “painful but characteristic. On the evening I was to talk at a Berkeley colloquium, he took me out to a Mexican restaurant for dinner. I didn’t have the practice in speaking that I’ve had since, and I was already a little nervous. The plates were so hot, and the spices were so hot—as you might suspect if you knew Oppenheimer—and his personality was so overpowering, that I lost my voice.”1712 Emilio Segrè notes that Oppenheimer “sometimes appeared amateurish and snobbish.” Out of curiosity in 1940, while visiting Berkeley to deliver a lecture, Enrico Fermi attended a seminar one of Oppenheimer’s protégés led in the master’s style. “Emilio,” Fermi joked afterward with Segrè, “I am getting rusty and old. I cannot follow the highbrow theory developed by Oppenheimer’s pupils anymore. I went to their seminar and was depressed by my inability to understand them. Only the last sentence cheered me up; it was: ‘and this is Fermi’s theory of beta decay.’ ” Although Segrè found Oppenheimer “the fastest thinker I’ve ever met,” with “an iron memory . . . brilliance and solid merits,” he also saw “grave defects” including “occasional arrogance . . . [that] stung scientific colleagues where they were most sensitive.” “Robert could make people feel they were fools,” Bethe says simply.1713 “He made me, but I didn’t mind. Lawrence did. The two disagreed while they were both still at Berkeley.1714 I think Robert would give Lawrence a feeling that he didn’t know physics, and since that is what cyclotrons are for, Lawrence didn’t like it.” Oppenheimer recognized the habit without diagnosing it in a letter to his younger brother Frank: “But it is not easy—at least it is not easy for me—to be quite free of the desire to browbeat somebody or something.”1715 He called the behavior “beastliness.” It did not win him friends.
Oppenheimer’s mother died after a long battle with leukemia in late 1931; that was when he announced himself to Herbert Smith, his former Ethical Culture teacher, to be “the loneliest man in the world.”1716 His father died suddenly of a heart attack in 1937. The two deaths frame the beginning years of the unworldly physicist’s discovery of the suffering in the world. Later he testified to the surprise of that discovery:
My friends, both in Pasadena and in Berkeley, were mostly faculty people, scientists, classicists, and artists. I studied and read Sanskrit with Arthur Ryder. I read very widely, mostly classics, novels, plays, and poetry; and I read something of other parts of science. I was not interested in and did not read about economics or politics. I was almost wholly divorced from the contemporary scene in this country. I never read a newspaper or a current magazine like Time or Harper’s; I had no radio, no telephone; I learned of the stock market crash in the fall of 1929 only long after the event; the first time I ever voted was in the Presidential election of 1936.1717, 1718 To many of my friends, my indifference to contemporary affairs seemed bizarre, and they often chided me with being too much of a highbrow. I was interested in man and his experience; I was deeply interested in my science; but I had no understanding of the relations of man to his society. . . .
Beginning in late 1936, my interests began to change.
Oppenheimer reports three reasons for the change. “I had had a continuing, smouldering fury about the treatment of the Jews in Germany,” he mentions first. “I had relatives there, and was later to help in extricating them and bringing them to this country.” They arrived only a few days after his father’s death and he and Frank volunteered responsibility for them.
Second, says Oppenheimer, “I saw what the Depression was doing to my students.” Philip Morrison, one of the wittiest of the young theoreticians, polio-crippled and poor, remembers in compensation the “very grave, very profound involvement in physics, the love of the whole thing, which we all had in those days.”1719 Oppenheimer could take his admiring students to dinner; he was unable to find them jobs. “And through them,” he testifies, “I began to understand how deeply political and economic events could affect men’s lives.1720 I began to feel the need to participate more fully in the life of the community.”
He had no framework yet. A woman would help him with that, her involvement the third reason he gives for his entry into the world: Jean Tatlock, the lithe, chiaroscuro daughter of an anti-Semite Berkeley medievalist. “In the autumn [of 1936], I began to court her, and we grew close to each other. We were at least twice close enough to marriage to think of ourselves as engaged.” Tatlock was bright, passionate and compassionate, frequently depressed; their relationship was an ocean of storms. But so were Tatlock’s other commitments. “She told me about her Communist Party memberships; they were on again, off again affairs, and never seemed to provide for her what she was seeking.” The couple began to move together among what he calls “leftwing friends. . . . I liked the new sense of companionship, and at the time felt that I was coming to be part of the life of my time and country.”1721 He was taken with the causes of the Loyalists in the Spanish Civil War and the migrant workers in California, to both of which he contributed time and money. He read Engels and Feuerbach and all of Marx, finding their dialectics less rigorous than his taste: “I never accepted Communist dogma or theory; in fact, it never made sense to me”.1722
He met his wife, Kitty, in the summer of 1939 in Pasadena. She was petite and dark, with a broad, high forehead, brown eyes, prominent cheekbones and a wide, expressive mouth. On the rebound she had married a young British physician, “Dr. [Stewart] Harrison, who was a friend and associate of the [Richard] Tolmans, [Charles C.] Lauritsens, and others of the California Institute of Technology faculty [Harrison was doing cancer research]. I learned of her earlier marriage to Joe Dallet, and of his death fighting in Spain. He had been a Communist Party official, and for a year or two during their brief marriage my wife was a Communist Party member. When I met her I found in her a deep loyalty to her former husband, a complete disengagement from any political activity, and a certain disappointment and contempt that the Communist Party was not in fact what she had once thought it was.”1723 The involvement was apparently immediate and intense.
Probably with his wife’s encouragement, but certainly with his own growing good sense, Oppenheimer began to jettison political commitments that had come to seem parochial. “I went to a big Spanish relief party the night before Pearl Harbor,” he testifies in example, “and the next day, as we heard the news of the outbreak of war, I decided that I had had about enough of the Spanish cause, and that there were other and more pressing crises in the world.”1724, 1725 He was willing similarly to abandon the American Association of Scientific Workers at Lawrence’s insistence in order to help, as he supposed, to beat the Nazis to the atomic bomb.
By then, says Bethe, though Oppenheimer had been a poor teacher when he began, pitching quantum theory well above his students’ untrained range, he had “created the greatest school of theoretical physics that the United States has ever known.” Bethe’s explanation for that evolution reveals the seedbed of Oppenheimer’s later administrative leadership:
Probably the most important ingredient he brought to his teaching was his exquisite taste. He always knew what were the important problems, as shown by his choice of subjects. He truly lived with those problems, struggling for a solution, and he communicated his concern to his group. . . . He was interested in everything, and in one afternoon [he and his students] might discuss quantum electrodynamics, cosmic rays, electron pair production and nuclear physics.
During the same period Oppenheimer’s clumsiness with experiment evolved to appreciation and he consciously mastered experimental work—hands off. “He began to observe, not manipulate,” a former student notes. “He learned to see the apparatus and to get a feeling of its experimental limitations. He grasped the underlying physics and had the best memory I know of. He could always see how far any particular experiment would go. When you couldn’t carry it any farther, you could count on him to understand and to be thinking about the next thing you might want to try.”1726
It remained for Oppenheimer to learn to control his “beastliness” and submerge his mannerisms. But he was always a quick study. Significantly, he was least convoluted, most direct, least mannered, most natural living simply at his unadorned ranch in the Pecos Valley high in the Sangre de Cristo Mountains of northern New Mexico.
Oppenheimer first met General Leslie R. Groves when Groves came to Berkeley from Chicago on his initial inspection tour early in October 1942. They attended a luncheon given by the president of the university; afterward they talked. Oppenheimer had already discussed the need for a fast-neutron laboratory at the Met Lab technical council meeting on September 29.1727 He envisioned more responsibilities for that laboratory than basic fission studies, as he testified after the war:
I became convinced, as did others, that a major change was called for in the work on the bomb itself. We needed a central laboratory devoted wholly to this purpose, where people could talk freely with each other, where theoretical ideas and experimental findings could affect each other, where the waste and frustration and error of the many compartmentalized experimental studies could be eliminated, where we could begin to come to grips with chemical, metallurgical, engineering, and ordnance problems that had so far received no consideration.1728
Memory compresses the laboratory’s evolution here, however; Oppenheimer is not likely to have discussed eliminating Groves’ cherished compartmentalization at their first meeting. To the contrary, he goes on to say, the two men first considered making the laboratory “a military establishment in which key personnel would be commissioned as officers,” and he carried the idea far enough before he left Berkeley to visit a nearby military post to begin the process of commissioning.1729
Groves remembers that his “original impression gained from our first conversation in Berkeley” was that a central laboratory was a good idea; he felt strongly that “the work [of bomb design] should be started at once in order that one part of our operation, at any rate, could progress at what I hoped would be a comfortable pace.”1730, 1731 His immediate concern was leadership; he believed that the right man at the helm could sail even the most ungovernable boat. Ernest Lawrence would have been Groves’ first choice, but the general doubted if anyone else could make electromagnetic isotope separation work. Compton had his hands full in Chicago. Harold Urey was a chemist. “Outside the project there may have been other suitable people, but they were all fully occupied on essential work, and none of those suggested appeared to be the equal of Oppenheimer.”1732 Groves had already sized up his man.
“It was not obvious that Oppenheimer would be [the new laboratory’s] director,” Bethe notes. “He had, after all, no experience in directing a large group of people. The laboratory would be devoted primarily to experiment and to engineering, and Oppenheimer was a theorist.”1733 Worse—in the eyes of the project leaders, Nobel laureates all—he had no Nobel Prize to distinguish him. There was also what Groves calls the “snag” of Oppenheimer’s left-wing background, which “included much that was not to our liking by any means.”1734 Groves had not yet wrested control of Manhattan Project security from Army counterintelligence, and that organization adamantly refused to clear someone whose former fiancée, wife, brother and sister-in-law had all been members of the Communist Party once and perhaps, gone underground, still were.
The general wanted Oppenheimer anyway. “He’s a genius,” Groves told an interviewer off the record immediately after the war. “A real genius. While Lawrence is very bright he’s not a genius, just a good hard worker. Why, Oppenheimer knows about everything. He can talk to you about anything you bring up.1735 Well, not exactly. I guess there are a few things he doesn’t know about. He doesn’t know anything about sports.”
Groves proposed Oppenheimer’s name to the Military Policy Committee. It balked. “After much discussion I asked each member to give me the name of a man who would be a better choice. In a few weeks it became apparent that we were not going to find a better man; so Oppenheimer was asked to undertake the task.”1736 The physicist demurred later that he was chosen “by default. The truth is that the obvious people were already taken and that the Project had a bad name.”1737 Rabi would come to think that “it was a real stroke of genius on the part of General Groves, who was not generally considered to be a genius, to have appointed him,” but at the time it seemed “a most improbable appointment. I was astonished.”1738 Groves on his way from Chicago to New York asked Oppenheimer on October 15, 1942, to ride on the train with him as far as Detroit to discuss the appointment. The two men met with Vannevar Bush in Washington on October 19.1739 That long meeting was apparently decisive. Security questions would have to wait.
The next problem was where to locate the new laboratory. Already at his first meeting with Oppenheimer in Berkeley, Groves had stressed the need for isolation; however much or little the scientists who gathered at the new center would be allowed to talk to each other, the general intended to divide them away from the populace. “For this reason,” Oppenheimer wrote his Illinois colleague John H. Manley in mid-October, “some rather far reaching geographical change in plans seems to be in the cards.” (In the same letter Oppenheimer proposed “start[ing] now on a policy of absolutely unscrupulous recruiting of anyone we can lay hands on.”1740, 1741 He wanted the best he could get, and soon asked Groves for the likes of Bethe, Segrè, Serber and Teller.)
