Basically what the title says. I hate that humanity actually used nukes in war, but when trying to find another alternative that would've led to less casualties, I can't find any. Invasion of Japan was out of the question and would've lead to countless more deaths. Japan had this "victory or death" thing going on so they would fight to the last man. Also why didn't the US surrender to avoid dropping nukes? Would this lead to more war and conflicts down the line? I know that Japan also did horrible war crimes during WW2, would those have continued if it weren't for their surrender? What about driving Japan out of their conquered lands on the asian mainlands and then get to a peace treaty?

Anyone with more knowledge of how war politics work that can answer this?