The Japanese had already demonstrated at Okinawa that they were willing to sacrifce civilians by the thousands for no reason whatsoever than to delay the Americans for a few days. They were already training and indoctrinating their entire population for mass resistance. A naval blockade or conventional bombardment would have killed millions, by starvation or fire, before the island finallly fell. The leadership was willing to hold on to the last, not for religious reasons, but to save their own hides from war crimes trials and from the vengeance of the peoples they conquered.

Relatively intact Japanese armies were still scattered all over Asia, without materiel support from the island, or transport, they either would have gone on a rampage, or the local populations would have slaughtered them when their supplies ran out. And as an industrial country, even without material from the outside, they would have still been able to mount a resistance that would have inflicted hundreds of thousands of casualties on an invader, and would have sacrificed tens of millions of their own. And they still could grow enough food for their armies, if not for their people. and there was always fuel for the kamikazes.

American conventional bombing raids were already producing casualties far greater than our nuclear weapons did, it was only the abrupt shock of these bombs that precipitated their surrender. And we only had two. It would have been a year before any more were ready.

In the crazy calculus of war, the nuclear weapons dropped on Hiroshima and Nagasaki probably saved tens of millions of Japanese lives, and perhaps as many as a million Americans dead and wounded. Ironically, in terms of total suffering and lives, I believe it was probably one of the most humane things this country has ever done, although I doubt we realized it at the time.

Thee was just no other way.