Their warning eventually resulted in the Manhattan Project.

Szilard worked with Albert Einstein, whose celebrity gave him access to the president, to produce a letter informing Roosevelt of the situation. Although WWII had not yet started, Germany was clearly a threat, and if the Germans had a monopoly on the atomic bomb, it could be deployed against anyone, including the United States, without warning. He feared that Germany was trying to build an atomic bomb, while the United States was sitting idle.