How the Bomb Was Kept From Hitler

GERMAN NATIONAL SOCIALISM AND THE QUEST FOR NUCLEAR POWER: 1939-1949 by Mark Walker. Cambridge University Press, $29.95.
HITLER WITH AN atomic bomb was the nightmare that brought the bomb into the world. Why the Germans failed to build one is the last great secret of the early history of nuclear invention. The scientific underground that linked mainly Jewish émigrés with old friends and colleagues still in Germany passed along a continuing stream of troubling news as war came on in 1939: Nazi officials held a secret meeting to discuss fission in April; the military took an interest as soon as war broke out in September; a research program was soon established at the Kaiser Wilhelm Institut für Physik, under the brilliant young physicist Carl Friedrich von Weizsäcker, the intimate friend and protégé of Werner Heisenberg, one of the two or three greatest physicists of the century. By mid-1940, after the fall of France, Germany seemed to have everything it needed for a major effort to invent atomic bombs—access to uranium ore and heavy water, the attention of high Nazi officials and the military, and above all, scientists of the first rank.
None of the great German physicists was feared more than Heisenberg, the winner of a Nobel Prize in 1932 for his work in quantum mechanics, world famous as the author of the “uncertainty principle.”He was young, not yet forty when the war began, intellectually proud, a bit stiff in manner with those he didn’t know. Germans called it “correct,” the quality of doing without fail or hesitation what is right, in the sense of proper and expected. German science had behaved “correctly” when Hitler purged the universities of Jews, beginning in April of 1933—that is, with few exceptions, acquiesced by standing aloof. During a visit to the United States in the summer of 1939 Heisenberg told the physicist Samuel Goudsmit that he was rejecting all opportunities to remain in America because his country needed him—a sentiment almost classically “correct.” “Do you abandon your brother because he stole a silver spoon?” he asked his friend and former student Edward Teller. If German authorities called on Heisenberg to build a bomb, would he do the “correct” thing and comply? Gradually all questions about the German bomb were transformed into questions about Heisenberg; Where was he? What was he doing? Very serious concern was the response when the scientific underground reported, through Switzerland in the spring of 1942, that Heisenberg was in Berlin and was running the German atomic-research effort.
Cut now to the spring of 1945. The Institut fur Physik has moved to southern Germany to escape the horrific bombardment of Berlin. A small laboratory and offices have been set up in the town of Hechingen. By this time the Americans are pretty much convinced that there is no German bomb program, but General Leslie Groves, the commander of the Manhattan Project, which built the American bomb, leaves nothing to chance. He has created an elite, mobile intelligence unit called the Alsos Mission to track down every kilogram of uranium in Germany, the heavy water, and the leading scientists. Still at the top of the list is Heisenberg.
When the Alsos Mission arrives in Hechingen, in late April of 1945, it finds all that remains of the German bomb program—a pathetic joke: some research papers, an unfinished pile that would never have gone critical, and a handful of the great names of German science, happy to be in American hands at war’s end. An Alsos colonel will soon round up Heisenberg, too, for six months of Babylonian captivity in England. There ten leading German scientists will first hear of Hiroshima. Clerks for the British Secret Intelligence Service, which has wired the house for sound, will patiently transcribe the expressions of amazement by Heisenberg and others at the dramatic contrast of Allied success in building a bomb, next to their own failure.
What happened?
MARK WALKER’S new history of the German bomb program doesn’t put the question quite this way, but it offers a revision of earlier accounts which is backed up by a great deal of original research in German archives, expanding on the work done by the British historian David Irving in the mid-1960s. Walker’s explanation for the German failure is starkly simple: “Army Ordnance concluded that nuclear fission was irrelevant to the war effort.”
Walker’s emphasis is on the official decision. His explanation of the reasoning behind the decision stresses the immense effort required to build an atomic bomb. This has been cited by other writers, and it’s not hard to see why: inventing the bomb was far too big a job for Germany in wartime — even the Americans, with their vast wealth, didn’t have a bomb ready to test until July of 1945, two months after Germany’s surrender. Allied bombing continually interrupted experimental work. Hitler had decreed that research be limited to projects that promised quick success, scientists didn’t know how to separate the rare isotope of uranium—U-235—needed for bombs, and there would never be enough heavy water for reactors to produce bomb quantities of plutonium. Naturally the scientists were cautious in making recommendations to Nazi officials like Albert Speer, who exercised unlimited control over Germany’s wartime economy and devoted a long evening to the subject of nuclear research in June of 1942. When Heisenberg and Weizsacker requested only a few tens of thousands of marks for their work, Speer concluded that he was wasting his time—these men had nothing to offer that might spell the difference between victory and defeat. Thereafter the German “bomb" project ticked along as a research effort to build a working reactor. Some few scientists still thought they were making a bomb, but not Speer, not Heisenberg. This account of the reasons Germany failed to build a bomb makes sense, but the reasons for the Army Ordnance decision were never spelled out in the sort of paper Walker likes best. Speer was more explicit; he said Heisenberg’s litany of difficulties convinced him that a bomb was out of the question.
