One. the bomb was capable of doing the equivalent damage as a full raid by B-29s (and its probably easier to stop single plane raids than massed formations), so the Japanese would not necessarily have been awed. more important, the decision was the war planners of August, 1945 to make, based on their best assessment. monday morning quarterbacking doesn’t add much to understanding the issues. by the way, the option of a demonstration was explored and rejected. so unless Fr. Knox was one of those war planners, his opinion doesn’t carry much weight.
The air war against the Japanese had been ongoing since 1944 with conventional weapons achieving similar effects on similar targets. post war studies make it very clear that the air war – firebombing Japanese cities – was decisive, and that the atomic bombings hastened the end by a couple of months. also clear that without the air war, if the DOWNFALL invasions had gone forward, deaths from all causes would have been in the millions.
Two. Japanese war industry was purposefully decentralized to make it a hard to fully destroy, moreover allied planners did not bomb civilian areas just because they were civilian areas. the mission plans always identified military targets. they happened to be, often enough in civilian built up zones.
an important note repeatedly missed here. the japanese economy, managed and operated by civilians, was totally mobilized for war. it takes hundreds of people not wearing uniforms to maintain one man killing, which the Japanese soldiers had been doing to the Chinese (military and civilian) at the rate of over 200,000 per month for the past eight years. without the support of civilians, this killing machine would not have existed.
so before you wring your hands over Japanese civilians casualties, at least acknowledge their complicity in the mass death the IJA inflicted and the hobson’s choice faced by allied military planners.