Site Y, as the hypothetical laboratory was initially called, needed good transportation, an adequate supply of water, a local labor force and a moderate climate for year-round construction and for experiment conducted outdoors. In his memoirs Groves lists safety as the primary reason he insisted on isolation—“so that nearby communities would not be adversely affected by any unforeseen results from our activities”—but the high steel fence topped with triple strands of barbed wire that eventually surrounded the laboratory was clearly not designed to confine explosions. Groves was in the midst of selecting sites for Manhattan Project production centers; the difference between his criteria for those locations and his criteria for Site Y was that at the bomb-design laboratory “we were faced with the necessity of importing a group of highly talented specialists, some of whom would be prima donnas, and of keeping them satisfied with their working and living conditions.”1742 If that in fact was Groves’ intention, it was one of the few wartime goals he failed to achieve.1743
The general assigned the task of identifying a suitable location for the laboratory to Major John H. Dudley of the Manhattan Engineer District. Groves gave Dudley criteria more specific than satisfying prima donnas: room for 265 people, location at least two hundred miles from any international boundary but west of the Mississippi, some existing facilities, a natural bowl with the hills nearby that shaped the bowl so that fences might be strung on top and guarded. Traveling by air, rail, auto, jeep and horse through most of the American Southwest, Dudley found the perfect place: Oak City, Utah, “a delightful little oasis in south central Utah.”1744 But to claim it the Army would have had to evict several dozen families and remove a large area of farmland from production. Dudley thereupon recommended his second choice: Jemez Springs, New Mexico, a deep canyon about forty miles northwest of Santa Fe on the western slope of the Jemez Mountains—“a lovely spot,” Oppenheimer thought in early November before he toured it, “and in every way satisfactory.”1745
When the newly appointed director arrived on November 16 to inspect the Jemez Springs location with Dudley and Edwin McMillan, who was helping start the laboratory, he changed his mind. The canyon felt confining; Oppenheimer knew the region’s grand scenic vistas and decided he wanted a laboratory with a view. McMillan also remembers expressing “considerable reservations about this site”:1746
We were arguing [with Dudley] when General Groves showed up. This had been planned. He would come in sometime in the afternoon and receive our report. As soon as Groves saw the site he didn’t like it; he said, “This will never do.” . . . At that point Oppenheimer spoke up and said “if you go on up the canyon you come out on top of the mesa and there’s a boys’ school there which might be a usable site.”
Oppenheimer proposed the boys’ school site, grouses Dudley, “as though it was a brand new idea.” Dudley had already scouted the mesa twice, rejecting it because it failed to meet Groves’ criteria. But a mesa is an inverted bowl, its perimeter similarly fencible. And the first requirement was to make the longhairs happy. “As I . . . knew the roads (or trails),” Dudley says sardonically, “ . . . we drove directly there.”1747
“The school was called Los Alamos,” the daughter of its founder writes, “after the deep canyon which bordered the mesa to the south and which was groved with cottonwood trees along the sandy trickle of its stream.”1748 Ashley Pond, the founder, had been a sickly boarding-school boy sent West for his health, like Oppenheimer, who returned to New Mexico in later adulthood when his father died and left him with independent means. He opened the Los Alamos Ranch School on the 7,200-foot mesa in 1917. It was organized to invigorate pale scions, as Pond had been invigorated: boys slept on unheated porches of a chinked-log dormitory and wore shorts in winter snow; each was assigned a horse to ride and groom. It was, Emilio Segrè writes, “beautiful and savage country”: the dark Jemez Mountains to the west that formed the higher rim of the Jemez Caldera, the slumped cone of the old volcano of which Los Alamos was eroded tuffaceous spill; precipitously down from the mesa eastward the valley of the Rio Grande, “hot and barren” except for the green meander of the river, writes Laura Fermi, with “sand, cacti, a few piñon trees hardly rising above the ground, and space, immense, transparent, with no fog or moisture”; farther east the wall of the Rocky Mountains as that range extends south into New Mexico to form the Sangre de Cristo, reversing hue from green to red progressively at sunset.1749, 1750 “I remember arriving [at Los Alamos],” McMillan continues of that first inspection, “and it was late in the afternoon. There was a slight snow falling. . . . It was cold and there were the boys and their masters out on the playing fields in shorts. I remarked that they really believed in hardening up the youth. As soon as Groves saw it, he said, in effect, ‘This is the place.’ ”1751
“My two great loves are physics and desert country,” Robert Oppenheimer had written a friend once; “it’s a pity they can’t be combined.”1752 Now they would be.
Leo Szilard, urban man, habitué of hotel lobbies, took a different view of the location when he heard about it. “Nobody could think straight in a place like that,” he told his Met Lab colleagues. “Everybody who goes there will go crazy.”1753 The Corps of Engineers’ appraisal prepared on November 21 describes a large forested site thirty-five miles by road northwest of Santa Fe with no gas or oil lines, one one-wire Forest Service telephone, average annual precipitation of 18.53 inches and an annual range of temperatures from —12° to 92°F.1754 The land and improvements, including the boys’ school with its sixty horses, two tractors, two trucks, fifty saddles, eight hundred cords of firewood, twenty-five tons of coal and sixteen hundred books, were worth $440,000. The school was willing to sell. The Manhattan Project acquired its scenic laboratory site.
Groves convinced the University of California to serve as contractor to operate the secret installation. Construction—of cheap, barracks-like buildings not intended to outlast the war, with coal-burning stoves and no sidewalks on which to escape the mire of spring and autumn mud—began almost immediately. “What we were trying to do,” writes John Manley, the University of Illinois physicist working with Oppenheimer then, “was build a new laboratory in the wilds of New Mexico with no initial equipment except the library of Horatio Alger books or whatever it was that those boys in the Ranch School read, and the pack equipment that they used going horseback riding, none of which helped us very much in getting neutron-producing accelerators.”1755 Robert R. Wilson, a young Berkeley Ph.D. teaching at Princeton, went up to Harvard for Oppenheimer and negotiated with Percy Bridgman for the Harvard cyclotron; Wisconsin would contribute two Van de Graaffs; from other laboratories, including Berkeley and the University of Illinois, Manley scavenged other gear. In the meantime Oppenheimer crisscrossed the country recruiting:
The prospect of coming to Los Alamos aroused great misgivings.1756 It was to be a military post; men were asked to sign up more or less for the duration; restrictions on travel and on the freedom of families to move about would be severe. . . . The notion of disappearing into the New Mexico desert for an indeterminate period and under quasi-military auspices disturbed a good many scientists, and the families of many more. But there was another side to it. Almost everyone realized that this was a great undertaking. Almost everyone knew that if it were completed successfully and rapidly enough, it might determine the outcome of the war. Almost everyone knew that it was an unparalleled opportunity to bring to bear the basic knowledge and art of science for the benefit of his country. Almost everyone knew that this job, if it were achieved, would be a part of history. This sense of excitement, of devotion and of patriotism in the end prevailed. Most of those with whom I talked came to Los Alamos.
One of the most tough-minded, I. I. Rabi, did not. His reasons are revealing. He continued developing radar at the Radiation Laboratory at MIT. “Oppenheimer wanted me to be the associate director,” he told an interviewer many years later. “I thought it over and turned him down. I said, ‘I’m very serious about this war. We could lose it with insufficient radar.’ ”1757 The Columbia physicist thought radar more immediately important to the defense of his country than the distant prospect of an atomic bomb. Nor did he choose to work full time, he told Oppenheimer, to make “the culmination of three centuries of physics” a weapon of mass destruction.1758 Oppenheimer responded that he would take “a different stand” if he thought the atomic bomb would serve as such a culmination. “To me it is primarily the development in time of war of a military weapon of some consequence.”1759 Either Oppenheimer had not yet thought his way through to a more millenarian view of the new weapon’s implications or he chose to avoid discussing those implications with Rabi. He asked Rabi only to participate in an inaugural physics conference at Los Alamos in April 1943 and to help convince others, particularly Hans Bethe, to sign on. Eventually Rabi would come and go as a visiting consultant, one of the very few exceptions to Groves’ compartmentalization and isolation rules.
Oppenheimer talked to the Bethes in Cambridge in snowy New England December; they questioned him at length about the life they would be asked to lead. Extracts from his letter of response sketch the invention of an instant community: “Laboratory . . . town . . . utilities, schools, hospitals . . . a sort of city manager . . . city engineer . . . teachers . . . M.P. camp . . . a laundry . . . two eating places . . . a recreation officer . . . libraries, pack trips, movies . . . bachelor apartments . . . a so-called Post Exchange . . . a vet . . . barbers and such like . . . a cantina where we can have beer and cokes and light lunches.” The Bethes’ best guarantee of satisfaction, Oppenheimer concluded, “is in the great effort and generosity that . . . Groves [has] brought to setting up this odd community and in [Groves’] evident desire to make a real success of it. In general [he is] not interested in saving money, but . . . in saving critical materials, in cutting down personnel, and in doing nothing which would attract Congressional attention to our hi-jinks.” He chose not to mention the security arrangements, in the development of which he was participating: the perimeter fence, the pass controls, the virtual elimination of telephones (“Oppenheimer’s idea was one telephone for himself,” says Dudley, “one for the post commander, and any volume business would go out over a teletype.”1760, 1761 ). By March Teller found Bethe taking “a very optimistic view, and there was no need whatever to persuade him to come.”1762
Teller felt underemployed in Chicago and was eager to move to the new laboratory. John Manley asked him to write a prospectus to help with recruiting, which Teller sent to Oppenheimer in early January. During the Berkeley summer study the two men had begun what another participant judged a “mental love affair.”1763, 1764 Teller “liked and respected Oppie enormously. He kept wanting to talk about him with others who knew him, kept bringing up his name in conversation.” Bethe noticed then and later that despite their many outward differences Teller and Oppenheimer were “fundamentally . . . very similar.1765 Teller had an extremely quick understanding of things, so did Oppenheimer. . . . They were also somewhat alike in that their actual production, their scientific publications, did not measure up in any way to their capacity. I think Teller’s mental capacity is very high, and so was Oppenheimer’s but, on the other hand, their papers, while they included some very good ones, never reached really the top standards. Neither of them ever came up to the Nobel Prize level. I think you just cannot get to that level unless you are somewhat introverted.” (Luis Alvarez, the 1968 physics Nobel laureate, disagrees, at least where Oppenheimer is concerned.1766 He believes Oppenheimer would have won a Nobel Prize for his astrophysical work if he had lived long enough to see his predictions concerning exotic stellar objects—neutron stars, black holes—confirmed, as they have been, by discovery.) Both Oppenheimer and Teller wrote poetry; Oppenheimer pursued literature as Teller pursued music; and for a time in 1942 and 1943 the Hungarian apparently admired the older and socially more sophisticated New Yorker and hoped to count him for an ally.
