Dear friends,
Several of you have had simply brilliant answers to the original question above--particularly "HiLux"--and I want to thank these for your thoughtful input and helpful answers to the same question that I was having when I did my own search on this question.
I think that part of our problem is that we soon forget the small details of history, and are so easily swayed by modern rhetoric--that so often glosses over the main points, to distract us with irrelevant questions, such as whether the deaths were due to nuclear destruction, or whether they were due to ordinary bombing, regardless of how many were killed, or regardless of what they had done to provoke the invasion in the first place. The women who re-write and teach us history in our universities have certainly pulled the wool over our eyes and distracted us greatly with these irrelevant aspects of war; hundreds of thousands of innocent Chinese are slaughtered for the sake of expanding the Japanese empire, and yet these simple-minded teachers of the blind are more concerned about the children who died in Hiroshima.
(Would that the Japanese had bombed Berkeley, California, instead of Pearl Harbor! We would have had fewer of these teachers around today, and perhaps a little better education about what really happened during the war.)
What a good point: casualties among the invading forces were altogether avoided by choosing to drop the A-bomb from above. It is interesting how willing some people are to excuse any potential deaths among the Allied forces, and even the 100,000 British and American P.O.W.s that would have died in an atomic bombing of Tokyo, but yet refuse to accept the casualties in Hiroshima and Nagasaki, of the enemy himself.
How good it is to be reminded of the facts, so that those of us with rational minds can appreciate what finally happened.
I lived in Japan myself, for five years, in the 1990s, and understand that their respect for authority is infinitely greater than ours in the West--although I must confess, it had seemed logical to me also, at first, to have dropped the bomb on Tokyo, instead; I am reminded by your comments that it was a much more efficient method to have the emperor surrender--so that all the rest of the nation would respect and voluntarily obey his decision--than it would have been for the Allies to kill him, and leave the rest of Japan in perpetual chaos, subject only to their stubborn principle of "never surrendering."
In fact, that answers yet another question that I would have posed myself: why did the Allies not kill the emperor, once he was captured? The answer then, (at least, in part) must be so that they could easily control all the movements of the Japanese by simply directing the emperor and his remarks, from then on.
Thanks again for all the answers.