A new weapon of immense power had been unleashed on the world, aided by scientists under the misconception that Nazi Germany was about to develop a nuclear weapon itself. The weak state of the Nazi program was partly due to a secret pact by key German physicists. Scientists working on the US program, however, were kept uninformed of the actual state of the Nazi program.

In August 1939, in the approach to World War II, Albert Einstein signed a letter to US President Franklin D. Roosevelt stating that through recent work in nuclear physics “it may become possible to set up a nuclear chain reaction in a large mass of uranium ... This new phenomenon would also lead to the construction of ... extremely powerful bombs.” The letter stated that “Germany has actually stopped the sale of uranium from the Czechoslovakian mines which she has taken over”, and called for a “watchfulness and, if necessary, quick action on the part of the [US] Administration”.

It was not the threat of Germany at war, but the threat of the German regime having uncontested control of the atomic bomb that caused concern to a number of nuclear physicists, including several refugees from Nazism. The “Einstein letter” was organised by one such physicist, Leo Szilard, and presented to Roosevelt on October 11, 1939. “I really only acted as a letter-box. They brought me a letter all ready for signature and I simply signed it”, Einstein later explained to biographer Antonina Vallentin.

Szilard was afraid of Nazi Germany getting the atomic bomb, but hadn’t been able to convince the US government that the new weapon was practical. In Brighter Than a Thousand Suns, published in 1959, Robert Jungk examines the events surrounding the US nuclear program. He details the actual state of nuclear weapons’ development in Germany at that time and shows that Hitler’s forces were nowhere near developing the atomic bomb.

“Four factors must have combined to frustrate the construction of a German atom-bomb. In the first place the absence of eminent physicists driven into exile by Hitler now proved to be a severe handicap. Secondly, the poor organisation by the National Socialists of research in the interests of war and its inadequate recognition by their Government, and thirdly, the technical difficulties of so complex a project, were further obstacles. But above all, in the fourth place, the actual personal attitudes of the German experts in atomic research who had remained at home counted against success.

“Fortunately they did nothing to facilitate the construction of such a bomb in the face of misunderstanding by the authorities and the insufficient technical resources the latter provided. On the contrary, such physicists were able successfully to divert the minds of the National Socialist Service Departments from the idea of so inhuman a weapon.”
Jungk describes how several groups that could have followed up the possibility of developing nuclear weapons came not to. He states, “there were at that time [at least 13] prominent German physicists who had agreed that they must try to avoid working with Hitler’s war-machine or to make only a pretence of doing so. The names of German physicists unwilling to supply Hitler with supplementary armaments were deposited, after the war had begun, in Sweden - with Professor Westgren - and in Holland - with Professor Burgers. It was considered that an open ‘strike’ of research workers would be dangerous, as it would leave the field open for unscrupulous and ambitious persons.”

Einstein later stated that, “If I had known that the Germans would not succeed in constructing the atom-bomb, I would never have moved a finger”.

By 1941 reports were getting through to the US government that Hitler had no advanced bomb project. These reports, which came from scientists fleeing Europe, were not conveyed to the physicists working on the US bomb project, who believed right up to the final defeat of the Nazi regime that Germany might have been ahead of the US in developing nuclear weapons.

While the scientists were unaware of the weak state of the German nuclear program, the US government knew the reality, including through reports of German scientists’ non-cooperation. The US program was the largest engineering work undertaken to that time, and a strong Nazi program would have had a similar requirement. (While Britain and Canada participated in the US program, they were abruptly excluded at the end of the war.) At Oak Ridge, Tennessee, the longest factory halls in the country were constructed. At Hanford, in Washington State, it took 60,000 workers to build one of the largest chemical works in the country. At Los Alamos, in New Mexico, seven separate divisions worked on the final product. In total, the bomb took 150,000 people to build.

The German regime was defeated before the first nuclear weapon was ready for use. Nevertheless, the US bomb project maintained its frantic activity. The bomb project organiser at the Los Alamos centre, General Leslie Groves, continually urged, “We must not lose a single day”.

The only possible target now was Japan, which could not possibly have been developing nuclear weapons (although supporters of the US nuclear bombing of Japan occasionally claim that there was a Japanese nuclear weapons program). The explanation given for the bomb’s use therefore became the need to reduce US losses in the final invasion.
The use of nuclear weapons was now advocated on the grounds of expediency. For scientists such as Einstein this wasn’t valid, regardless of issues of the war itself. An army at any time can argue for new weapons to defeat its enemy, but once a fundamentally new weapon has been achieved, the threat to the whole of humanity is permanently increased.

The expediency argument could be used today in relation to new technologies, including biological weapons, robotics and nanotechnology. The US could argue that to reduce its own casualties when fighting “terrorist” opponents it should deploy biological weapons (which it hasn’t argued), or develop autonomous killing machines for use in battle conditions (which it has announced plans for within the next decade). Each such step makes the world a more dangerous place.

Szilard, who had earlier organised the letter to Roosevelt, now organised another letter from Einstein to the President, warning of the threat that the nearly completed bombs would pose. Szilard also organised a petition of scientists working on the bomb project opposing its use, which gained 67 signatures before it was banned. Jungk quotes Szilard, explaining the attitude of the scientists he was speaking for at this time: “During 1943 and part of 1944 our greatest worry was the possibility that Germany would perfect an atomic-bomb before the invasion of Europe ... In 1945, when we ceased worrying about what the Germans might do to us, we began to worry about what the Government of the United States might do to other countries.”

The US was in a race against time to drop the bomb before the war ended. From mid-July 1945, the US forces were able to read coded Japanese military information, including expressions of the view that Japan was beaten. At the same time, the US Air Force could bomb just about any target it wanted. Given these and other descriptions of the state of Japan’s defences and the attitude of Japan’s rulers, there was no military reason for the US government to bring into play a devastating new weapon.

The 1945 nuclear attacks on Japan resulted in the deaths of 250,000 people and ongoing damage generations later. The two cities presented different technical challenges: a flat coastal area and a rugged terrain. Two different bomb designs were used; one based on uranium and the other on plutonium. After a list of possible Japanese cities for nuclear bombing had been drawn up, these cities were deliberately spared massive conventional bombing so that the effect of a single atomic blast could be more accurately assessed.

Einstein gave his view of the development of the first nuclear weapon in a December 10, 1945 speech titled: “The war is won, but peace is not”.

“We helped in creating this new weapon in order to prevent the enemies of mankind from achieving it ahead of us, which, given the mentality of the Nazis, would have meant inconceivable destruction and the enslavement of the rest of the world. We delivered this weapon into the hands of the American and the British people as trustees of the whole of mankind, as fighters for peace and liberty. But so far we fail to see any guarantee of peace, we do not see any guarantee of the freedoms that were promised to the nations in the Atlantic Charter. The war is won, but the peace is not ...

“The world was promised freedom from fear, but in fact fear has increased tremendously since the termination of the war. The world was promised freedom from want, but large parts of the world are faced with starvation while others are living in abundance.”