1939 Einstein’s Letter

July 16, 1939

On August 6, 1945, an American B-29 named the Enola Gray released a 9,000 atomic bomb on Hiroshima, Japan. On August 8, Russian army units invaded Manchuria and Korea. The next day the United States dropped a second atomic bomb, this time on Nagasaki. The world had entered the nuclear age.

President Truman’s decision rocked the world.  While historians debate the necessity of using such force on civilian populations, few doubt that the weapon would have been developed had it not been for the persistence of a Hungarian-born physicist named Leo Szilard and his famous colleague, Albert Einstein.  Sometimes a letter can change the world.

Leo Szilard

After serving briefly in World War I, Szilard moved to Berlin to study physics. Before 1933 Germany had won ninety-nine Nobel Prizes for science, compared to eighteen for England and only six for the United States. By the 1920s the Nazis’ rise to power carried with it a growing anti-Semitism. The Nazi secret police published weekly attacks on prominent Jewish scientists. Szilard saw the writing on the wall and fled to Vienna, and later to London, where he headed an effort to bring refugee scientists to British universities.

In 1933, the year Hitler came to power, Szilard had a revelation while sitting at a traffic light in London, that it might be possible to split a nucleus with a neutron to create a chain reaction of energy known as nuclear fission. In 1939, two German physicists Otto Hahn and Fritz Strassman successfully bombarded a single uranium atom with a neutron beam, splitting the atom in half and releasing an intense burst of energy.

The news both elated and scared Szilard. He knew that soon be able to get his hands on a weapon of unlimited power.  Also he learned that Germany was blocking exports of uranium from occupied Czechoslovakia. Since Belgium possessed the only other known stockpile of uranium, he need to warn the government not to export uranium to Germany. But Szilard was relatively unknown and it was doubtful anyone in the Belgium government would listen to him.

Albert Einstein

Szilard had worked with Albert Einstein in the 1920s. Together they patented a refrigerator pump that would later be used in nuclear reactors. Einstein was not just a leading scientist of his day, he was also a musician and a very popular man socially. It happened that Einstein was a close friend of the queen of Belgium. She played piano while Einstein played his violin. Einstein had stood up against the Nazis and became one of their favorite targets.

On July 16, 1939, Szilard and a colleague, physicist Eugene Wigner, drove to have a visit with Einstein where he was staying on Long Island. Einstein agreed to their proposal immediately but decided it was better to direct the letter to the Belgian ambassador than the royal family. A copy of the letter was sent to the State Department so Washington would not think they were meddling in military matters.

The Manhattan Project

Within days Einstein wrote a letter to President Franklin Roosevelt to  be delivered by the economist Alexander Sachs, a friend and adviser to the President. It was quite some time before Sachs could approach Roosevelt and the meeting did not go well. Sachs went back to his hotel and took a shower and resolved to go back to the White House once more. This time he started with a story about how Napoleon lost an opportunity to have a fleet of steamships. The lost opportunity cost him his empire. This story got Roosevelt’s attention and the result was the Manhattan Project which developed the atomic bomb.


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