The nightmare that the Nazis might succeed in building an atomic bomb dominated the minds of the British and US governments in the later stages of the war. When the first V2 rockets exploded without warning in London in 1944, anxious scientists arrived quickly at the detonation sites with Geiger counters to see if the warheads contained radioactive material. At the Normandy landings on D-Day, anti-radioactivity squads stood by in case the Nazis attacked with novel weapons.
Concern was so high that the American Alsos scientific mission followed invading allied troops into occupied Germany, sniffing out evidence of nuclear development, and following the slimmest clue. In the captured western zone Alsos found a prototype reactor using graphite and heavy water together with uranium cubes – but no weapons. The mission reported that Germany lagged behind and fears of a Nazi atom bomb were groundless. The Allies relaxed.
But the Americans and British were not the only people scouring Germany for evidence of atomic development. Joseph Stalin demanded his army commander in chief, Marshall Zhukov, investigate in the captured eastern zone and report back. The Zhukov report, recently released from former Soviet archives, tells a different story.
In November 1944 an agent of Soviet military intelligence, the GRU, reported German preparations to test a new bomb of enormous destructive capacity in Thuringia. The agent included technical details and drawings and reported the bomb was one and a half metres in diameter and consisted of interconnected hollow spheres. In general aspect the device described bears some resemblance to the Trinity bomb. Professor Vladimir Sacharow, a military historian at the University of Moscow says a second GRU report, from 23 March 1945, spoke of an enormous test explosion in Thuringia that incinerated everything inside a 600 yard radius, leaving radioactive traces.
Based on these and other reports, the Zhukov Report to Stalin reached a very different conclusion from the Alsos team. It said that, ‘The Germans achieved good results in the theoretical and practical research into the application of atomic energy which resulted in the construction of an atomic bomb.’
The Germans are known to have imported 1,000 tons of uranium through Belgium, from the Belgian Congo, and it is sometimes thought the need to import uranium was what hampered Nazi scientists. But as Vladimir Sacharow points out, the Joint German-Soviet mining company Wismut extracted uranium from Saxony and Thuringia between 1946 and 1990 that was the basis for the entire Soviet nuclear programme and was the third largest producer of uranium in the world.
The research reactor Alsos discovered was hidden in the cellar of an ancient castle in the small town of Haigerloch. It had been dispersed away from cities likely to be subject to air attack, by the SS, who were in charge of all secret weapon development by 1944. From recent research, it now seems clear the SS dispersed more than one nuclear research facility in this way, some to purpose built underground laboratories, others to more obvious places.
Kummersdorf, near Berlin, was the home of German rocket and secret weapon development since the early 1930s. It became the Army weapons testing range. Alsos discovered an experimental nuclear reactor here that had been destroyed, possibly in a nuclear accident.
More significantly, in September 1943 work was begun on Projekt Riese, or Giant, which involved the construction of a number of massive underground complexes in the Sowie Mountains of Lower Silesia, with some kind of special facilities. The project was originally under the control of Reichsminister Albert Speer but, by April 1944, Hitler was so frustrated at the slow progress he handed the project over to the SS and to General Hans Kammler to complete. The work was on a huge scale with thousands of metres of tunnels and work areas. Construction took so many people Kammler built a concentration camp next door to house them. The man put in charge scientifically was Professor Walther Gerlach, who was a nuclear physicist and the man responsible for Germany’s atomic weapons programme. And from the few documents of the project, we know it was classified as “Kriegsentscheidend” – Decisive for the outcome of the war – the highest classification for secrecy and funding priority in Nazi Germany.
Did the Alsos team look hard enough? And did they look in the right places? Or were they too easily satisfied? And was the Zhukov report correct in saying there was a German atomic bomb?
