On August 10, 1945, Emeror Hirohito announced to the Japanese people in a radio broadcast that their country had agreed to terms of unconditional surrender in World War II. In doing so, the Emperor had agreed to terms that had been offered as an ultimatum to the Japanese government in late July following the Potsdam conference. The ultimatum offered the choice between total and unconditional surrender or total annihilation. In their initial reply, the Japanese did not capitulate completely. On August 6, the Enola Gay (a B-29 bomber) dropped an atomic bomb on the city of Hiroshima. Three days later, as Japan still defied the ultimatum, a second atomic bomb was dropped on Nagasaki. In the face of threats of further such attacks, the Emperor, who had previously rubber-stamped all of the war decisions by his military leaders, stepped up and made the decision to submit unconditional surrender.
There has been much cringing and hand-wringing in recent years over President Truman's decision to employ the atomic bombs, but I think a very strong case, even an inarguable case, can be made in support of the decision. Here is Victor Davis Hanson in a 2005 National Review Online article. "The truth, as we are reminded so often in this present conflict, is that usually in war there are no good alternatives, and leaders must select between a very bad and even worse choice. Hiroshima was the most awful option imaginable, but the other scenarios would have probably turned out even worse."
The whole article can be read here: http://old.nationalreview.com/hanson/hanson200508050714.asp