As Oppenheimer traveled the country recruiting he discovered to his surprise that few of his colleagues were attracted to the notion of joining the Army. It fell to Rabi and his Rad Lab colleague Robert F. Bacher, during the weeks before Rabi decided to stay in Cambridge, to lead the revolt. The necessity of “scientific autonomy” was one crucial reason they cited for resisting militarization, Oppenheimer wrote Conant at the beginning of February 1943, and they insisted as a corollary that although “the execution of the security and secrecy measures should be in the hands of the military . . . the decision as to what measures should be applied must be in the hands of the Laboratory.” On that point Oppenheimer concurred, “because I believe it is the only way to assure the cooperation and the unimpaired morale of the scientists.” The stakes were higher than simply losing Rabi and Bacher, Oppenheimer told Conant: “I believe that the solidarity of physicists is such that if these conditions are not met, we shall not only fail to have the men from M.I.T with us, but that many men who have already planned to join the new Laboratory will reconsider their commitments or come with such misgivings as to reduce their usefulness.” A rebellion, he concluded, would mean “a real delay in our work.”1767
Groves had wanted the scientists commissioned as a security measure and because their work might be hazardous. He was hardly interested in the politics of the question, but delay was unthinkable. He compromised. Conant wrote a letter, co-signed by Groves, that Oppenheimer could use in recruiting; it allowed the new laboratory civilian administration and civilian staff until the time of hazardous large-scale trials. Then anyone who wanted to stay would have to accept a commission (a provision Groves chose later not to pursue). The Army would administer the community it was building around the laboratory. Laboratory security would be Oppenheimer’s responsibility, and he would report to Groves.
Robert Oppenheimer thus acquired for Los Alamos what Leo Szilard had not been able to organize in Chicago: scientific freedom of speech. The price the new community paid, a social but more profoundly a political price, was a guarded barbed-wire fence around the town and a second guarded barbed-wire fence around the laboratory itself, emphasizing that the scientists and their families were walled off where knowledge of their work was concerned not only from the world but even from each other. “Several of the European-born were unhappy,” Laura Fermi notes, “because living inside a fenced area reminded them of concentration camps.”1768
* * *
The heavy-water installation at Vemork in southern Norway became a target of British sabotage operations in the winter of 1942–43. The British had been planning to send in two glider-loads of demolition experts, thirty-four trained volunteers; when Groves requested Allied action soon after his appointment to administer the Manhattan Project they moved ahead to comply. An advance party of four Norwegian commandos parachuted into the Rjukan area on October 18 to prepare the way, but bad planning and bad weather brought disaster to the gliders on the night of November 19 when they crossed the North Sea from Scotland; both crashed in Norway, one into a mountainside, and the fourteen men who survived the separate disasters were captured by German occupation forces and executed the same day.
R. V. Jones, an Oxford protégé of Cherwell who was now director of intelligence for the British Air Staff, then had “one of the most painful decisions that I had to make” —whether to send another demolition party after the first. “I reasoned that we had already decided, before the tragedy of the first raid and therefore free from sentiment, that the heavy water plant must be destroyed; casualties must be expected in war, and so if we were right in asking for the first raid we were probably right in asking that it be repeated.”
This time six men, Norwegians native to the region and trained as Special Forces, parachuted onto a frozen lake thirty miles northwest of Vemork on February 16, 1943, the night of a full moon.1769 “Here lay the Hardanger Vidda,” one of them, Knut Haukelid, writes of the high plateau that surrounded the lake, “the largest, loneliest and wildest mountain area in northern Europe.” The men wore white jumpsuits over British Army uniforms and parachuted with skis, supplies, a shortwave radio and eighteen sets of plastic explosives, one for each of the eighteen stainless-steel electrolysis cells of the High Concentration Plant—which happened to have been designed by a refugee physical chemist, Lief Tronstad, who was now responsible to the Norwegian High Command in London for intelligence and sabotage. Haukelid, a powerfully built mountaineer, says they weathered “one of the worst storms I have ever experienced in the mountains” to rendezvous some days later with the four Norwegians of the original advance party, who had been forced to hide out on the barren Hardanger Vidda and were malnourished and weak.1770, 1771, 1772 The new arrivals fattened up their compatriots while one of them skied on to Rjukan to gather the latest information about the plant. He returned to report minefields laid around the obvious approaches, guards on the suspension bridge that crossed the sheer gorge above the shelf on which the hydrochemical facility was built but only fifteen German soldiers on duty despite the forewarning of the failed glider attack. The factory itself was fitted with searchlights and guarded with machine guns.
The commandos set out mid-evening on Saturday, February 27, leaving one man behind to guard the radios. They carried cyanide capsules and agreed that if anyone was wounded he would take his own life rather than allow himself to be captured and risk betraying his comrades. They had camped high on the mountain across the gorge from the plant, which was located to take advantage of the fall of water from the lake that fed it, Tinnsjö. “Halfway down we sighted our objective for the first time, below us on the other side. The great seven-storey factory building bulked large on the landscape. . . . [The wind] was blowing fairly hard, but nevertheless the hum of the machinery came up to us through the ravine. We understood how the Germans could allow themselves to keep so small a guard there. The colossus lay like a mediaeval castle, built in the most inaccessible place, protected by precipices and rivers.”1773
They crashed down through soft snow all the way to the bottom of the gorge, crossed the frozen river, climbed up toward the plant on the other side. Above at the elevation of the shelf was a seldom-used railroad siding leading into the compound that they hoped the Germans had chosen not to mine. “It was a dark night and there was no moon,” Haukelid remembers. The searchlights were kept turned off and the high wind “drowned all the noise we made. Half an hour before midnight we came to a snow-covered building five hundred yards from Vemork, where we ate a little chocolate and waited for the change of sentries.”1774 They divided into two groups, a demolition party and a covering party. “We were well armed: five tommy-guns among nine men, and everyone had a pistol, a knife and hand grenades.”1775
In an hour, time for the sentries to settle, they attacked. Haukelid in the covering party led the way. With bolt cutters they snipped “the thin little iron chain which barred the way to one of the most important military objectives in Europe.”1776 The covering party dispersed to its prearranged positions—Haukelid and one other man took up posts twenty yards from the Wehrmacht barracks, a flimsy wooden building they saw they could easily shoot through—and the demolition party moved ahead. The doors on the ground floor of the plant were locked, but Tronstad in London had identified for the commandos a cable intake that they could crawl along that led directly to the heavy-water facility. Two men looked for some other entrance while two disappeared into the cable intake.
After what seemed to Haukelid an interminable delay he heard an explosion, “but an astonishingly small, insignificant one. Was this what we had come over a thousand miles to do?” The guards were slow to check; only one German soldier appeared and seemed not to realize what had happened; he tried the doors to the plant, found them locked, looked to see if snow falling from the mountain above had detonated a land mine and returned to his quarters.1777 The Norwegians moved out fast. They had descended to the river before the sirens began to sound.
The operation was successful. No one was injured on either side. All eighteen cells had been blown open, spilling nearly half a ton of heavy water into the drains. Not only would the plant require weeks to repair; because it was a cascade, pumping water of increasing deuterium concentration from one cell to the next, it would need almost a year of operation after repair simply to reach equilibrium again on its own and begin producing. General Nikolaus von Falkenhorst, the commander in chief of the occupying German Army in Norway, called the Vemork attack “the best coup I have ever seen.”1778 Whatever German physicists might be doing with heavy water, they would do it more slowly now.
* * *
In Japan both the Army Air Force and the Imperial Navy had moved separately since 1941 to promote atomic bomb research.1779 The Riken, Yoshio Nishina’s prestigious Tokyo laboratory, primarily served the Army, exploring the theoretical possibilities of U235 separation by way of the gaseous barrier diffusion, gaseous thermal diffusion, electromagnetic and centrifuge processes. In the spring of 1942 the Navy committed itself to developing nuclear power for propulsion:
The study of nuclear physics is a national project.1780 Research in this field is continuing on a broad scale in the United States, which has recently obtained the services of a number of Jewish scientists, and considerable progress has been made. The objective is the creation of tremendous amounts of energy through nuclear fission. Should this research prove successful, it would provide a stupendous and dependable source of power which could be used to activate ships and other large pieces of machinery. Although it is not expected that nuclear energy will be realized in the near future, the possibility of it must not be ignored. The Imperial Navy, accordingly, hereby affirms its determination to foster and assist studies in this field.
Soon after that nonviolent affirmation, however, the Naval Technological Research Institute appointed a secret committee of leading Japanese scientists—corresponding to the U.S. National Academy of Sciences committee—to meet monthly to follow research progress until it could report decisively for or against a Japanese atomic bomb. The committee included Nishina, who was forthwith elected chairman. An elderly appointee was Hantarō Nagaoka, whose Saturnian atomic model had nearly anticipated Ernest Rutherford’s planetary model in the early years of the century.
The Navy committee met first on July 8 with the Navy’s chief technical officers at an officers’ club at Shiba Park in Tokyo. It noted that the United States was probably working on a bomb and agreed that whether and how soon Japan could produce such a weapon was as yet uncertain. To the task of answering those questions the Navy appropriated 2,000 yen, about $4,700, somewhat less than the Uranium Committee had summoned from the U.S. Treasury at Edward Teller’s request at the beginning of the American program in 1939.
Nishina hardly participated in the Navy committee meetings. The fact that he was already working for the Army probably constrained him; the two services, both of which were responsible directly to the Emperor without detour through the civilian government, operated far more independently than their American counterparts and were increasingly bitter rivals. Nishina was coming to conclusions of his own, however, and at the end of 1942, when the Navy committee began to report discouragement, he met privately with a young cosmic-ray physicist in his laboratory, Tadashi Takeuchi, told his young colleague he meant to carry forward isotope separation studies and asked him to help. Takeuchi agreed.
Between December 1942 and March 1943 the Navy committee organized a ten-session physics colloquium to work through to a decision. By then it was understood that a bomb would necessitate locating, mining and processing hundreds of tons of uranium ore and that U235 separation would require a tenth of the annual Japanese electrical capacity and half the nation’s copper output. The colloquium concluded that while an atomic bomb was certainly possible, Japan might need ten years to build one. The scientists believed that neither Germany nor the United States had sufficient spare industrial capacity to produce atomic bombs in time to be of use in the war.
After the final March 6 meeting the Navy representative at the colloquium reported discouragement: “The best minds of Japan, studying the subject from the point of view of their respective fields of endeavor as well as from that of national defense, came to a conclusion that can only be regarded as correct. The more they considered and discussed the problem, the more pessimistic became the atmosphere of the meeting.”1781 As a result the Navy dissolved the committee and asked its members to devote themselves to more immediately valuable research, particularly radar.
Nishina continued isotope studies for the Army, deciding on March 19 to focus on thermal diffusion as the only practical separation technology at a time of increasing national shortages. He spoke to his staff of processing several hundred tons of uranium after first building laboratory-scale diffusion apparatus. He envisioned a major program run in parallel, as the Manhattan Project was beginning to be, with weapon design and development proceeding simultaneously with U235 production.
Meanwhile a different branch of the Navy, the Fleet Administration Center, sponsored a new project in atomic bomb development at the University of Kyoto, where Tokutaro Hagiwara had made his startling early prediction of the possibility of a thermonuclear explosive. The university won support in 1943 to the extent of 600,000 yen—nearly $1.5 million—much of which it budgeted to build a cyclotron.
* * *
Robert Oppenheimer moved to Santa Fe with a small team of aides on March 15, 1943, brisk early spring. Scientists and their families arrived by automobile and train during the next four weeks. Not much was ready on the mesa, which they began to call the Hill. Groves wanted no breaches of security in the lobbies of Santa Fe hotels; the Army commandeered guest ranches in the area for quarters suitably remote and bought up Santa Fe’s feeble stock of used cars and jitneys to serve as transportation through ruts and mud up and down the terrifying unbarricaded dirt switchback of the mesa access road. After flat tires and mirings, hours could be short on the Hill. Box lunches assembled in Santa Fe gave cold comfort when the delivery truck made it through.