The most interesting thing about dm emphasis on practical difficulties is that it very largely comes from Heisenberg. In effect, it represented his way of withdrawing from the controversy whipped up by one of the early books about the invention of nuclear weapons, Brighter than a Thousand Suns (1956), by the Berlin-born journalist Robert Jungk. The controversy centered on Jungk’s claim that the German scientists had failed deliberately, had even attempted to enlist the Danish physicist Niels Bohr. Heisenberg’s mentor and friend, in a scheme to organize something very like a silent strike by the world’s physicists to ensure that no atomic bombs would be made during the Second World War. Jungk’s claim, apparently based on his conversations with Weizsacker, sent the normally easygoing Bohr into a red-eyed fury; he wrote a searing letter to Heisenberg, and then thought better of sending it. But it was no secret to Bohr’s friends that talk of a physicists’ strike wasn’t what he remembered from Heisenberg’s visit in September of 1941. Bohr had been certain that Germany was working all out on a bomb, and that Heisenberg expected to win the war with it.
Heisenberg didn’t want to fight with his old friend Bohr. He certainly didn’t want to imply—as Jungk had—that he was in any way,a nobler, better man than the scientists who had built bombs at Los Alamos. He had declined to talk to Jungk, in order to avoid controversy and misunderstanding. Thereafter until his death, in 1976, Heisenberg patiently answered certain questions over and over again—especially those about his visit to Bohr, and his reasons for advising Speer that the bomb project was too big for Germany in wartime. Thus, gradually, the conventional history was assembled. What you got, if you read quickly, was that Heisenberg went to see Bohr to ask his advice, and if anyone asked Heisenberg’s opinion about the prospects for a bomb—as Speer did—then Heisenberg simply said he couldn’t see much chance of quick success.
MARK WALKER, WHO was a graduate student in history at Princeton when he began looking into the history of the German bomb program, has approached these questions with great care and extremely rigorous standards regarding what is acceptable as evidence. With few exceptions, if it wasn’t confided to paper at the time, Walker won’t give it house room. The result is a meticulous account of the German bureaucratic landscape in which a few dozen scientists and officials generated paper about proposals to build a bomb. Not surprisingly, ir all sounds like business as usual—everybody working for the Fatherland, in letters that close with “Heil Hitler.” Walker concedes that Heisenberg was no Nazi, but he is noticeably irritated by every suggestion that the dismal failure of the German bomb program might have had anything to do with Heisenberg’s alleged reluctance to build a bomb for Hitler.
It is Walker’s treatment of Heisenberg that most importantly revises the conventional history of the German bomb program. He thinks that version gives Heisenberg far too central a role; he dismisses Heisenberg’s encounter with Speer in a paragraph; he abandons the attempt to figure out why Heisenberg actually went to see Bohr; and he thinks Heisenberg’s own accounts of the German bomb program amount to an effort to rewrite its history after the war. This adds up to a harsh judgment.
Alongside the official history recounted by Walker, however, there is a kind of shadow history—the real life just offstage, where men struggled with conscience and friends in the small hours of the morning. The fate of the German bomb was decided there, too, not only in the committee rooms. How that argument went left scant trace in the official files, and can be reconstructed now only by the fugitive evidence of secret communications, memory, intelligence files. Walker has resolved many confusions in the history of the German bomb project, but it seems to me that he has completely missed the significance of the shadow history, a point we have often argued in letters over the past several years. In his last he invited me to spell out the questions that divide us in a review. There are two that matter: Did Heisenberg’s advice play a significant role in dashing official hopes for an atomic bomb? And if so, why did he give that advice?
Pieced together, the fugitive evidence sketches in a secret history of the German bomb program, most of it long hidden by the three groups that knew about it at the time—a handful of scientists around Heisenberg, a similar group who worked at Los Alamos on the American bomb, and the British and American intelligence officers who tried to keep track of the Germans. Leading members of all three groups survive. The Germans have given only partial or elliptical accounts of what they did, apparently because they thought—perhaps overcautiously—that a true account would draw down a lifetime of emotional charges at home that they conspired to delay the German bomb program, and to pass on secret messages about it to the Allies. The British have provided little detail about what they knew at the time, because it came largely from intelligence contacts with German scientists, some of them still alive. The British also sometimes refused to share the sources of their secret knowledge with the Americans. As a result the Americans retained exaggerated fears of a German bomb program until late in 1944 and, prompted by those fears, mounted secret operations of a questionable nature which some of those who were involved still find it hard to discuss. Several scientists in the American bomb program knew about these operations. Thus all three groups that know best what happened have refused to speak clearly or openly.