In the west, the accepted story of German nuclear development in World War II goes something like this. Hitler didn’t even come close to developing an atomic bomb. Germany lost many of its brilliant scientists because they were Jewish and fled to Britain or America. Those German scientists who remained were way behind their counterparts in Britain and the U.S. and were in any case half-hearted about working on a bomb for Hitler. They lacked the industrial muscle to separate Uranium 235 (weapons grade material) on an industrial scale, like the Manhattan project, and didn’t even manage to build a working nuclear reactor.
This is in some ways a comforting narrative – one that is much easier to deal with than trying to envisage London or New York after a nuclear explosion, and Britain and the U.S. on their knees begging Hitler for mercy. But how accurate is it?
Many German Jewish scientists did seek refuge in Britain and America. But the scientists that stayed behind were first rate minds and included those who had made the initial discoveries about nuclear fission. Indeed, in its infancy, nuclear energy was very much a German science. Nuclear fission was discovered in April 1939 by Otto Hahn and his assistant Fritz Strassman. Both continued to work at the Kaiser Wilhelm Institute throughout the war on nuclear chemistry, though neither worked specifically on a nuclear weapon. Werner Heisenberg, Germany’s most illustrious physicist was appointed by the Wermacht to run the Kaiser Wilhelm Institute, which they took over, and led nuclear research.
The idea that many German scientists were covertly anti-Nazi is a discovery that they made after the war when they were in Allied hands. For example, In 1941, with Germany master of all western Europe, Heisenberg told Nils Bohr (a Dane) ‘How important it was that Germany should win the war . . . the occupation of Denmark, Norway, Belgium and Holland was a sad thing but as regards the countries in eastern Europe it was a good development because these countries were not able to govern themselves.’
Clearly, some German scientists saw the highest good of Europe in a German victory and German hegemony.
Heisenberg told a conference of the Reich research Council as early as February 1942, ‘If one could assemble a lump of uranium-235 large enough for the escape of neutrons from its surface to be small compared with the internal neutron multiplication, then the numbers of neutrons would multiply enormously in a very short space of time, and the whole uranium fission energy, of 15 million-million calories per ton, would be liberated in a fraction of a second. Pure uranium-235 is thus seen to be an explosive of quite unimaginable force.’
Conscious of this potential, in the first months of the war, German scientist voluntarily got together to form the Uranverein – the ‘Uranium Club’ – and set out to explore whether nuclear fission could be used either for energy in a reactor, or in a weapon, or both. At this stage, it would have been perfectly possible for Germany to acquire a bomb first. America was only galvanised into action by the report from Nobel laureate Arthur Compton who estimated that, with access to a uranium-heavy water reactor running at 100,000 kilowatts for two months, the Germans could have enough plutonium for six atomic bombs by the end of 1942.
In 1940, the Nazis began building a new laboratory for nuclear research next door to the Institute for Physics in Berlin. It was named the Virus House to discourage attention. Other research teams were experimenting elsewhere in Germany including the University of Leipzig. The Uranverein physicists had access to thousands of tons of refined uranium and to substantial quantities of heavy water from Norway. They were building their first cyclotron in Joliot-Curie’s captured laboratory in Paris. And they had many of their greatest physicists and chemists working on the problem of U-235 separation.
In June 1942, Werner Heisenberg and Robert Dopel built a uranium-heavy water reactor in the laboratory in Leipzig and succeeded in demonstrating a sustained fission reaction – the first scientists in the world to do so. They also demonstrated the world’s first nuclear disaster because after 20 hours of continuous operation, the reactor exploded, destroying the laboratory, the scientists fleeing from the building just in time to save their lives.
Would Hitler have used an atomic bomb had he possessed it? Albert Speer had no doubt. In his autobiography Inside the Third Reich, he wrote ‘I am sure that Hitler would not have hesitated for a moment to employ atom bombs against England.’
What if the Leipzig reactor hadn’t exploded but continued in operation? What if other similar reactors were built – at Kummersdorf or in the Sowie mountains – and Uranium-235 or Plutonium did become available in Germany? This is a scenario that few people cared to investigate or contemplate in any detail – then and still today. It is a scenario that I’ve given a fictional outing in my novel When Sally comes marching home.