The hardships only mattered because they slowed the work. Oppenheimer had sold it as work that would end the war to end all wars and his people believed him. The unit of measurement for wasted hours was therefore human lives. Construction crews unwilling to vary the specifications of a laboratory door or hang an unauthorized shelf initially bore the brunt of the scientists’ impatience. John Manley remembers inspecting the chemistry and physics building. It needed a basement at one end for an accelerator and a solid foundation at the other end for the two Van de Graaffs—which end for which was unimportant. Rather than adjust the construction plans for terrain the contractor had drilled the basement from solid rock and used the rock debris as fill for the foundation. “This was my introduction to the Army Engineers.”1782
Fuller Lodge, a Ranch School hall elegantly assembled of monumental hand-hewn logs, was kept to serve as a dining room and guest house. The pond south of the lodge—predictably named Ashley Pond after the Ranch School’s founder—offered winter ice-skating and summer canoeing and the easeful harmonic wakes of swimming ducks. The engineers preserved the stone icehouse beside the pond that the school had used to store winter cuttings of ice and the row of tree-shaded faculty residences northeast of the lodge. Across the dirt main road that divided the mesa south of the pond the Tech Area went up in a style the Army called modified mobilization: plain one-story buildings like elongated barracks with clapboard sides and shingled roofs. T Building would house Oppenheimer and his staff and the Theoretical Physics Division; behind T, connected by a covered walkway, would be the much longer chemistry and physics building with its Van de Graaffs; behind that the laboratory shops. Farther south near the rim of the mesa above Los Alamos canyon contractors would hammer up a cryogenics laboratory and the building that would shelter Harvard’s cyclotron. West and north of the Tech Area the first two-story, four-unit family apartments, painted drab green, urbanized last year’s pastures and fields; more apartments, and dormitories for the unmarried, would follow.
At the beginning of April Oppenheimer assembled the scientific staff—“about thirty persons” at that point of the hundred scientists initially hired, says Emilio Segrè, who was one among them—for a series of introductory lectures.1783 Robert Serber, thin and shy, delivered the lectures with authority despite the distraction of a lisp; they summed up the conclusions of the Berkeley summer study and incorporated the experimental fast-fission work of the past year. Edward U. Condon, the crew-cut, Alamogordoborn theoretician from Westinghouse whom Oppenheimer had chosen for associate director, revised his notes of Serber’s lectures into the new laboratory’s first report, a document called the Los Alamos Primer that was subsequently handed to all new Tech Area arrivals cleared for Secret Limited access.1784 In twenty-four mimeographed pages the Primer defined the laboratory’s program to build the first atomic bombs.
Serber’s lectures startled the chemists and experimental physicists whom compartmentalization had kept in the dark; the scientists’ euphoria at finally learning in detail what they had only previously guessed or heard hinted measures the extent to which secrecy had contorted their emotional commitment to the work. Now, following the lead of their mentors—their average age was twenty-five; Oppenheimer, Bethe, Teller, McMillan, Bacher, Segrè and Condon were older men—they could apply themselves at last with devotion. In that heady new freedom they seldom noticed the barbed wire. Similarly confined but kept uninformed because Oppenheimer and Groves decided it so, the wives served harder time.
“The object of the project,” Condon summarizes what Serber told the scientists, “is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast neutron chain reaction in one or more of the materials known to show nuclear fission.”1785 Serber said one kilogram of U235 was approximately equal to 20,000 tons of TNT and noted that nature had almost located that conversion beyond human meddling: “Since only the last few generations [of the chain reaction] will release enough energy to produce much expansion [of the critical mass], it is just possible for the reaction to occur to an interesting extent before it is stopped by the spreading of the active material.”1786 If fission had proceeded more energetically the bombs would have slept forever in the dark beds of their ores.
Serber discussed fission cross sections, the energy spectrum of secondary neutrons, the average number of secondary neutrons per fission (measured by then to be about 2.2), the neutron capture process in U238 that led to plutonium and why ordinary uranium is safe (it would have to be enriched to at least 7 percent U235, the young theoretician pointed out, “to make an explosive reaction possible”).1787, 1788 He was already calling the bomb “the gadget,” its nickname thereafter on the Hill, a bravado metonymy that Oppenheimer probably coined.1789 The calculations Serber reported indicated a critical mass for metallic U235 tamped with a thick shell of ordinary uranium of 15 kilograms: 33 pounds. For plutonium similarly tamped the critical mass might be 5 kilograms: 11 pounds. The heart of their atomic bomb would then be a cantaloupe of U235 or an orange of Pu239 surrounded by a watermelon of ordinary uranium tamper, the combined diameter of the two nested spheres about 18 inches. Shaped of such heavy metal the tamper would weigh about a ton. The critical masses would eventually have to be determined by actual test, Serber said.
He went on to speak of damage. Out to a radius of a thousand yards around the point of explosion the area would be drenched with neutrons, enough to produce “severe pathological effects.”1790 That would render the area uninhabitable for a time. It was clear by now—it had not been clear before—that a nuclear explosion would be no less damaging than an equivalent chemical explosion. “Since the one factor that determines the damage is the energy release, our aim is simply to get as much energy from the explosion as we can. And since the materials we use are very precious, we are constrained to do this with as high an efficiency as is possible.”1791
Efficiency appeared to be a serious problem. “The reaction will not go to completion in an actual gadget.”1792 Untamped, a bomb core even as large as twice the critical mass would completely fission less than 1 percent of its nuclear material before it expanded enough to stop the chain reaction from proceeding. An equally disadvantageous secondary effect also tended to stop the reaction: “as the pressure builds up it begins to blow off material at the outer edge of the [core].”1793 Tamper always increased efficiency; it reflected neutrons back into the core and its inertia—not its tensile strength, which was inconsequential at the pressures a chain reaction would generate—slowed the core’s expansion and helped keep the core surface from blowing away. But even with a good tamper they would need more than one critical mass per bomb for reasonable efficiency.
Detonation was equally a problem. To detonate their bombs they would have to rearrange the core material so that its effective neutron number, which corresponded to Fermi’s k, changed from less than 1 to more than 1. But however they rearranged the material—firing one subcritical piece into another subcritical piece inside the barrel of a cannon seemed to be the simplest option—they would have no slow, smooth transition as Fermi had with CP-1. If they fired one piece into another at the high velocity of 3,000 feet per second it would take the pieces about a thousandth of a second to assemble themselves. But since more than one critical mass was necessary for an efficient explosion the pieces would be supercritical before they had completely mated. If a stray neutron then started a chain reaction, the resulting inefficient explosion would proceed from beginning to end in a few millionths of a second. “An explosion started by a premature neutron will be all finished before there is time for the pieces to move an appreciable distance.”1794Which meant that the neutron background—spontaneous-fission neutrons from the tamper, neutrons knocked from light-element impurities, neutrons from cosmic rays—would have to be kept as low as possible and the rearrangement of the core material managed as fast as possible. On the other hand, they did not have to worry that a fizzle would drop an intact bomb into enemy hands; even a fizzle would release energy equivalent to at least sixty tons of TNT.
Predetonation would reduce the bomb’s efficiency, Serber repeated; so also might postdetonation. “When the pieces reach their best position we want to be very sure that a neutron starts the reaction before the pieces have a chance to separate and break.”1795 So there might be a third basic component to their atomic bomb besides nuclear core and confining tamper: an initiator—a Ra + Be source or, better, a Po + Be source, with the radium or polonium attached perhaps to one piece of the core and the beryllium to the other, to smash together and spray neutrons when the parts mated to start the chain reaction.
Firing the pieces of core together, the Berkeley theoretician continued, “is the part of the job about which we know least at present.”1796 The summer-study group had examined several ingenious designs. The most favorable fired a cylindrical male plug of core and tamper into a mated female sphere of tamper and core, illustrated here in cross section from the Los Alamos Primer:
The target sphere could be simply welded to the muzzle of a cannon; then the cylinder, which might weigh about a hundred pounds, could be fired up the barrel like a shell:
The highest muzzle velocity available in U.S. Army guns is one whose bore is 4.7 inches and whose barrel is 21 feet long. This gives a 50 lb. projectile a muzzle velocity of 3150 ft/sec. The gun weighs 5 tons. It appears that the ratio of projectile mass to gun mass is about constant for different guns so a 100 lb. projectile would require a gun weighing about 10 tons.1798
For a mechanism eight times lighter or with double the effective muzzle velocity they could weld two guns together at their muzzles and fire two projectiles into each other. Synchronization would be a problem with such a design and efficiency might require four critical masses instead of two, a demand which would significantly delay delivering a usable bomb.
Serber also described more speculative arrangements: sliced ellipsoidal core-tamper assemblies like halves of hard-boiled eggs that slid together; wedge-shaped quarters of core/tamper like sections of a quartered apple mounted on a ring. That was an odd and striking design, sketched in the mimeographed Primer as probably on a blackboard before, and it did not go unnoticed. “If explosive material were distributed around the ring and fired the pieces would be blown inward to form a sphere”:1799
Autocatalytic bombs—bombs in which the chain reaction itself, as it proceeded, increased the neutron number for a time—looked less promising. The cleverest notion incorporated “bubbles” of boron-coated paraffin into the U235 core; as the core expanded it would compress the neutron-absorbing boron and render it less efficient, freeing more neutrons for fission chains. But: “All autocatalytic schemes that have been thought of so far require large amounts of active material, are low in efficiency unless very large amounts are used, and are dangerous to handle. Some bright ideas are needed.”1801
Their immediate work of experiment, Serber concluded, would be measuring the neutron properties of various materials and mastering the ordnance problem—the problem, that is, of assembling a critical mass and firing the bomb. They would also have to devise a way to measure a critical mass for fast fission with subcritical amounts of U235 and Pu239. They had a deadline: workable bombs ready when enough uranium and plutonium was ready. That probably gave them two years.
The Japanese physics colloquium in Tokyo had decided in March 1943 that an atomic bomb was possible but not practically attainable by any of the belligerents in time to be of use in the present war. Robert Serber’s lectures at Los Alamos in early April asserted to the contrary that for the United States an atomic bomb was both possible and probably attainable within two years. The Japanese assessment was essentially technological. Like Bohr’s assessment in 1939, it overestimated the difficulty of isotope separation and underestimated U.S. industrial capacity. It also, as the Japanese government had before Pearl Harbor, underestimated American dedication. Collective dedication was a pattern of Japanese culture more than of American. But Americans could summon it when challenged, and couple it with resources of talent and capital unmatched anywhere else in the world.
The Europeans at Los Alamos complained of the barbed wire. With the exception, apparently, only of Edward Condon, who found security so oppressive he quit the project within weeks of his arrival and went back to Westinghouse, the Americans accepted the fences around their work and their lives as a necessity of war. The war was a manifestation of nationalism, not of science, and such did their duty on the Hill appear at first to be. There was “relatively little nuclear physics” at Los Alamos, Bethe says, mostly cross-section calculations.1802 They thought they were assembled to engineer a “practical military weapon.” That was first of all a national goal. Science—a fragile, nascent political system of limited but increasing franchise—would have to wait until the war was won. Or so it seemed. But a few among the men and women gathered at Los Alamos—certainly Robert Oppenheimer—sniffed a paradox. They proposed in fact to win the war with an application of their science. They dreamed further that by that same application they might forestall the next war, might even end war as a means of settling differences between nations. Which must in the long run have decisive consequences, one way or the other, for nationalism.
