The thing civilians never see are the classified intelligence reports. The ones for Japan were recently declassified and they showed Japan had withheld its military against the US in the Pacific islands. They were holding their best for the inevitable homeland invasion. They were extremely well prepared. We were facing an Army far larger than our own, that was dug in (even with underground air bases) and ready to fight to the last man. We were facing at least 1 million dead US soldiers, minimum. The bomb was the only answer.
Would appreciate a reference that Japan would have been able to field an Army larger, much less far larger, than our own against Operation Downfall.
The information I've seen indicates we'd outnumber them about 3:1.