When the time comes that someone in charge of atomic bombs thinks the only way to solve their nations problems, (really their personal problems) is to explode one over some other persons territory it will trigger a massive reaction from every other bomb possessing nation. The first retaliation in kind will quickly precipitate another retaliation in response, but as the first attacker knows the retaliation will be as massive as can be mounted against them, they will begin their assault with as potent a strike as they can muster. The only limitation will be to maintain a credible belief that they have more weapons instantly available. The suspicion of that supply by others, it will be hoped, will be sufficient to deter them from attacking these first users. That hope of not being attacked in return will probably prove forlorn, because no one will trust someone who has suddenly used their weapons, and might have only a few more. So in their own self-defense the other nations will risk a few hits from the depleted stockpile rather than wait for this obviously crazy politico to rearm. It will therefore be far more likely that the this initiator of an atomic war will be instantly attacked rather than for any atomic bomb possessing nation who thinks they might be attacked to resort to diplomacy.
In a world filled with reasonable self-interested and self preserving individuals and nations it is folly to resort to such weapons, no mater what, because it would assure the destruction of their personal self and the nation which they lived within. No sane leader would attempt a war unless it was vital to the survival of his nation, with conditions being so horrendous that if he didn’t attack their nation would surly be destroyed. It is essential to prevent countries from entering into conflicts where they are pushing their competitors into these survive or die situations.
Some people are so identified with their personal beliefs that they would rather die than compromise with someone with some other beliefs. When people with this temperament come to loggerheads it is impossible to reconcile their differences, without physical separation and these conflicts are only in the realm of ideas. However, when it comes to lack of resources for basic survival, such as water and food, then leaders, no matter how wise cannot prevent the suffering and death that Mother Nature demands.
One angry bomb exploding means the nasty bits of Doomsday are very near.