1) Curtis LeMay, generally seen as the hardest of hard-liners, strenuously opposed Truman's decision to use the atomic bombs on both Hiroshima and Nagasaki, believing as he did, that use of conventional bombing would be effective and would achieve the desired results in an appropriate period of time, and without the need for a land invasion with its undeniable toll in U.S. casualties, I can't say what his opinion was while the war was actually in progress, but he wrote 20 years later in Mission With LeMay, while describing the firebomb offensive against the Japanese cities, starting with Tokyo (March 9/10, 1945) was that it might (emphasis on the "might") be possible to burn them out of the war.
2) The decision to bomb Nagasaki was unnecessary because the Japanese were preparing to accept unconditional surrender and Truman was too hasty in his use of the second bomb...
I don't know anything about that.
3) The decisions to use the bomb on largely civilian populations, rather than on military targets, were grievous, problematic and unacceptable under international law.
I'm not aware that it was grievous, problematic and unacceptable under international law, at least at the time. Certainly no more so than burning a city to the ground with conventional incendiary bombs (Tokyo, Dresden, Hamburg, et. al.).
It's my understanding that Hiroshima and Nagasaki were generally spared conventional bombing because we wanted some "intact" cities for a better test of the actual effectiveness of the bombs.
Them's my thoughts.
Thanks for troubling to comment on the issues I raised. There were numerous reports during the the past 50 years that LeMay had strongly opposed use of the atomic bomb on Japan, and I have never once heard that Le May, or his acolytes, ever denied their veracity. The day before (August 10, 1945) the bombing of Nagasaki it was widely reported in the North American press that the Japanese had told a Soviet envoy that Japan was ready to surrender. To be sure, the firebombing of Tokyo, Dresden and Hamburg were every bit as open to the same objections: deliberately 'terrorizing' and incinerating utterly defenceless civilian populations is unacceptable, as unacceptable, say, as the Nazi death camps. I realize that what I have said here proves nothing. It merely resurrects perennial considerations that deserve an airing whenever the subject arises. One of the most eloquent essays I've ever read on the subject of the deliberate extinction of large civilian populations was written about 30 years ago, by the Welsh actor, Richard Burton, who confined his remarks to Churchill's unilateral decision to firebomb Dresden, a purely non-military target of great architectural beauty.