* * *
By the time Robert Serber finished his orientation lectures at Los Alamos in mid-April most of the scientific and technical staff was on hand, many lodged temporarily in the surviving buildings of the Ranch School. Now began a second phase of the conference, to plan the laboratory’s work. “If there were any ground-breaking ceremonies at Los Alamos like champagne or cutting ribbons,” John Manley comments, “I was unaware of them.1803 Most of us who were there felt that the conference in April, 1943, was really the ground-breaking ceremony.”1804 Rabi, Fermi and Samuel Allison arrived from Cambridge and Chicago to serve as senior consultants. Groves appointed a review committee—W. K. Lewis again, an engineer named E. L. Rose who was thoroughly experienced in ordnance design, Van Vleck, Tolman and one other expert—to follow planning and advise. Groves despite his formidable competence as an organizer and administrator was intellectually insecure around so many distinguished scientists, as who would not be?
They laid their plans, often during hikes into the uninhabited wild surroundings of the mesa. They had to rely heavily on theoretical anticipations of the effects they wanted to study; that was their basic constraint. Any experimental device that demonstrated a fast-neutron chain reaction to completion would use up at least one critical mass: there could be no controlled, laboratory-scale bomb tests, no squash-court demonstrations. They decided they had to analyze the explosion theoretically and work out ways to calculate the stages of its development. They needed to understand how neutrons would diffuse through the core and the tamper. They needed a theory of the explosion’s hydrodynamics—the complex dynamic motions of its fluids, which the core and tamper would almost instantly become as their metals heated from solid to liquid to gas.
They needed detailed experiments to observe bomb-related nuclear phenomena and they needed integral experiments to duplicate as much as possible the full-scale operation of the bomb. They had to develop an initiator to start the chain reaction. They had to devise technology for reducing uranium and plutonium to metal, for casting and shaping that metal, possibly for alloying it to improve its properties. Particularly with plutonium, they had to discover and measure those properties in the first place and do so quickly when more than microgram quantities began to arrive. As a sideline, because they agreed that work on the Super should continue at second priority, they wanted to construct and operate a plant for liquefying deuterium at −429°F—the cryogenics plant to be built near the south rim of the mesa.
Ordnance work was crucial. From the April discussions came immediate breakthroughs. An Oppenheimer recruit from the National Bureau of Standards who had been a protégé at Caltech, a tall, thin, thirty-six-year-old experimental physicist named Seth Neddermeyer, imagined an entirely different strategy of assembly.1805 Neddermeyer could not quite remember after the war the complex integrations by which he came to it. An ordnance expert had been lecturing. The expert had quibbled at the physicists’ use of the word “explosion” to describe firing the bomb parts together. The proper word, the expert said, was “implosion.” During Serber’s lectures Neddermeyer had already been thinking about what must happen when a heavy cylinder of metal is fired into a blind hole in an even heavier metal sphere. Spheres and shock waves made him think about spherically symmetrical shock waves, whatever those might be. “I remember thinking of trying to push in a shell of material against a plastic flow,” Neddermeyer told an interviewer later, “and I calculated the minimum pressures that would have to be applied. Then I happened to recall a crazy thing somebody had published about firing bullets against each other. It may have had a photograph of two bullets liquefied on impact. That is what I was thinking when the ballistics man mentioned implosion.”1806
Two bullets fired against each other recall the double-gun model of the Los Alamos Primer. There were other clues to Neddermeyer’s new strategy placed evocatively in the Primer as well. That document notes that when the surface of the bomb core blows off, it “expands into the tamper material, starting a shock wave which compresses the tamper material sixteenfold.”1807 The Primer emphasizes more than once that the expansion of the core would be the greatest obstacle to an efficient explosion. It may have occurred to Neddermeyer that if a tamper merely by its inertia—by its tendency to stay where it is when the swelling core begins to push out against it—could resist the core’s expansion and thereby increase the efficiency of the explosion, a tamper that somehow pushed backagainst the core might do even better. The compressing of the boron bubbles in the autocatalytic bomb may also have been suggestive. Finally, the Primer offered the interesting model of four apple-quarter wedges of core/tamper fired together by an encompassing explosive ring. “At this point,” says Neddermeyer, “I raised my hand.”1808
He proposed packing a spherical layer of high explosives around a spherical assembly of tamper and a hollow but thick-walled spherical core. Detonated at many points simultaneously, the HE would blow inward. The shock wave from that explosion would squeeze the tamper from all sides, which in turn would squeeze the core. Squeezing the core would change its geometry from hollow shell to solid ball. What had been subcritical because of its geometry would be squeezed critical far faster and more efficiently than any mere gun could fire. “The gun will compress in one dimension,” Manley remembers Neddermeyer telling them. “Two dimensions would be better. Three dimensions would be better still.”1809
A three-dimensional squeeze inward was implosion. Neddermeyer had just defined a possible new way to fire an atomic bomb. The idea had been suggested previously, but no one had carried it beyond conversation. “At a meeting on ordnance problems late in April,” records the Los Alamos technical history, “Neddermeyer presented the first serious theoretical analysis of the implosion. His arguments showed that the compression of a . . . sphere by detonation of a surrounding high-explosive layer was feasible, and that it would be superior to the gun method both in its high velocity and shorter path of assembly.”1810
The response at the time was not encouraging. “Neddermeyer faced stiff opposition from Oppenheimer and, I think, Fermi and Bethe,” Manley says.1811 How do you make a shock wave spherically symmetrical? How do you keep tamper and core from squirting out in every direction as water does when squeezed between cupped hands? “Nobody . . . really took [implosion] very seriously,” Manley adds.1812 But Oppenheimer had been wrong before—even about the possibility of fission when Luis Alvarez dropped by to report it in 1939, wrong for the fifteen minutes it took him to think past the stubbornness with which he rejected any possibility he had not himself foreseen. Apparently he was learning to steer by that grudging incredulity as Bohr steered by the madness of a truly original idea. “This will have to be looked into,” he told Neddermeyer in private conference after the dismissive public debate.1813 He took his revenge for the trouble Neddermeyer was causing him by appointing that thoroughgoing loner to the newly invented post of group leader in the Ordnance Division for implosion experimentation.
The other fresh insight remembered from the April conference corrected an error that everyone wondered afterward how anyone could have overlooked. The error is perhaps a measure of how unfamiliar the physicists were with ordnance. E. L. Rose, the research engineer on Groves’ review committee, woke up one day to realize that the Army cannon the physicists were basing their estimates on weighed five tons only because it had to be sturdy enough for repeated firing. A gun that wore an atomic bomb welded to its muzzle could be flimsier: it would be fired only once, after which it would vaporize and drift away. That specification cut its weight drastically and promised a practical, flyable bomb.
Fermi, superb experimentalist that he was, contributed valuably to the program of experimental studies, defining with clarity problems that needed to be examined. For him the war work was duty, however, and the eager conviction he found on the Hill puzzled him. “After he had sat in on one of his first conferences here,” Oppenheimer recalls, “he turned to me and said, ‘I believe your people actually want to make a bomb.’ I remember his voice sounded surprised.”1814
The leaders attended a party one night that April at Oppenheimer’s house, the log-and-stucco former residence of the Ranch School headmaster. Edward Condon, whose father had been a builder of railroads in the West, who had worked as a newspaper reporter in tough Oakland, found occasion at Oppenheimer’s party to satirize Los Alamos’ Panglossian mood.1815 He was an exceptional theoretician; he and Oppenheimer had boarded together at Göttingen; Condon thought they were fast friends. He would soon clash bitterly with Groves over compartmentalization and find that his friend the director had higher priorities than backing him up. Now, sitting in a corner at the director’s house, Condon pulled from a bookshelf a copy of Shakespeare’s The Tempest and skimmed it for speeches meant for Prospero’s enchanted island that might play contrapuntally against Oppenheimer’s high and dry and secret mesa where no one had a street address, where mail was censored, where drivers’ licenses went nameless, where children would be born and families live and a few people die behind a post-office box in devotion to the cause of harnessing an obscure force of nature to build a bomb that might end a brutal war. There are many speeches in The Tempest that would have fit the occasion but one certainly that Condon would not have missed reading aloud to the assembled, Miranda’s speech that Aldous Huxley borrowed for an ironic title:
O, wonder!
How many goodly creatures are there here!
How beauteous mankind is! O brave new world
That has such people in’t!
The British had chosen not to bomb Vemork because Lief Tronstad, the physical chemist attached to Norwegian intelligence in London, had warned that hitting the hydrochemical facility’s liquid-ammonia storage tanks would almost certainly kill large numbers of Norwegian workers. But the British had in any case long since abandoned precision bombing.
Winston Churchill had declared himself strongly in favor of strategic air attack early in the war, speaking even of extermination. In July 1940, in the desperate time after the debacle of Dunkirk and at the beginning of the Battle of Britain, Churchill had written his Minister of Aircraft Production to that effect: “But when I look round to see how we can win the war I see that there is only one sure path . . . and that is absolutely devastating, exterminating attack by very heavy bombers from this country upon the Nazi homeland. We must be able to overwhelm them by this means, without which I do not see a way through.”1816, 1817
The slide from precision bombing attacks on industry to general attacks on cities followed less from political decisions than from inadequate technology. Bomber Command had attempted long-distance daylight precision bombing early in the war but had been unable to defend its aircraft against German fighters and flak so far from home. It therefore switched to night bombing, which reduced losses but severely impaired accuracy. If it was logical to bomb factories and other strategic targets to reduce the enemy’s ability to wage war, it began to seem equally logical to bomb the blocks of workers’ housing that surrounded those targets; the workers, after all, made the factories run. Sir Arthur Harris, who became chief of Bomber Command in early 1942, notes in his war memoirs of this transitional period in the summer of 1941 that “the targets chosen were in congested industrial areas and were carefully picked so that bombs which overshot or undershot the actual railway centers under attack [in this instance] should fall on these areas, thereby affecting morale. This programme amounted to a halfway stage between area and precision bombing.”1818 “Morale” is here and elsewhere in the literature of air power a euphemism for the bombing of civilians. Another sign of halfway status at this stage was permission to dump bombs before exiting Germany if crews had missed their targets.
Churchill says he authorized a study of bombing accuracy at Frederick Lindemann’s suggestion which discovered in the summer of 1941 “that although Bomber Command believed they had found the target, two-thirds of crews actually failed to strike within five miles of it. . . . Unless we could improve on this there did not seem much use in continued night bombing.”1819 In November the government ordered its bomber arm to reduce operations over Germany.
To reduce strategic bombing operations was to admit failure in both theory and practice, and it was to do so at a time when the USSR was fully engaged with the German armies on the Eastern Front and Joseph Stalin was demanding the Allies open a second front in the West. Neither Britain nor the United States was nearly prepared yet to invade Europe on the ground, but both nations might offer such aid as air attack could bring. Aiding the Soviet Union was a political justification for continuing some kind of strategic bombing campaign, though it hardly placated Stalin. Headlines proclaiming almost daily bombing raids also helped keep the home front happy when the ground war stalled.1820
Yet Allied politics and domestic propaganda could not have been the primary reasons for the drift from precision to area bombing, because U.S. air forces beginning to arrive in Britain in 1942 planned and carried out precision daylight bombing, though not often effectively, until much later in the war. Rather, Bomber Command switched programs in order to justify its continued existence as a service with a mission separate from Army and Navy tactical support, cutting theory to fit the facts. It found an ally in the newly ennobled Lindemann, Lord Cherwell, who calculated in March 1942 that bombing might destroy the housing of a third of the German population within a year if sufficiently pursued against industrial urban areas. Patrick Blackett and Henry Tizard thought Cherwell’s estimate far too optimistic and dissented vigorously, but Cherwell had the Prime Minister’s ear.
