Einstein–Szilárd letter — letter by Leó Szilárd and Albert Einstein to US President Roosevelt in August 1939
This letter prompted Roosevelt to authorize nuclear research, ultimately leading to the Manhattan Project and the first atomic bombs.
Key Facts
- Date signed
- August 2, 1939
- Primary author
- Leó Szilárd
- Signatory
- Albert Einstein
- Recipient
- President Franklin D. Roosevelt
- Co-consultants
- Edward Teller and Eugene Wigner
- Direct outcome
- Initiation of U.S. nuclear weapons program
Location
Cause → Event → Consequence
Physicists Szilárd, Teller, and Wigner feared that Nazi Germany was actively pursuing nuclear fission research and could develop an atomic bomb. They believed the United States government was unaware of this danger and needed to be alerted at the highest level, leading them to draft a letter under Einstein's prestigious name to reach President Roosevelt.
Leó Szilárd authored a letter, signed by Albert Einstein on August 2, 1939, and addressed to President Franklin D. Roosevelt. The letter warned that Germany might be developing atomic bombs using nuclear fission and urged the United States to launch its own nuclear research program, outlining both the scientific possibilities and the geopolitical risks involved.
Roosevelt took action in response to the letter, establishing advisory committees on uranium research. This process eventually led to the full-scale Manhattan Project, during which the United States developed the first nuclear weapons. These bombs were subsequently used against the Japanese cities of Hiroshima and Nagasaki in August 1945, fundamentally reshaping global military and political order.
Political Outcome
Roosevelt authorized nuclear research programs that culminated in the Manhattan Project and the development and use of atomic bombs on Hiroshima and Nagasaki.
No formal U.S. government nuclear weapons research program existed.
The U.S. government began organized nuclear research, leading to the Manhattan Project.