Historians and others will be debating the necessity of the atomic bombings until the end of time.
I can't really judge the military details, but I did find it interesting that Eisenhower didn't think the bombings were necessary.
This interesting fact also occurred to me. The definition of "weapons of mass destruction" usually has three elements: chemical, biological and nuclear. Three of the major belligerents in WW2 were working on them: the US specialized on nuclear, the Germans on chemical (they had discovered nerve gases in the 1930s) and the Japanese on biological (conducting some well-known and horrific tests).
But of the three, only the US actually used its weapon in war; the other two intentionally held back.
Agreed that the debate will continue forever.
Lets take a look at the military viewpoint for a minute. Most if not all the commanders deemed the war was won by the time the atomic bombs were dropped n Aug 1945(Man that is 70 years ago!). However war records speak differently. From Wikipedia
https://en.wikipedia.org/wiki/Pacific_War#Okinawa The US had 75K casualties, the Japanese had 94% death fighting "to the last man". And this was after an intense aerial bombing campaign. So the mainland invasion scheduled for Oct-Nov 1945, would likely have involved similar casualties.
Secondly and perhaps more importantly, bombing
never has won a war/battle. Ground troops were a necessity to final victory. Look at the air war over Britain/Germany/Japan that failed to bring the conflict to conclusion. An invasion would have been required.
Thirdly many historians military and civilian have noted that the Japanese did not have the ability to wage further war from lack of resources. There is truth to that statement, but that includes an air/sea battle worthiness, not a defensive land operation.
Fourthly the Japanese military conducted operations from the Bushido code, namely
never surrender because that is a cowards way out. Look at how the POW's from the early battles were treated by the Japanese, those individuals were below life as they had not fought and died.
A land invasion would have been required and resulted in large numbers of Allied casualties. Dropping atomic weapons whether in a questionable morale aspect was necessary to stop the war earlier.