The planning for Operation Downfall expected a minimum of 5 million Japanese civilian deaths. The Japanese plan for defending the home islands, ketsugō sakusen

The planning for Operation Downfall expected a minimum of 5 million Japanese civilian deaths. The Japanese plan for defending the home islands, ketsugō sakusen, involved conscripting the entire population into a militia. The propaganda term was literally "The Glorious Death of One Hundred Million." If you don't think that would've killed more than 250 thousand civilians you're a fool. The target choices, Hiroshima and Nagasaki, are a good topic for debate. There's ample argument to be made that there were better, more militarized targets that would have shaved significant fractions off the ultimate civilian death toll. There is no sane argument, however, that the bombings themselves didn't kill an order of magnitude fewer people than any other method of defeating the Japanese Empire.