The Nuking of Japan

[Reforged]

There is a reason why those nukes are still to this day the only nukes ever launched against a country during a war. It's because we realised how much of a mistake it was to use them. Nukes cannot be controlled; they will destroy much more than is intended, and they leave behind deadly radiation that spreads, killing more and more people who weren't even initial targets.

Don't worry, I'm sure they're working on cleaner methods of mass destruction. The reason no-one uses nukes to vie for supremacy is fear. If there wasn't the fear of retaliation with a similar type of weapon, if there was but one nation with weapons of this kind they would use them to dominate their neighbours with little hesitation.
It is not for such environmentally conscientious reasons as you suggest. Time and again it has been demonstrated that power is more important to a nation than its people or even its planet.
It is fear of retaliation that staves off this outcome, not environmental prudence.