In August 1939, with Nazi Germany's Third Reich about to escalate Europe into all out war, Albert Einstein took it upon himself to point the United States towards advancements in nuclear fission using Uranium -- that large amounts of power could be produced by a chain reaction and that, by harnessing this power, the construction of "extremely powerful bombs" was conceivable.

While US President Franklin Delano Roosevelt was still considering whether to get involved in the events unfolding in Euriope, it didn't take long for the gravity of the scientific discovery to take root, even though the apparent inaction following the letter had led some to believe the president wasn’t interested in what the physicist had to say.

Roosevelt wrote back to Einstein in October after meeting Alexander Sachs (Wall Street economist, friend and advisor to the president), informing the physicist that he had set up a committee consisting of civilian and military representatives to study uranium. This is the committee that would go on to become the infamous Manhattan Project, and deliver America a working atomic bomb.

It is thought that before Einstein's letter (drafted with the help of Hungarian physicist Leo Szilard) and the involvement of Sachs, FDR may have been dismissive of atomic energy, and the Nazis might have beaten the US to the first atomic weapon.

In 1938, two German chemists — Otto Hahn and Fritz Strassmann — discovered the process of nuclear fission. Fission is a reaction in which the nucleus of a heavy atom splits into two or more smaller nuclei, releasing incredibly large amounts of energy. Almost immediately, Nazi scientists were provided funding to realize the idea of a “super-weapon” that could harness the chain reaction of nuclear fission. It is a sobering thought of what might have happened had Hitler’s scientists had beaten the US in the race to weaponising the atom — thanks to German disorganization and persecution, the Nazi nuclear weapon program was dead in 1942.

The eventual bombing of Japanese cities of Hiroshima and Nagasaki in 1945 and the subsequent Cold War deterrent of "mutually assured destruction" may have played out differently as well had Einstein not written his letter to Roosevelt — perhaps setting humanity on an entirely more destructive, potentially world-ending path.

Read the full contents of the letter below.

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Albert Einstein
Old Grove Road
Peconic, Long Island
August 2nd, 1939

F.D. Roosevelt
President of the United States
White House
Washington, D.C.

Sir:

Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. Certain aspects of the situation which has arisen seem to call for watchfulness and if necessary, quick action on the part of the Administration. I believe therefore that it is my duty to bring to your attention the following facts and recommendations.

In the course of the last four months it has been made probable through the work of Joliot in France as well as Fermi and Szilard in America--that it may be possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future.

This new phenomenon would also lead to the construction of bombs, and it is conceivable--though much less certain--that extremely powerful bombs of this type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove too heavy for transportation by air.

The United States has only very poor ores of uranium in moderate quantities. There is some good ore in Canada and former Czechoslovakia, while the most important source of uranium is in the Belgian Congo.

In view of this situation you may think it desirable to have some permanent contact maintained between the Administration and the group of physicists working on chain reactions in America. One possible way of achieving this might be for you to entrust the task with a person who has your confidence and who could perhaps serve in an unofficial capacity. His task might comprise the following:

a) to approach Government Departments, keep them informed of the further development, and put forward recommendations for Government action, giving particular attention to the problem of securing a supply of uranium ore for the United States.

b) to speed up the experimental work, which is at present being carried on within the limits of the budgets of University laboratories, by providing funds, if such funds be required, through his contacts with private persons who are willing to make contributions for this cause, and perhaps also by obtaining co-operation of industrial laboratories which have necessary equipment.

I understand that Germany has actually stopped the sale of uranium from the Czechoslovakian mines which she has taken over. That she should have taken such early action might perhaps be understood on the ground that the son of the German Under-Secretary of State, von Weizsacker, is attached to the Kaiser-Wilhelm Institute in Berlin, where some of the American work on uranium is now being repeated.

Yours very truly,

Albert Einstein

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