Here's the thing. At the time, it was just another weapon in a war that saw all sorts of weapons used by all sides... Horror on a level most of us couldn't understand today.
Later on, when Nukes became an existential threat to the species, people asked why we used them, but at the time, there was no question. We were at war, they started it.
It's a wonderful case of applying modern values to people in the past who would have looked at you funny.
It did not have to be a question of whether we used them or not
Did we have to choose targets where 150,000 civilians were killed?
Could a non lethal “demonstration” have yielded the same results?
Drop one in a low populated or strictly military area and let the Japanese evaluate the results. Then tell them we have dozens just like it and would target Tokyo next
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As a person that was alive and aware at the time the two bombs were dropped on Japan, I can tell you that you're full of crap. History proves that made the right decision. The invasion of Okinawa proved that the invasion of the four main islands of Japan would be a blood bath on both sides. I suggest you read about Operation Olympic and Operation Coronet and the overall plan Operation Downfall.
Without the use the two "Atomic Bombs", The U.S. military, expecting resistance by a “fanatically hostile population,” made preparations for between 1.7 and 4 million casualties with up to 800,000 dead. Between 5 and 10 million Japanese deaths were projected. By dropping the bombs yes up to two hundred twenty five thousand died as compared to estimates of a full fledged invasion.