The Race for the Atomic Bomb in World War II

We generally think that major wars are accelerators of technical progress, and the Second World War is often cited in this respect. But what happens if a major technological breakthrough that everyone knows, hopes or fears is imminent, a breakthrough that would lead to an absolute weapon capable of completely overturning the geopolitical balances in place?

What if, to put it bluntly, it was the atomic bomb that had started the Second World War, rather than simply bringing it to a close?

A reading of Rainer Karlsch’s book Hitler’s Bombe, the French translation of which was published in 2007 by Calmann-Lévy, highlights the following important points.

I – Discovering the principles of nuclear energy

1931 – Discovery of heavy water (D₂O) by the American Harold C. Urey. p.59

1932 – First nuclear fusion experiment in Cambridge, led by Ernest Rutherford, assisted by Paul Harteck (Austrian) and Mark Oliphant (Australian). P.39

1938 – Shortly before Christmas, Otto Hahn and Frtitz Strassmann achieved the first fission of the uranium atom. They had wanted to create radium by bombarding uranium with neutrons, but instead of detaching a few particles of uranium, they had split the atoms into two parts. Otto Hahn was considered the best radiochemist of his time, and was awarded the Nobel Prize for Chemistry in 1944 for his discovery of fission. p.38

1939 – On 6 January, Hahn and Strassmann published the results of their series of tests. Their sensational findings spread throughout the world community of physicists. The most fascinating aspect of this new kind of nuclear reaction was the large amount of energy it released, 200 million electron volts – a gigantic figure, that is to say part of the mass of the nucleus that was released as heat and light. P.32.

1939 – 22 April, Jean-Frédéric Joliot Curie confirmed the chain reaction in the journal Nature: several fast neutrons are emitted when the nucleus of the uranium atom is fissioned by a slow neutron. p.32

II – Political and military awareness

1939 – Wilhelm Hanle held a lecture on “the creation of energy from a uranium fission machine“. He explained that it had to be built from a combination of uranium and heavy water or graphite. [heavy water or graphite must slow down the fast neutrons released by the fission of the uranium nucleus to increase the probability that they will in turn encounter a uranium nucleus for further fission]. Hanle and his mentor Georg Joos wrote a letter to the Reich Minister for Education, Bernhard Rust, in which they outlined the possible consequences of atomic energy. This included the idea of a nuclear explosive. p.33

1939 – On 24 April, just two days after Joliot-Curie’s publication, Professor Paul Harteck of Hamburg University and his assistant Wilhelm Groth reported to the War Ministry that the development of nuclear explosives was possible: “The first country to make use of fission of the nucleus will possess an irrecoverable superiority over the others“. p.33

1939 – 2 August, USA, Albert Einstein, Enrico Fermi, Leo Szilard and Eugene Wigner write to President Roosevelt, pointing out that uranium bombs could destroy entire cities. p.69

1940 – March, in Great Britain, Otto Frisch and Rudolf Peierls draft two brief memoranda to the government authorities on the construction of a superbomb.p.69

1940 – In the USSR, Georgi Flerov and Konstantin Petrzak, two students of Igor Kourtchatov, established that spontaneous fission of uranium exists in nature. Curious to see how his colleagues in the West would react to this discovery, Flerov published an article on the subject in Physical Review. To his astonishment, there was no response. Having a good sense of the imminent danger, he correctly interpreted the silence of his colleagues: uranium research had become a top-secret military affair. p.69

It is also worth noting that Frédéric Joliot-Curie was a Communist, a member of the PCF whose links with Moscow are well known.

III – A new look at the logic behind the Reich’s first territorial conquests

1938 – 12 March, Anschluss, the scientific community in Vienna arrived as reinforcements, for the German effort, leading in 1942 to the foundation of the Neutron Institute under the direction of Georg Stetter. It was one of the best-staffed and best-equipped nuclear physics centres in the entire German zone of influence. p.42

1938 – 29 September, Munich Agreement and annexation of the Sudetenland. The Joachimstahl mines, Europe’s oldest and largest uranium mines, came under German control. From then on, they supplied only German producers. p.59

1940 – 9 April, invasion of Norway. Since 1934, heavy water had been produced by the Norwegian company Norsk Hydro; it was a by-product of the manufacture of hydrogen by electrolysis. To obtain one gram of heavy water, 1000 kWh of energy had to be used. Such an expensive method could only be used as a secondary process, but in Norway, water power was cheap. No other country in the world had a comparable facility before the war. p.60

1940 – 10 May Invasion of Belgium.  The Brussels Mining Union, one of the largest uranium producers in the world, was integrated into the German uranium project. p.59

1940 – 22 June, armistice in France. The Paris cyclotron came under German control. It remained in Paris, but was used every other week by the Germans and every other week by the French. The cyclotron is an extremely important particle accelerator for fundamental research in nuclear physics. In the United States there were already around thirty before the war, but none in Germany. The Paris cyclotron was by far the most powerful source of neutrons available to the Reich. p.62

Erich Schumann and Kurt Diebner, at the head of the German atomic project, had visited the installation and studied the research documents confiscated from the French army and secret services. The war had forced the French to halt their reactor experiments, without which they would probably have been the first to build a self-igniting reactor. Their patent contained the idea of using uranium in a reactor in the shape of a sphere or cob. Diebner took up this idea only good two years later. p.63.