Sir Arthur Harris—“Butch,” his staff came to call him, short for “the Butcher”—took over Bomber Command in February and promulgated a new approach to the air war: “It has been decided that the primary objective of your operations should now be focussed on the morale of the enemy civil population and in particular, of the industrial workers.”1821 Harris had witnessed the London Blitz; it convinced him, he writes, that “a bomber offensive of adequate weight and the right kind of bombs would, if continued for long enough, be something that no country in the world could endure.”1822 His argument was valid, of course, though what “the right kind of bombs” might be would require the work of the Manhattan Project to reveal. Hitler’s terror bombing taught Britain not terror but forceful imitation. Harris certainly despised the Germans for starting and perpetuating two world wars. But he seems to have thought less about killing civilians than about solving the problem of making Bomber Command a measurably effective force. If night bombing and area bombing were the only tactics that paid a reasonable return in destruction at a reasonable price in lost aircraft and aircrew lives, then he would dedicate Bomber Command to perfecting those tactics and measure success not in factories rendered inoperative but in acres of cities flattened. Which is to say, area bombing was invented to give bombers targets they could hit.
An incendiary attack on the old Baltic port of Lübeck in March burned much of the town and produced four-figure casualties for the first time in the bombing campaign. On May 20, to demonstrate Bomber Command’s effectiveness at a time of public debate, Harris mustered every aircraft he could find—hundreds of two-engine bombers of light payload and even training planes—to launch a thousand-bomber raid on Cologne. For that successful assault he organized what came to be called a bomber “stream,” the aircraft flying in massed continuous formations to overwhelm defenses rather than in small and vulnerable packets as before, and destroyed some eight square miles of the ancient city on the Rhine with 1,400 tons of bombs, two-thirds of them incendiary. Finally, in August, encouraged by Cherwell, Bomber Command deployed a Pathfinder force: skilled advance crews that marked targets with colored flares so that less experienced pilots following in the lethal stream could more easily find their aiming points.
No fleet of bombers could yet accurately deliver enough high explosives to raze a city. The Lübeck bombing had been planned to test the theory that area bombing worked best by starting fires. If the bombloads were incendiary, then the massed aircraft might combine their destructiveness, wind and weather cooperating, rather than disperse it on isolated targets. The theory worked at Lübeck and again at Cologne and because it worked it won adoption. At the end of 1942 the British Chiefs of Staff called for “the progressive destruction and dislocation of the enemy’s war industrial and economic system, and the undermining of his morale to a point where his capacity for armed resistance is fatally weakened.” Churchill and Roosevelt affirmed the British plan for an aerial war of attrition in a directive issued at the conclusion of the Casablanca Conference in late January 1943.
On May 27, 1943, as work began at Los Alamos following the April conferences, Bomber Command ordered Hamburg attacked. Its Most Secret Operation Order No. 173 stated its new policy of mass destruction explicitly:
INFORMATION1823
The importance of HAMBURG, the second largest city in Germany with a population of one and a half millions, is well known . . . . The total destruction of this city would achieve immeasurable results in reducing the industrial capacity of the enemy’s war machine. This, together with the effect on German morale, which would be felt throughout the country, would play a very important part in shortening and in winning the war.
2. The “Battle of Hamburg” cannot be won in a single night. It is estimated that at least 10,000 tons of bombs will have to be dropped to complete the process of elimination . . . . This city should be subjected to sustained attack . . . .
3. . . . It is hoped that the night attacks will be preceded and/or followed by heavy daylight attacks by the United States VIIIth Bomber Command.
INTENTION
4. To destroy HAMBURG.
The operation was code-named Gomorrah. Notice the significant claim that it would help shorten and win the war.
Operation Gomorrah began on the night of July 24, 1943, a hot summer Saturday in Hamburg under clear skies.1824 Pathfinder bombers used radar to aid marking, and the initial Hamburg aiming point was chosen not for its strategic significance but for its distinctive radar reflection: a triangle of land at the junction of the Alster and North Elbe rivers, near the oldest part of the city and far from any war industry. Bomber Command had learned to adjust targeting for creep-back, the tendency of bombardiers to release their bombs as quickly as possible upon approaching the flak-infested aiming point that led to a gradual backup of impacts. From the ground the bombs seemed to unroll in the direction of the bomber stream’s approach; survivors named the phenomenon “carpet bombing.” Targeters incorporated creep-back into their calculations by setting the aiming point several miles forward of the intended target area. The creep-back districts behind the Hamburg aiming point to a distance of four miles were entirely residential.
To give the bombers further advantage Churchill had authorized the first use of the secret radar-jamming device known as Window: bales of 10.5-inch strips of aluminum foil to be pushed out of the bombers en route to the target to disperse on the wind and cloud German defensive radar. Window worked so well that of the 791 planes of the initial raid only twelve were lost.
Hamburg sustained heavy damage that first night but not damage even on the scale of Cologne; 1,300 tons of high explosives and almost 1,000 tons of incendiaries killed about 1,500 people and left many thousands homeless. More important for what would follow, the first raid seriously disrupted communications and overwhelmed firefighting forces.
Daylight precision bombing by American B-17’s followed on July 25 and 26, attacks meant for a submarine yard and an aircraft engine factory. Smoke from the British bombing and from German defensive generators obscured the targets and they were only lightly damaged.
Harris ordered a maximum bombing effort against Hamburg again for the night of July 27. Targeters fixed the same aiming point but aligned the bomber stream to approach from the northeast rather than the north to set its creep-back over districts dense with workers’ apartment buildings. Since the mix of 787 bombers for this second raid would include more Halifaxes and Stirlings, and they could carry less weight of weapons and fuel than the longer-distance Lancasters, the mix of bombs was also changed, high explosives reduced and incendiaries increased to more than 1,200 tons. More experienced pilots also came aboard, higher-ranking officers signing on to observe the effects of Window. These accidents of arrangement contributed their share to the night’s catastrophe.
At 6 P.M. in Hamburg on July 27 the temperature was 86 degrees and the humidity 30 percent. Fires still burned in stores of coal and coke in the western sector of the city. Since the fires would render a blackout ineffective most of Hamburg’s firefighting equipment had been moved to the area to douse them. “It was completely quiet,” recalls a German woman who lived in a district targeted for creep-back, miles to the northeast. “ . . . It was an enchantingly beautiful summer night.”1825
Pathfinders started dropping yellow markers and bombs at fifty-five minutes past midnight on July 28. Five minutes later the main bomber stream arrived. Marking was good and creep-back was slow. Later arrivals began to notice a difference between this raid and others they had flown: “Most of the raids we did looked like gigantic firework displays over the target area,” a flight sergeant remarks, “but this was ‘the daddy of them all.’ ”1826 A flight lieutenant distinguishes the difference:
The burning of Hamburg that night was remarkable in that I saw not many fires but one. Set in the darkness was a turbulent dome of bright red fire, lighted and ignited like the glowing heart of a vast brazier. I saw no flames, no outlines of buildings, only brighter fires which flared like yellow torches against a background of bright red ash. Above the city was a misty red haze. I looked down, fascinated but aghast, satisfied yet horrified. I had never seen a fire like that before and was never to see its like again.1827
The summer heat and low humidity, the mix of high-explosive and incendiary bombs that made kindling and then ignited it and the absence of firefighting equipment in the bombed districts conspired to assemble a new horror. An hour after the bombing began the horror had a name, recorded first in the main log of the Hamburg Fire Department: Feuersturm: firestorm. A Hamburg factory worker remembers its beginning, some twenty minutes into the one-hour bombing raid:
Then a storm started, a shrill howling in the street. It grew into a hurricane so that we had to abandon all hope of fighting the [factory] fire. It was as though we were doing no more than throwing a drop of water on to a hot stone. The whole yard, the canal, in fact as far as we could see, was just a whole, great, massive sea of fire.1828
Small fires had coalesced into larger fires and, greedy for oxygen, had sucked air from around the coalescing inferno and fanned further fires there. That created the wind, a thermal column above the city like an invisible chimney above a hearth; the wind heated the fury at the center of the firestorm to more than 1,400 degrees, heat sufficient to melt the windows of a streetcar, wind sufficient to uproot trees. A fifteen-year-old Hamburg girl recalls:
Mother wrapped me in wet sheets, kissed me, and said, “Run!” I hesitated at the door. In front of me I could see only fire—everything red, like the door to a furnace. An intense heat struck me. A burning beam fell in front of my feet. I shied back but, then, when I was ready to jump over it, it was whirled away by a ghostly hand. I ran out to the street. The sheets around me acted as sails and I had the feeling that I was being carried away by the storm. I reached . . . a five-storey building in front of which we had arranged to meet again. . . . Someone came out, grabbed me by the arm, and pulled me into the doorway.1829
The fire filled the air with burning embers and melted the streets, a nineteen-year-old milliner reports:
We came to the door which was burning just like a ring in a circus through which a lion has to jump. . . . The rain of large sparks, blowing down the street, were each as large as a five-mark piece. I struggled to run against the wind in the middle of the street but could only reach a house on the corner . . . .1830
We got to the Löschplatz [park] all right but I couldn’t go on across the Eiffestrasse because the asphalt had melted. There were people on the roadway, some already dead, some still lying alive but stuck in the asphalt. They must have rushed on to the roadway without thinking. Their feet had got stuck and then they had put out their hands to try to get out again. They were on their hands and knees screaming.
The firestorm completely burned out some eight square miles of the city, an area about half as large as Manhattan. The bodies of the dead cooked in pools of their own melted fat in sealed shelters like kilns or shriveled to small blackened bundles that littered the streets. Or worse, as the woman who was once the fifteen-year-old girl horribly recreates:
Four-storey-high blocks of flats [the next day] were like glowing mounds of stone right down to the basement. Everything seemed to have melted and pressed the bodies away in front of it. Women and children were so charred as to be unrecognizable; those that had died through lack of oxygen were half-charred and recognizable. Their brains had tumbled from their burst temples and their insides from the soft parts under the ribs. How terribly these people must have died. The smallest children lay like fried eels on the pavement.1831
Bomber Command killed at least 45,000 Germans that night, the majority of them old people, women and children.
The bombing of Hamburg was hardly unique. It was one atrocity in a war of increasing atrocities. Between 1941 and 1943 the German Army on the Eastern Front captured and enclosed in prisoner-of-war camps without food or shelter some two million Soviet soldiers; at least one million of them died of exposure and starvation.1832 During the same period the Final Solution to the Jewish Question—the vast Nazi program to exterminate the European Jews—began in deadly earnest after the Wannsee Conference of coordinating agencies met in suburban Berlin on January 20, 1942. Whatever moral issues such atrocities raise, they resulted from the progressive escalation of the war by all its belligerents in pursuit of victory. (Even the Final Solution: because the Nazis believed the Jews constituted a separate nation lodged subversively in their midst—nationality being defined in the Nazi canon primarily in terms of race—and as such the nation with which the Third Reich was preeminently at war. It was Hitler’s particular perversity to define victory over the Jews as extermination; the Allies in their defensive war against Germany and Japan wanted only total surrender, in return for which the mass killing of combatants and civilians would stop.)
One way the belligerents could escalate was to improve their death technologies. Better bombers and better bomber defenses such as Window were hardware improvements; so were the showers at the death camps efficiently pumped with the deadly fumigant Zyklon B. The bomber-stream system and allowance for creep-back were software improvements; so were the schedules Adolf Eichmann devised that kept the trains running efficiently to the camps.
