This question haunted President Truman about dropping the atomic bombs on Hiroshima and Nagasaki. Had he not done so to finally end World War II in the Pacific, that war could have drawn on and on for many more years, killing many more thousands, even millions of young people on both sides, and we might not have been victorious. The Japanese weren’t going to surrender any other way. We might still be fighting them today if Truman hadn’t ended it once and for all.
As horrific as the outcome was for the populations of those cities, not having done so could have been much more horrific in the long run, for everyone concerned. Sometimes, we find ourselves in a corner where the only choices we have are terrible choices, and all we can do is choose the least terrible of them all.
That said, today’s nuclear technology could very well wipe out the entire human race, and I don’t think any power on earth is willing to do that when it comes right down to it, as it would mean their own annihilation, as well. Some put on blustery shows to frighten and intimidate their enemies, but if push came to shove, I doubt anyone would really go through with it.
I could be wrong, and if proven so, it won’t matter to any of us, anymore.