The Einstein-Szilárd Letter (1939)

and the birth of the Manhattan Project

This essay is also available in audio format.

Three frames of Albert Einstein and Leo Szilárd from the documentary film “Atomic Power” (1946) for TIME’s The March of Time series

The now famous Einstein-Szilárd letter was written at the initiative of Hungarian nuclear physicist Leó Szilárd with help from Edward Teller and Eugene Wigner in 1939. It was signed by Albert Einstein and sent to the President of the United States, Franklin D. Roosevelt in October 1939. The letter argued that the United States should engage in uranium research. Its writing was motivated by the news of the discovery of uranium fission by Otto Hahn and Fritz Strassmann nine months prior.

The letter prompted Roosevelt to propose the undertaking which would later become the Manhattan Project, producing the first nuclear weapons and — following the atomic bombings of Hiroshima and Nagasaki — leading to the unconditional surrender of Imperial Japan and the conclusion of World War II.

Leo Szilárd’s Role

Hungarian physici…