The other way the belligerents could escalate was to enlarge the range of permissible victims their death technologies might destroy. Civilians had the misfortune to be the only victims left available. Better hardware and software began to make them also accessible in increasing numbers. No great philosophical effort was required to discover acceptable rationales. War begot psychic numbing in combatants and civilians alike; psychic numbing prepared the way for increasing escalation.
Extend war by attrition to include civilians behind the lines and war becomes total. With improving technology so could death-making be. The bombing of Hamburg marked a significant step in the evolution of death technology itself, massed bombers deliberately churning conflagration. It was still too much a matter of luck, an elusive combination of weather and organization and hardware. It was still also expensive in crews and matériel. It was not yet perfect, as no technology can ever be, and therefore seemed to want perfecting.
The British and the Americans would be enraged to learn of Japanese brutality and Nazi torture, of the Bataan Death March and the fathomless horror of the death camps. By a reflex so mindlessly unimaginative it may be merely mammalian, the bombing of distant cities, out of sight and sound and smell, was generally approved, although neither the United States nor Great Britain admitted publicly that it deliberately bombed civilians.1833 In Churchill’s phrase, the enemy was to be “de-housed.” The Jap and the Nazi in any case had started the war. “We must face the fact that modern warfare as conducted in the Nazi manner is a dirty business,” Franklin Roosevelt told his countrymen. “We don’t like it—we didn’t want to get in it—but we are in it and we’re going to fight it with everything we’ve got.”1834
* * *
The Los Alamos review committee headed by W.K. Lewis of MIT reported its findings on May 10, 1943. It approved the laboratory’s nuclear physics research program. It recommended that theoretical investigation of the thermonuclear bomb continue at second priority, subordinate to fission bomb work. It proposed a major change in the chemistry program: final purification of plutonium on the Hill, because Los Alamos would be ultimately responsible for the performance of the plutonium bomb and because the scarce new element would be used and reused for experiments during the months before a sufficient quantity accumulated to load a bomb and would have to be frequently repurified. The Lewis committee also concurred in a recommendation Robert Oppenheimer had made in March that ordnance development and engineering should begin immediately at Los Alamos rather than wait until nuclear physics studies were complete. General Groves accepted the committee’s findings; they dictated an immediate doubling of Hill personnel.1835 Thereafter until the end of the war the Los Alamos working population would double every nine months. The dust of construction never settled; housing would always be short, water scarce, electricity intermittent. Groves spent not a penny more than necessary on comforts for civilians.
The bottom pole piece of the Harvard cyclotron had been laid on April 14; by the first week in June Robert Wilson’s cyclotron group saw signs of a beam. The Wisconsin long-tank Van de Graaff came on line at 4 million volts on May 15 and the 2 MV short-tank Van de Graaff on June 10. In July the first physics experiment completed at Los Alamos counted the number of secondary neutrons Pu239 emitted when it fissioned. “In this experiment,” says the Los Alamos technical history, “the neutron number was measured from an almost invisible speck of plutonium and found to be somewhat greater even than for U235.”1836 The experiment thus established what had not yet been confirmed despite the expensive rush of building: that plutonium emitted sufficient secondary neutrons to chain-react.
The speck of plutonium was Glenn Seaborg’s 200-milligram sample of Met Lab oxide, which he had sent to Los Alamos at the beginning of the month. Seaborg had worked himself sick at the Met Lab that spring—an upper respiratory infection compounded with exhaustion and a persistent fever—and came to New Mexico with his wife during July to vacation. (“I guess I deliberately chose to be near the plutonium,” he muses. “I wonder why?”) Too much peace and quiet at a guest ranch threatened to exhaust him further and on July 21 he and his wife moved to the adobe-style La Fonda Hotel in Santa Fe.1837 Compartmentalization put Los Alamos off limits. The Seaborgs were ready to return to Chicago on Friday, July 30, and Seaborg proposed to carry the Pu sample, most of the world’s supply, back with him on the train. Robert Wilson and another physicist made the transfer before dawn in the restaurant where the Seaborgs were having breakfast in Santa Fe, Wilson arriving in a pickup armed Western-style with his personal Winchester .32 deer-hunting rifle to guard a highly valuable but barely visible treasure. “Then I just put it in my pocket and then into my suitcase,” Seaborg remembers.1838 He proceeded to Chicago unarmed.
To direct the expanded Ordnance Division Groves asked the Military Policy Committee in Washington to recommend a good man, preferably a military officer. Vannevar Bush knew a naval officer—would Groves mind? “Of course not,” the general humphed.1839 Bush proposed Captain William S. “Deke” Parsons, a 1922 Annapolis graduate then responsible under Bush for field-testing the proximity fuse.1
Parsons had also worked on early radar development and served as gunnery officer on a destroyer and experimental officer at the Naval Proving Ground in Dahlgren, Virginia. He was forty-three, cool, vigorous, trim, nearly bald, spit-and-polish but innovative; “all his life,” one of the men who worked for him at Los Alamos testifies in praise, “he fought the silly regulations and the conservatism of the Navy.”1840 Groves liked him; “within a few minutes [of meeting him],” the general says, “I was sure he was the man for the job.”1841 Oppenheimer interviewed the man for the job in Washington and agreed. Parsons was married to Martha Cluverius, a Vassar graduate and the daughter of an admiral; with two blond daughters and a cocker spaniel the couple arrived at Los Alamos in an open red convertible in June.
Parsons’ first order of business was the plutonium gun. Because it needed a muzzle velocity of at least 3,000 feet per second it would have to be 17 feet long. It should weigh no more than a ton, a fifth of the usual weight of a gun that size, which meant it would have to be machined from strong high-alloy steel. It would not require rifling but needed three independently operated primers to make sure it fired. Parsons arranged for the Navy’s gun-design section to engineer it.
Norman F. Ramsey, a tall young Columbia physicist, the son of a general, served under Parsons as group leader for delivery: for devising a way to deliver the bombs to their targets and drop them. In June he contacted the U.S. Air Force to identify a combat aircraft that could carry a 17-foot bomb. “As a result of this survey,” Ramsey writes, “it was apparent that the B-29 was the only United States aircraft in which such a bomb could be conveniently carried internally, and even this plane would require considerable modification so that the bomb could extend into both front and rear bomb bays. . . .1843, 1844 Except for the British Lancaster, all other aircraft would require such a bomb to be carried externally.” The Air Force was not about to allow a historic new weapon of war to be introduced to the world in a British aircraft, but the B-29 Superfortress was a new design still plagued with serious problems. The first service-test model had not yet flown when Ramsey began his aircraft survey in June; a flight-test model had crashed into a Seattle packing house in February and killed the plane’s entire test crew and nineteen packing-house workers.
Ramsey did not have to wait for access to a B-29 to begin collecting data on the long bomb’s ballistics, however. He mocked up a scale model and arranged to see it dropped:
On August 13, 1943, the first drop tests of a prototype atomic bomb were made at the Dahlgren Naval Proving Ground [by a Navy TBF aircraft] to determine stability in flight. These tests were on a 14/23 scale model of a bomb shape which was then thought probably suitable for a gun assembly. Essentially, the model consisted of a long length of 14-inch pipe welded into the middle of a split standard 500-pound bomb. It was officially known at Dahlgren as the “Sewer Pipe Bomb.” . . . The first test . . . was an ominous and spectacular failure. The bomb fell in a flat spin such as had rarely been seen before. However, an increase in fin area and a forward movement of the center of gravity provided stability in subsequent tests.1845
In the meantime Seth Neddermeyer, whose implosion experimentation group Parsons inherited, had visited a U.S. Bureau of Mines laboratory at Bruceton, Pennsylvania, to experiment with high explosives. Edwin McMillan, who was interested in implosion, went with the Caltech physicist:
At that point it was just Seth and myself with a few helpers. The first cylindrical implosions were done at Bruceton. You take a piece of iron pipe, wrap the explosives around it, and ignite it at several points so that you get a converging wave and squash the cylinder in. That was the birth of the experimental work on implosion, long before experimental work on the gun method.1846
Back at Los Alamos Neddermeyer set up a small research station on South Mesa, the next mesa south of the Hill across Los Alamos canyon. He fired his first tests in an arroyo on Independence Day, 1943, using iron pipe set in cans packed with TNT. Experimenting with cylinders rather than spheres simplified calculation. Because he wanted to recover the results he packed only limited amounts of explosive. “Those tests of course could not be very sophisticated,” says McMillan. “ . . . They did show that you could take metal pipes and close them right in so that they became like solid bars, indicating that this was a practical method.”1847 They also showed that the squeeze was far from uniform: the pipes emerged from the arroyo dust twisted and deformed.
When Parsons, a thoroughly pragmatic engineer, had time to look over Neddermeyer’s work he was openly contemptuous. He doubted if implosion could ever be made reliable enough for field use. Neddermeyer presented his initial results at one of the weekly colloquia Oppenheimer had instituted at Hans Bethe’s suggestion to keep everyone with a white badge—everyone cleared for secrets—informed of Tech Area progress. Richard P. Feynman, a brilliant, outspoken New York-born graduate-student theoretician from Princeton, summarized the opinion of the assembly in a phrase: “It stinks.”1848 In the name of lightheartedness Parsons was crueler. “With everyone grinding away in such dead earnest here,” he told the group, “we need a touch of relief. I question Dr. Neddermeyer’s seriousness. To my mind he is gradually working up to what I shall refer to as the Beer-Can Experiment.1849 As soon as he gets his explosives properly organized, we will see this done. The point to watch for is whether he can blow in a beer can without splattering the beer.” Implosion was even harder to do than that.
John von Neumann, the Hungarian mathematician who had come to the United States in 1930 and joined the Institute for Advanced Study, had been examining for the NDRC the complex hydrodynamics of shock waves formed by shaped charges, technology which was being applied to the American tank-killing infantry weapon known as the bazooka. Like Rabi, von Neumann had agreed to serve as an occasional Oppenheimer consultant. He visited Los Alamos at the end of the summer and looked into implosion theory, another warren of hydrodynamic complexity. Neddermeyer had devised “a simple theory that worked up to a certain level of violence in the shockwave.” Von Neumann, he says, “is generally credited with originating the science of large compressions. But I knew it before and had done it in a naive way. Von Neumann’s was more sophisticated.”1850
“Johnny was quite interested in high explosives,” Edward Teller remembers. Teller and von Neumann renewed their youthful acquaintance during the mathematician’s visit to the Hill. “In my discussions with him some crude calculations were made,” Teller continues. “The calculation is indeed simple as long as you assume that the material to be accelerated is incompressible, which is the usual assumption about solid matter. . . . In materials driven by high explosives, pressures of more than 100,000 atmospheres occur.” Von Neumann knew that, Teller says, as he did not. On the other hand:
If a shell moves in one-third of the way toward the center you obtain under the assumption of an incompressible material a pressure in excess of eight million atmospheres. This is more than the pressure in the center of the earth and it was known to me (but not to Johnny), that at these pressures, iron is not incompressible. In fact I had rough figures for the relevant compressibilities. The result of all this was that in the implosion significant compressions will occur, a point which had not been previously discussed.1851
It had been clear from the beginning that implosion, by squeezing a hollow shell of plutonium to a solid ball, could effectively “assemble” it as a critical mass much faster than the fastest gun could fire. What von Neumann and Teller now realized, and communicated to Oppenheimer in October 1943, was that implosion at more violent compressions than Neddermeyer had yet attempted should squeeze plutonium to such unearthly densities that a solid subcritical mass could serve as a bomb core, avoiding the complex problem of compressing hollow shells. Nor would predetonation threaten from light-element impurities. Develop implosion, in other words, and they could deliver a more reliable bomb more quickly.