An unambiguous sign of the crippling level of disaffection among the forty or fifty German scientists who took part in the nuclear research effort is the fact that at least seven of them were sources of information reaching Allied intelligence authorities. This constitutes an astounding failure of security; by way of contrast, not a single reliable report of the British-American bomb project ever reached German intelligence from any source, much less from a scientist actually involved in the project. This constitutes an astounding failure of security. These seven did not constitute a conspiracy, and did not always act in concert, but they all knew and talked to one another and shared an intense distress at the thought of Hitler with a bomb. For our purposes the most important and explicit of the reports from Germany was delivered to a physicist at Princeton University, Rudolf Ladenburg, in April of 1941. He passed it on to a Washington official in a handwritten note as follows:
It may interest you that a colleague of mine who arrived from Berlin via Lisbon a few days ago, brought the following message: a reliable colleague who is working at a technical research laboratory asked him to let us know that a large number of German physicists are working intensively on the problem of the uranium bomb under the direction of Heisenberg, that Heisenberg himself tries to delay the work as much as possible, fearing the catastrophic results of a success. But he cannot help fulfilling the orders given to him, and if the problem can be solved, it will be solved probably in the near future. So he gave the advice to us to hurry up if U.S.A. will not come too late. (I am indebted to Stanley Goldberg, a historian of science who is currently researching a biography of Leslie Groves, for the discovery of Ladenburg’s letter. After much agony I myself found the identities of the source and intermediary in the usual place— that is, in plain sight.)
The message in Ladenburg’s letter was no vague rumor passed on by the friend: the “reliable colleague” in Berlin was Friedrich Georg (“Fritz”) Houtermans, a considerable figure in twentieth-century physics, who discussed the bomb program at length with both Heisenberg and Weizsacker in 1940— 1941. Theoretical work by Houtermans predicted that a fissionable new element, later named plutonium, would be created in a chain-reacting pile. To make a long scientific story short, this discovery opened the road to a German bomb, just as the same discovery, made at about the same time in the United States, did for the Americans.
Houtermans, Heisenberg, and Weizsäcker agreed among themselves to say nothing of the discovery to military authorities, who did not learn of it from other quarters until the end of 1941—a delay of at least six to nine months. Ladenburg’s letter is not reproduced in Walker’s book, and it is hard to see how he could maintain his position if he were to take it into account. No one quarrels with Heisenberg’s claim that he told officials that a bomb program was too big a job for Germany in wartime; the question is why he said it. The letter, based as it is on a report from an intimate of Heisenberg’s during the critical first eighteen months of the German program, represents an indigestible fact for anyone claiming that Heisenberg discovered his hostility to Hitler only at war’s end.
Heisenberg was never in charge of the German bomb program, in the sense that J. Robert Oppenheimer was in charge of the American program, but he was its leading theoretician, its moral center of gravity, and a man to whom officials like Speer turned for authoritative advice. Some of Heisenberg’s closest friends and colleagues in the research effort—Erich Bagge, for instance—thought they were all “trying to build a bomb” and would have been horrified at the suggestion that Heisenberg would do anything not perfectly “correct.” Bagge does not know quite what to make of Heisenberg’s visit to Bohr in September of 1941; the two men were old friends, surely, but to discuss a secret German military program with a scientist from an occupied country—that would most positively not be “correct.”
Walker is quite right to emphasize that Bohr and Heisenberg have very different memories of what was said at their famous meeting. But the dispute has obscured a most important fact: the two men agree that Heisenberg told Bohr that Germany was engaged in a research effort to build atomic bombs. This was by far the single most important fact about the German effort, just as the most important secret about the Allied program, fanatically guarded by General Groves, was the fact that it existed.
Heisenberg not only told Bohr about the German program, he also drew for him a rough sketch of German designs for a reactor—a fact that Walker omits. These revelations were no mere theoretical breach of security; Bohr later passed on what he had learned to Allied intelligence officers, and discussed Heisenberg’s sketch with scientists at Los Alamos. This was not an isolated incident: on at least one further occasion Heisenberg discussed German nuclear research with a scientific friend outside Germany—in 1942, with Gregor Wentzel in Switzerland; and he was possibly the source of a report reaching the British from Stockholm. But even on their own, the two incidents cited here—Houtermans’s report to the United States and Heisenberg’s visit to Bohr—make it difficult to take at face value Heisenberg’s carefully worded claims that his advice to German authorities represented his own disinterested judgment based on the science involved, pure and simple. A fairer interpretation would be that Heisenberg opposed the German bomb project, his prestige gave him an opportunity to tamp down official interest, he took that opportunity, and it worked.
But, of course, none of the shadow history found its way into official German files. If it had, Heisenberg probably would not have survived the war. Does the shadow history matter? Is there any point at this late date in urging reluctant survivors to give a fuller account than they have of what they did nearly half a century ago? Those involved all seem content to live with the version of events presented with such care by Walker. The Germans have always wanted to do science, not argue with those who might charge that they betrayed their country. American intelligence officers do not want to discuss operations that seemed justified in the urgency of wartime. Allied scientists who knew about those operations regret their role now. The shadow history is painful for them all.
But of course it does matter. The fear of Hitler with an atomic bomb is what brought the bomb into the world. It was not dumb luck that saved us from the nightmare, or the frantic American race to build a bomb of our own, but the fact that a handful of German scientists—Heisenberg first among them—found a way to guarantee that the German bomb died in utero.