learned that two German chemists had split the uranium atom. Enrico Fermi, an Italian physicist who lived in the United States, proposed that a chain-reaction splitting of uranium atoms could release enormous quantities of energy. 

In 1939 Einstein wrote to President Franklin D. Roosevelt warning him that this scientific knowledge could lead to Germany’s developing an atomic bomb. He suggested that the United States prepare for its own atomic bomb research. Out of this effort came the Manhattan Project, in which the first two atomic bombs were developed in 1945. Einstein died in Princeton, NJ, on April 18, 1955.