Harry S. Truman

In 1945 Harry S. Truman assumed the presidency after President Roosevelt died while in office. Due to the extreme secrecy surrounding the Manhattan Project, Truman had no previous knowledge of the atomic bomb. He was suddenly confronted with the awesome decision to use "a weapon that would not only revolutionize war but could alter the course of history and civilization." Truman set up a committee of top scientists and advisers "to study with great care the implications the new weapon might have for us."

Truman fully realized that the bomb would inflict unimaginable causalities on the Japanese population, but the invasion of Japan with conventional forces would be far more costly — potentially hundreds of thousands of American and Japanese lives would be lost. Truman’s committee recommended the bomb be used against Japan without a specific warning, but the...