A month before Hitler invaded Poland, two Hungarian physicists - exiled Jews into America - persuaded Albert Einstein to write a 'historical' letter about some courious properties of a new element to which Einstein himself had little knowledge, and post it to the president of the U.S.
Nassau Point, Peconic, Long Island
August 2nd, 1939
President of the United States
Some recent work of Enrico Fermi and Leo Szilard which has been communicated to me in manuscript leads to me expect that the element uranium may be turned into a new and important source of energy in the immediate future. 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 become 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 (...) by which, my dear President, it might be possible to unleash an immense destructive force.
Roosevelt found that letter intriguing but -for two years- it was kept in a drawer.
A couple of months before Pearl Harbour, the president ran across the letter, looked thoughtfully at it over, formed a committee, set aside some executive funds that needn't the approval of Congress, and conducted a small exploratory study. The result was a mushroom cloud in the New Mexico desert.
After that first thermonuclear trial blast at Alamogordo, the U.S. president was convinced the relativity theory father guessed correctly what concerned to chain reactions , and went enthusiastically ahead to prove beyond any doubt the matter of those hypothetical destructive properties .