But if, in 1939, the progress being made in nuclear physics was making waves in the scientific world, the European and American political circles remained indifferent to it. Several concerned nuclear physicists, including the vigilant Leo Szilard, embarked on an awareness raising campaign aiming to alert the political and military worlds of the considerable stakes involved by one of the belligerents possessing a nuclear weapon. But their initiatives received at best only polite interest. Szilard and his friends thus decided to deploy the means they had at their disposal to thwart German military research directly. First of all they thought of alerting the Belgian authorities not to hand over to the Germans the uranium taken from the Congolese Katanga mines. To do so Szilard counted on his friend Albert Einstein, who maintained a regular correspondence with Queen Elisabeth of Belgium. But Einstein in the end preferred to write a letter, to the United States President Franklin Roosevelt, which marked the starting point of American involvement in the atomic race. In this letter the savant suggested a speeding up of research on nuclear chain reaction, with the help of significant financial support, in order to avoid the Germans getting ahead. The rush of international events at the beginning of the war was to convince Roosevelt, who ordered the setting up of an Advisory Committee on Uranium, a liaison body between the American administration and the scientific world. At first, however, the initiative only gained modest support from the committee, many of whose members continued to believe that nuclear weapons were more the realm of science fiction than military reality. But there was firmer interest in the United Kingdom, a geographical neighbour of Germany. A working group – the MAUD committee – was created to look into the matter. In July 1941 its conclusions accepted the technological feasibility of a nuclear weapon…as long as there was an industrial investment which widely exceeded the possibilities of a country already fully committed to the war effort.

In Washington the outcome of the nuclear debate on atomic weapons remained uncertain until the morning of December 7, 1941: to general surprise, the Japanese air force bombed the American Pearl Harbour naval base, on the Hawaii archipelago in the middle of the Pacific Ocean. This ‘coup’ brought about immediate United States entry into the war and globalised the conflict. And, on January 19, 1942, President Roosevelt ordered maximum concentration on attempts to produce a nuclear weapon. From this moment on the lethargy of the first years of the war would give way to a frenetic will to produce several atomic bombs as quickly as possible. Colossal financial means were released to serve a genuine race against the clock, fed by the anxiety that the Germans would get there first. A fear which was in the end a little irrational: after Germany’s surrender it was discovered that there was no Nazi nuclear weapon, even in an embryonic state. But that would only be known later.

A concentration camp for Nobel Prize winners

In the meantime, three large nuclear project sites, genuine secret cities lived in by several tens of thousands of inhabitants and designated by the single letters W, X and Y, sprang up in a few months on American soil, from the Autumn of 1942. It is there that was undertaken the Manhattan Project, which would lead to the Hiroshima and Nagasaki bombs. One of the sites, ‘Y’, was situated near to Los Alamos, on the New Mexico plateau, at an altitude of some 2000m. The location had been chosen for its complete isolation and the possibility of carrying out nuclear testing in the immediate surroundings. Some thousand scientists set themselves up there with their families, under military surveillance, and in ultra-strict secret conditions. They lived in over crowded groups of huts, from which they could only journey (and very little) subject to severe conditions. It is that which earned the site the ironical name ‘a concentration camp for Nobel Prize winners.’

At the cost of considerable effort, the majority of the technical obstacles to the development of a nuclear weapon had been overcome by April 1945, when the Third Reich was in its last days and preparing to surrender. The use of the atom bomb was thus considered, not against a defeated Germany, but against its Japanese ally, which was putting up fierce resistance. This use, from the perspective of the new American President, Harry Truman, seemed preferable to a ground based landing followed by a drawn out and bloody stalemate. On 16 July 1945, at dawn, an immense blinding stroke of lightning ripped the air of the Jornada del muerto, a desert zone in New Mexico, followed by an enormous cloud in the form of a mushroom. The first atomic bomb had just exploded, liberating energy the equivalent of 18,600 tons of trinitrotoluene (TNT), a power up until then unimaginable for the explosion of a single bomb. The success of the test confirmed the feasibility of a rapid nuclear bombing of Japan. The reason for the American haste was not only to avoid a ground based invasion combined with heavy human casualties but also, and above all, to prevent the Soviet Union disembarking first on the Japanese archipelago, which would have led to inevitable territorial and political claims on the part of the USSR at the end of the war. An ultimatum to surrender immediately, issued on July 26, was ignored by the Japanese leaders.