So my history class is studying WWII and discussing the atomic bomb, so I thought I'd repost an older one here on Einstein's Letter to FDR (which I make my students read).
Einstein's First Letter in August of 1939 told President Roosevelt of the possibility of a nuclear bomb and that Germany might be also working toward this goal:
In the course of the last four months it has been made probable through the work of Joliet in France as well as Fermi and secularity 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 letter garnered a quick response from FDR, who replied in October that he had acted on Einstein suggestions:
I found this data of such import that I have convened a Board consisting of the head of the Bureau of Standards and a chosen representative of the Army and Navy to thoroughly investigate the possibilities of your suggestion regarding the element of uranium.
In March of 1945, Einstein wrote to FDR again, this time telling him that there were problems between the scientists and the government officials the President had appointed:
The terms of secrecy under which Dr. Szilard is working at present do not permit him to give me information about his work; however, I understand that he now is greatly concerned about the lack of adequate contact between scientists who are doing this work and those members of your Cabinet who are responsible for formulating policy.
Einstein's suggestions to FDR resulted in the creation of the atomic bomb, which President Truman dropped on Japan in August of 1945.