The decision to use the atomic bomb could not be made by committee. Only one man, President Truman, could ultimately make the decision. Truman knew that his was a grave and awesome responsibility. At the Potsdam Conference he issued an ultimatum that demanded Japan surrender or face total destruction. The ultimatum did not reveal the true nature of the nuclear weapons possessed by the United States. The Potsdam ultimatum was the last hope of avoiding the use of the atomic bomb.

American military commanders were planning to invade the southern Japanese island of Kyushu on November 1, 1945. Estimates for the loss of American life in these battles ranged from 250,000 to 500,000 and higher. The Japanese casualties were expected to be much higher. Those in favor of using the bomb hoped that the destruction of cities in the Japanese homeland would provide a shocking...