Diebner also took up Joliot-Curie’s idea of uranium in dice-shaped structures rather than in plates, so that the uranium in the reactor was surrounded by heavy water in all three dimensions. p.107

Of course, Germany didn’t conquer France because of a cyclotron, but if that cyclotron had been installed in Lyon or Marseille, it would no doubt have changed the demarcation line.

IV – Germany’s path to the bomb

Germany had three options: the uranium fission bomb, the plutonium fission bomb and the fusion (hydrogen) bomb. As early as 1940, there was also the concept of a reactor bomb—or dirty bomb, but there was no question of the army detonating a reactor, and the idea was immediately rejected. p.272

The uranium fission bomb was totally out of Germany’s reach, but enriching uranium to a military level requires Pharaonic industrial facilities and phenomenal energy consumption.

The advantage of the plutonium fission bomb is that the plutonium is produced in a reactor using low-enriched uranium. During the chain reaction, natural uranium 238U (non-fissile) can capture a neutron released by the fission of a 235U. The new uranium isotope decays into neptunium, which in turn can capture a neutron and decay into plutonium.

On 17 July 1940, Carl Friedrich von Weizsäcker wrote a report that stopped short at neptunium. p.74.

In August 1941, Fritz Houtermans wrote a second report that went as far as plutonium. p.78

In addition, Houtermans understood the role of fast neutrons in an uncontrolled chain reaction (in other words, in an atomic explosion).

In February 1945, at Gottow, Werner Heisenberg and his group came within a few metres of the goal. Their instruments showed a multiplication of neutrons that was almost tenfold, but this was not enough to fuel a chain reaction.  The experiment would have had to be carried out in a shape that was not cylindrical but spherical, or additional material would have had to be used, but this was available at Stadtilm. p.150.

The fusion bomb: this is the one that went as far as the test, which was successful, but not transformed to military use.

At the beginning of March 1945, the SS organised the world’s first explosion of a nuclear weapon at Ohrdruf in Thuringia, and it was a fusion bomb rather than a fission bomb. Using the shaped charge principle, the Germans had succeeded in creating a tactical H-bomb that did not require atomic ignition. A sphere containing hydrogen was placed in a cylinder, with a conventional (chemical) explosive charge at each end of the cylinder. The two charges were activated simultaneously and, according to the principle of the shaped charge, the energy of the explosions was spontaneously directed in the direction of least resistance, towards the hydrogen sphere, the shock wave creating sufficient pressure and temperature at the centre for fusion. p. 253.

The author undertook on-site measurements to trace the explosion:

Having taken note of all the clues and results of the measurements—the increased activity of caesium 137 and cobalt 60, the presence of ²³⁸U and ²³⁵U, particles resulting from a high-temperature fusion process—the scientists we consulted concluded that there were traces of a nuclear event at Ohrdruf. p. 270.

There is also the report from the GRU, the Red Army’s intelligence service, which duly reported these results to Stalin: the GRU of course had a double agent on the spot. p. 261

In fact, this test was probably not the first. We also have the testimony of Luigi Romersa, a journalist from the Corriere della Serra, who was Mussolini’s emissary and reported an experiment that took place on 10 October 1944 at Peenmünde, von Braun’s rocket island. p. 209.

Germany was well and truly on the way to a miracle weapon, and a nuclear warhead fitted to a V2 could have constituted this Wunderwaffe. Wernher von Braun denied having thought of it, but it was in the order of things: when intercontinental rockets are designed, it is not to send grenades. Moreover, as early as 1946, von Braun presented his American hosts, having just arrived at Fort Bliss, with the project for a very long-range rocket equipped with a nuclear warhead, the “Comet” p. 349.

V – Lessons learned for international technical cooperation

Without war, the world’s various powers were all likely to break through in the field of nuclear weapons, even in Japan there was talk of these miracle weapons, the danger of an irreversible upset in the balance was serious, hence perhaps the escalation towards war.

Perhaps we’ve learned our lesson nowadays, and it’s probably not for nothing that the ITER project is international.

In our opinion, this is not so much for reasons of funding or the need for a wide range of skills, but because a project like ITER can also lead to a technological breakthrough that will upset the balance of power: with international cooperation, we know that this breakthrough will be shared by everyone.