ESSAY by David C. Cassidy
Germany and the Bomb: New Evidence
hy didnÕt Germany build an atomic bomb during World War II? This question has yielded
divergent answers over the past 48 years. After the war, German scientists were unwilling to admit any support of German war aims but were eager to bring their nation into the nuclear age with a nuclear power program under their own direction. They therefore argued that their failure was not a scientiÞc one but was the result of wartime shortages and their own lack of will. Some even hinted at a moral rejection of building bombs for Hitler. Allied scientists, in contrast, had to confront the unwanted results of their achievementÑ the onset of a nightmare era of nuclear cold war and military control of research. They consoled themselves that they had done their work in what they believed to be a race against an eÝort to put a nuclear weapon in HitlerÕs hands: if the Germans had failed, they argued, it was not for lack of trying.
The long-awaited release to the public in early 1992 of secretly recorded conversations among 10 German atomic scientists has inspired yet another round of divergence. The scientists were held in Allied captivity after World War II at an English country estate, Farm Hall, near Cambridge, and their conversations were recorded by microphones hidden in the rooms at Farm Hall. Among the 10 were Otto Hahn, codiscoverer of Þssion, Walther Gerlach, physicist and administrator of the German atomic project, and Werner Heisenberg, scientiÞc head of Þssion research.
The newly released conversations indicate that the scientistsÕ account originated in the shocked aftermath of the news that the U.S. had dropped an atomic bomb on Hiroshima on August 6, 1945. The captive Germans had thought themselves ahead of the Allies all along. Realizing that the Allies did have the bomb, their conversation turned to two main issues: How did it work? and Why had Germany not achieved a nuclear weapon? After a night of agonizing by all, Heisenberg and Gerlach prepared a press release articulating the scientistsÕ oÛcial position.
The documents recently released are not the original tapes or even transcripts of them. They are biweekly intelligence reports to Washington, containing idiomatic British translations of excerpts
of the conversations. The 270 pages of text had long been available to several key intelligence Þgures, most notably Samuel A. Goudsmit, who used them in his 1947 account of Allied intelligence about the German atomic eÝort, Alsos. Nor are the newly public reports the only materials available from Farm Hall. Over the years, a diary, numerous letters and the press release written by the scientists while at Farm Hall have come to light. What is diÝerent is that, for the Þrst time, the public has access to a record greatly enriched by the scientistsÕ unguarded conversations. Against the backdrop of the wartime record, the material just released enables a clearer insight into the diÛcult question of the German failure and into the origins and ultimate inaccuracy of the German scientistsÕ postwar account.
Two sharply diÝering interpretations of the Farm Hall debates have recently appeared in the U.S.
Stanley Goldberg and Thomas Powers, writing in the Bulletin of the Atomic Scientists, support the German position as it evolved at Farm Hall and even go several steps further: Heisenberg delayed the eÝort, hid their progress from the authorities and leaked information to the Allies. Jeremy Bernstein, writing in the New York Review of Books, Þnds general support for GoudsmitÕs earlier assessment: the German scientists did not know how an atomic bomb works and raised morality as a foil for their failure.
One potentially decisive question has always been: How much of the Þssionable but rare isotope uranium 235 did Heisenberg think would be needed for a bomb? If it were a relatively small amount (which it is), they could have obtained it if they had really tried; a large amount would undercut the need for scruple. ÒQuite honestly,Ó Heisenberg tells Hahn at Farm Hall, ÒI have never worked it out, as I never believed one could get pure 235.Ó But Heisenberg did know that a reactor would breed the easily extracted plutonium, which could also power a bombÑleaving the question of scruple here unresolved.
While Bernstein faults Heisenberg on other facets of bomb research, Goldberg and Powers press their case for sabotage. Their main evidence beyond Farm Hall is a newly found thirdhand intelligence report reaching Washing-
120 SCIENTIFIC AMERICAN February 1993
ton in April 1941. It stated that Germany was working on a bomb under Heisenberg but that Heisenberg delayed the work, fearing Òthe catastrophic results.Ó There is, however, no evidence of any delay at that time. In fact, in a February 1942 meeting with regime oÛcials, Heisenberg readily explained that a reactor could be built, that an atomic explosive was possible and that the reactor would breed plutonium.
Yet Heisenberg was reticent in a June 1942 meeting with Albert Speer, HitlerÕs head of wartime industrial production. Reports of the meeting suggest that Heisenberg did not mention plutonium as a reactor by-product. Speer was satisÞed enough with the prospect of a novel energy-producing device to continue modest support, while concentrating funds on the development of rockets and jet aircraft.
Why were Heisenberg and his colleagues suddenly less forthcoming? In my opinion, the answer entails neither scruple nor stupidity, but technology and circumstance. Speer was gearing the German economy for total war. If the scientists had hinted that they could produce a bomb, the regime would have established a crash program. Failure to produce in short order (a likely outcome) would have had severe consequences. Believing themselves far ahead, the physicists felt that an explicit bomb program was unnecessaryÑyet within their grasp if they so desired it. Moreover, by encouraging only modest reactor support, the German scientists received everything they wanted: Þnancing, recognition, control over the project, protection from ideological attack and reduced risk of assignment to the front coupled with an opportunity to support the German cause. War conditions soon made their decision irreversible.
In the shadow of defeat, the Nazi atrocities and the Allied achievement, the Farm Hall scientists suddenly found the reasons just outlined to be a politically untenable explanation for their wartime failures. They responded with an account of the past tailored to their present situation: moral scruple compounded with administrative and material limitations far beyond their control.
DAVID C. CASSIDY is an associate professor at Hofstra University. His book Uncertainty: The Life and Science of Werner Heisenberg was recently released by W. H. Freeman and Company.
Copyright 1993 Scientific American, Inc.