It was possible at that point to estimate roughly the size and shape of a bomb that worked by fast implosion. The big gun bomb would be just under 2 feet in diameter and 17 feet long. An implosion bomb—a thick shell of high explosives surrounding a thick shell of tamper surrounding a plutonium core surrounding an initiator—would be just under 5 feet in diameter and a little over 9 feet long: a man-sized egg with tail fins.
Norman Ramsey started planning full-scale drop tests that autumn as the aspens brightened to yellow at Los Alamos. He offered to practice with a Lancaster. The Air Force insisted he practice with a B-29 even though the new polished-aluminum intercontinental bombers were just beginning production and still scarce. “In order that the aircraft modifications could begin,” Ramsey writes in his third-person report on this work, “Parsons and Ramsey selected two external shapes and weights as representative of the current plans at Site Y. . . .1852, 1853 For security reasons, these were called by the Air Force representatives the ‘Thin Man’ and the ‘Fat Man,’ respectively; the Air Force officers tried to make their phone conversations sound as though they were modifying a plane to carry Roosevelt (the Thin Man) and Churchill (the Fat Man). . . . Modification of the first B-29 officially began November 29, 1943.”
* * *
A captain of the Danish Army who was also a member of the Danish underground visited Niels Bohr at the House of Honor in Copenhagen early in 1943. After tea the two men retired to Bohr’s greenhouse where hidden microphones might not overhear their conversation. The British had instructed the underground that they would soon be sending Bohr a set of keys. Blind holes had been drilled in the bows of two of the keys, identical microdots implanted and the holes sealed. A captioned diagram located the holes. “Professor Bohr should gently file the keys at the point indicated until the hole appears,” the document explained. “The message can then be syringed or floated out onto a micro-slide.”1854 The captain offered to extract the microdot and have it enlarged. Bohr was no secret agent; he accepted the offer gratefully.
When the message arrived it proved to be a letter from James Chadwick. “The letter contained an invitation to my father to go to England, where he would find a very warm welcome,” Aage Bohr remembers. “ . . . Chadwick told my father that he would be able to work freely on scientific matters. But it was also mentioned that there were special problems in which his co-operation would be of considerable help.”1855 Bohr understood that Chadwick might be hinting about work on nuclear fission. The Danish physicist was still skeptical of its application. He would not stay in Denmark, he wrote Chadwick in return, “if I felt that I could be of real help . . . but I do not think that this is probable. Above all I have to the best of my judgment convinced myself that, in spite of all future prospects, any immediate use of the latest marvelous discoveries of atomic physics is impracticable.” If an atomic bomb were a serious possibility Bohr would leave. Otherwise he had compelling reasons to stay “to help resist the threat against the freedom of our institutions and to assist in the protection of the exiled scientists who have sought refuge here.”1856
The threat against Danish institutions that Bohr was helping to resist was peculiar to the German occupation of Denmark. Germany relied heavily on Danish agriculture, which supplied meat and butter rations to 3.6 million Germans in 1942 alone.1857 It was a labor-intensive agriculture of small farms and it could only continue with the cooperation of the farmers and, more broadly, of the entire Danish population. Not to arouse resistance the Nazis had allowed Denmark to keep its constitutional monarchy and continue to govern itself. The Danes in turn had extracted an extraordinary price for agreeing to cooperate under foreign occupation: the security of Danish Jews. To the Danes the eight thousand Jews in Denmark, 95 percent of them in Copenhagen, were Danish citizens first of all; their security was therefore a test of German good faith. “Danish statesmen and heads of government,” reports a historian, “one after the other, had made the security of the Jews a conditio sine qua non for the maintenance of a constitutional Danish government.”1858
But resistance, especially strikes and sabotage, gradually increased as the Danish people felt the occupation’s burden and as the tides of war began to turn against the Axis powers. The German surrender at Stalingrad on February 2, 1943, may have appeared to many Danes to be a turning point. Mussolini’s resignation and arrest the following summer on July 25 and the impending surrender of Italy certainly did. On August 28 the Nazi plenipotentiary for Denmark, Dr. Karl Rudolf Werner Best, presented the Danish government with an ultimatum at Hitler’s orders demanding that it declare a state of national emergency, forbid strikes and meetings and introduce a curfew, a ban on arms, press censorship at German hands and the death penalty for harboring arms and for sabotage. With the King’s permission the government refused. On August 29 the Nazis reoccupied Copenhagen, disarmed the Danish Army, blockaded the royal palace and confined the King.
One reason for the takeover was Nazi determination to eliminate the Danish Jews, whose exemption from the Final Solution infuriated Hitler. The Nazis had arrested several Jewish notables on August 29 (they had planned to arrest Bohr but had decided the deed would be less obvious during a general roundup). In early September Bohr learned from the Swedish ambassador in Copenhagen that his emigré colleagues, including his collaborator Stefan Rozental, were slated for arrest. He contacted the underground, which helped the emigrés escape across the Öresund to Sweden. Rozental endured nine stormy hours crowded with other refugees in a rowboat borrowed from a city park before his exhausted party made Swedish landfall.
Bohr’s turn came soon after. The Swedish ambassador took tea at the House of Honor on September 28 and hinted that Bohr would be arrested within a few days. Even professors were leaving Denmark, Margrethe Bohr remembers the diplomat emphasizing.1859The next morning word came through her brother-in-law that an anti-Nazi German woman working at Gestapo offices in Copenhagen had seen orders authorized in Berlin for the arrest and deportation of Niels and Harald Bohr.
“We had to get away the same day,” Margrethe Bohr said afterward. “And the boys would have to follow later. But many were helping. Friends arranged for a boat, and we were told we could take one small bag.”1860, 1861 In the late afternoon of September 29 the Bohrs walked through Copenhagen to a seaside suburban garden and hid in a gardener’s shed. They waited for night. At a prearranged time they left the shed and crossed to the beach. A motorboat ran them out to a fishing boat. Threading minefields and German patrols they crossed the Öresund by moonlight and landed at Linhamm, near Malmö.
Bohr had learned at the last minute that the Nazis planned to round up all the Danish Jews the next evening and deport them to Germany. Leaving his wife in southern Sweden to await the crossing of their sons he rushed to Stockholm to appeal to the Swedish government for aid. He discovered that the Swedes had offered to intern the Danish Jews but the Germans had denied that any roundup was planned.
In fact it proceeded on schedule while Bohr worked his way through the Swedish bureaucracy, but fell far short of success. The Danes, warned in advance, had spontaneously hidden their Jewish fellow citizens away. Only some 284 elderly rest-home residents had been seized.1862 The more than seven thousand Jews remaining in Denmark were temporarily safe. But few of them planned at first to leave the country; it was far from certain that Sweden would accept them and there seemed nowhere else to go.
Meeting with the Swedish Undersecretary for Foreign Affairs on September 30 Bohr had urged that Sweden make public its protest note to the German Foreign Office.1863 He saw that publicity would alert the potential victims, signal Swedish sympathy and bring pressure to bear on the Nazis to desist. The Undersecretary told him Sweden planned no further intervention beyond the confidential note. Bohr appealed to the Foreign Minister on October 2, failed to win publication of the note and determined to dispense with intermediaries. Rozental says the Danish laureate “went to see Princess Ingeborg (the sister of the Danish king Christian X) and while there expressed the desire to be received by the King of Sweden.”1864 Bohr also contacted the Danish ambassador and influential Swedish academic colleagues.1865 Rozental describes the crucial meeting with the King:
The audience . . . took place that afternoon. . . . King Gustaf said that the Swedish Government had tried a similar approach to the Germans once before, when the occupying power had started deporting Jews from Norway.1866 The . . . approach, however, had been rejected. . . . Bohr objected that in the meantime the situation had changed decisively by reason of the Allied victories, and he suggested that the offer by the Swedish government to assume responsibility for the Danish Jews should be made public. The King promised to talk to the Foreign Minister at once, but he emphasized the great difficulties of putting the plan into operation.
The difficulties were overcome. Swedish radio broadcast the Swedish protest that evening, October 2, and reported the country ready to offer asylum. The broadcast signaled a route of escape; in the next two months 7,220 Jews crossed to safety in Sweden with the active help of the Swedish coast guard. One refugee’s report of what first alerted him in hiding to the idea of escape is typical: “At the pastor’s house I heard on the Swedish radio that the Bohr brothers had fled to Sweden by boat and that the Danish Jews were being cordially received.”1867 With personal intervention on behalf of the principle of openness, which exposes crime as well as error to public view, Niels Bohr played a decisive part in the rescue of the Danish Jews.
Stockholm was alive with German agents and there was fear that Bohr would be assassinated. “The stay in Stockholm lasted only a short time,” remembers Aage Bohr. “ . . . A telegram was received from Lord Cherwell . . . with an invitation to come to England. My father immediately accepted and requested that I should be permitted to accompany him.” Aage was twenty-one at the time and a promising young physicist. “It was not possible for the rest of the family to follow; my mother and brothers stayed in Sweden.”1868
Bohr went first. The British flew their diplomatic pouch back and forth from Stockholm in an unarmed two-engine Mosquito bomber, a light, fast aircraft that could fly high enough to avoid the German anti-aircraft batteries on the west coast of Norway—flak usually topped out at 20,000 feet. The Mosquito’s bomb bay was fitted for a single passenger. On October 6 Bohr donned a flight suit and strapped on a parachute. The pilot supplied him with a flight helmet with built-in earphones for communication with the cockpit and showed him the location of his oxygen hookup. Bohr also took delivery of a stick of flares. In case of attack the pilot would dump the bomb bay and Bohr would parachute into the cold North Sea; the flares would aid his rescue if he survived.
“The Royal Air Force was not used to such great heads as Bohr’s,” says Robert Oppenheimer wryly.1869 Aage Bohr describes the near-disaster:
The Mosquito flew at a great height and it was necessary to use oxygen masks; the pilot gave word on the inter-com when the supply of oxygen should beturned on, but as the helmet with the earphones did not fit my father’s head, he did not hear the order and soon fainted because of lack of oxygen.1870 The pilot realized that something was wrong when he received no answer to his inquiries, and as soon as they had passed over Norway he came down and flew low over the North Sea. When the plane landed in Scotland, my father was conscious again.
The vigorous fifty-eight-year-old was none the worse for wear. “Once in England and recovered,” Oppenheimer continues the story, “he learned from Chadwick what had been going on.”1871 Aage arrived a week later and father and son toured Britain observing the developing activities there of the Tube Alloys project, which included a section of a pilot-scale gaseous-diffusion plant. But the center of gravity had long since shifted to the United States. The British were preparing to recover a share of the initiative by sending a mission to Los Alamos to help design the bombs; they wanted Bohr on their team to increase its influence and prestige. By then the Danish theoretician had taken what Oppenheimer calls a “good first look.” At how nuclear weapons would change the world, Oppenheimer means. He emphasizes Bohr’s developing understanding then with a potent simile: “It came to him as a revelation, very much as when he learned of Rutherford’s discovery of the nucleus [thirty] years before.”1872
So Niels Bohr prepared in the early winter of 1943 to travel to America once again with an important and original revelation in hand, this one in the realm not of physics but of the political organization of the world.
He was willing to be impressed by a mighty progress of industry. “The work on atomic energy in the USA and in England proved to have advanced much further than my father had expected,” Aage Bohr understates.1873 Robert Oppenheimer pitches his summary closer to the shock of surprise a refugee released from the suspended animation that had been occupied Denmark would have felt: “To Bohr the enterprises in the United States seemed completely fantastic.”1874
They were.