There are a lot of articles circulating on this subject, I advise you all to read as many of them as you can. Here's an interesting one: http://www.salon.com/2015/08/05/ame...ist_history_that_haunts_the_good_war_partner/
On August 9, 1945, President Harry Truman delivered a radio address from the White House. The world will note, he said, that the first atomic bomb was dropped on Hiroshima, a military base. That was because we wished in this first attack to avoid, insofar as possible, the killing of civilians. He did not mention that a second atomic bomb had already been dropped on Nagasaki.
Truman understood, of course, that if Hiroshima was a military base, then so was Seattle; that the vast majority of its residents were civilians; and that perhaps 100,000 of them had already been killed. Indeed, he knew that Hiroshima was chosen not for its military significance but because it was one of only a handful of Japanese cities that had not already been firebombed and largely obliterated by American air power. U.S. officials, in fact, were intent on using the first atomic bombs to create maximum terror and destruction. They also wanted to measure their new weapons power and so selected the virgin targets of Hiroshima and Nagasaki. In July 1945, Secretary of War Henry Stimson informed Truman of his fear that, given all the firebombing of Japanese cities, there might not be a target left on which the atomic bomb could show its strength to the fullest. According to Stimsons diary, Truman laughed and said he understood.