It's impossible for us to understand the situation in context due to the passage of time- our distance from it clouds and distorts the entire event. It seems at the time there was no other realistically viable option, and I doubt the decision to drop the A-bomb was made casually.
That doesn't mean I'm in favor of what was done, what I mean is that sometimes the only choices you have are bad ones.
It's chilling to see how the city was virtually wiped clean off the map, especially when you realize that the bomb they dropped was a very, very tiny one compared to the ones that would be used today. A full-sized nuke today would pretty much remove Japan from the world map down to a couple of hundred feet below sea level. It's hard to grasp the effect a current nuke would have; it's just not easy for the mind to scale to that level of destruction.
When I worked at Hanford, one of the nukies there remarked that the bomb used on Hiroshima was so tiny, "they wouldn't even waste their time building one that small these days".
He said it's impossible to visualize the destruction a current bomb would cause, but that to get an idea of it you could go to the top of a 50-story building, turn in a complete circle and imagine that everything you see -
every single thing- is completely gone.
That was kind of sobering.
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Full Disclosure: Yes, a long time ago I worked at Hanford ("Westinghouse-Hanford" back then) for Battele and Rockwell and a few other groups. I'm well-acquainted with the nukies, the 'glow-to guys' (ha ha) and SWP, SNM, and all that other junk. I've also done work for other nuke farms like Sandia, Lawrence Livermore Labs, INEL, Rocky Flats and GE Vallecitos. I've spent more time in poop-suits than I care to remember. I was superficially contaminated three times at Hanford (doh!) so I don't have very fond memories of it, to be honest.