The 18th of June, 1945, was a momentous day in the war against Japan and in the history of the atomic bomb. Two months before, while posing for a portrait, President Roosevelt had unexpectedly died of a cerebral hemorrhage at his favorite retreat - the "Little White House" in Warm Springs, Georgia. Eighteen days later Hitler committed suicide, ending the war in Europe. It seemed, however, that Japan had no plans to stop fighting.
On that summer day in June, President Truman knew the United States was developing a secret weapon: an atomic bomb. The question was: Should he use it? Debating the issue with his closest advisors, Truman was worried. If American forces invaded Japan’s home islands, the human cost would be extraordinary. As he listened to the discussion, Truman remembered the battle of Okinawa.
THE PRESIDENT expressed the view that it [an invasion] was practically creating another
Okinawa [where thousands of Americans and Japanese had died] closer to Japan to which the Chiefs of Staff [Truman’s military advisors] agreed.
Truman believed the cost of American lives would be too great. On June 18th, the president decided to force Japan’s surrender by use of other means. Instead of invading Japan, America would use its new - as yet untested - weapon.