I am looking at the numbers from operation downfall that Truman and senior members of the administration looked at which had between 500,000 to 1,000,000 lives lost on the US side for a Japan invasion/defeat. 406k US soldiers lost their lives in WW2 so that would have more than tripled the deaths from its current numbers. And as for WWI and British casualties which I mentioned earlier, the British lost around 885k troops during WWI so US would have exceeded that number even on the low end of casualties.
Yeah it would have been a bloody invasion. I'm saying it probably would not have been necessary since Japan was under siege and basically out of food already.
https://en.wikipedia.org/wiki/Operation_Downfall#:~:text=Tru....