My father survived two amphibious landings on Japanese held islands in the Pacific. When the war ended, he was recovering from malaria and knew he would have been part of an amphibious landing on mainland Japan had the war not ended.
From what he saw first hand of the fighting in the Pacific, there was absolutely no doubt in his mind that dropping of the atomic bombs was the right thing to do.
I would also point out that those who question the morality of the atomic bomb, need to look at what alternatives would have been used. The Army Air Corp had already been firebombing major cities leading to huge civilian casualties. Further, the naval blockade of Japan had produced a food crisis in the County.
At the time of year that the atomic bombs were dropped, the weather in Japan was still reasonable. If the war had gone on the homeless exposed to the elements from homes destroyed by fire bombing and the starvation would have also produced mass civilian casualties.
Using any means to end the war as quickly as possible, was the moral thing to do.
This is the money quote.
Once civilians are accepted as a legitimate target, any argument of how their demise is brought about is a waste of time.