There were several reasons why Nazi Germany made little progress towards the
development of an atomic bomb, notwithstanding the understandable anxieties of
British and American leaders and their scientific advisers. First, Hitler had little or no
interest in physics. In fact, he actively disliked the discipline, regarding it as a ‘Jewish
science’. Second, the atomic bomb, even if it should prove feasible, was believed to
be strictly a long-term project, capable of producing useful results, if at all, only years
after the current war had reached its conclusion. In 1942–3, Nazi Germany was not much
interested in heavy investment in the next war. Third, Germany’s premier scientist,
Werner Heisenberg, advised Minister of Armaments Albert Speer, who duly advised the
Führer, that the atomic project faced all but insuperable technical difficulties. In
particular, he said, it would be almost impossible to gather or create the necessary critical
mass of fissionable^235 U. Heisenberg did not claim that a bomb could not be built, but he
did say that it could not possibly be built for many years, and only then at very great
expense. After the war, Heisenberg claimed that he deliberately sabotaged Nazi bomb
research by misinforming Speer about the scale of the technical difficulties; there has
been a long-running debate among scholars on the question of whether he lied in that
208 War, peace and international relations
Box 15.1The scientific and technological feasibility of atomic weapons
The scientific trail to Hiroshima and Nagasaki is clear enough. The neutron was
discovered in 1932, while in 1933 that discovery sparked realization that the
neutron could be employed to trigger an explosive chain reaction. An even more
significant scientific breakthrough was achieved in January 1939, when Otto Hahn
and Fritz Strassmann managed to achieve nuclear fission, the splitting of uranium
atoms. They demonstrated that by means of neutron bombardment the atom could
be split and a self-sustaining process, a chain reaction, of atomic fission might
be achieved. But theoretical physics and an isolated experiment were not remotely
the same as bomb building. The crucial step towards a practicable bomb was taken
when two German émigré physicists, Otto Frisch and Rudolf Peierls, working at
the University of Birmingham in Britain in March 1940, calculated the critical
mass of fissile material required for a self-sustaining fission chain reaction. They
were amazed to discover that the necessary critical mass of the isotope of uranium
(^235 U) that had to be extracted from natural uranium (^238 U) was only approximately
11 pounds. Prior to their findings, it was widely believed among nuclear physicists
that possibly as much as 30,000 pounds of^235 U would be needed. Apart from the
impracticality of extracting that much of the isotope from^238 U, any bomb that
resulted would be so large and heavy that it could be delivered only by ship. In
other words, it was thoroughly impractical as a weapon. The calculations of
Frisch and Peierls changed all that. Their calculations impressed first the British
government and then the American. In theory, at least, the atomic bomb should be
technically feasible. Another fissionable element (element 94) was discovered – or
rather made, since it did not occur in nature – on 28 March 1941 in the form of
plutonium (^239 Pu). The atomic bomb that devastated Hiroshima 6 August 1945 was
made with a critical mass of^235 U, while the Nagasaki bomb used^239 Pu.