And when you turn on the evening news
Mass confusion is the only thing you see
Well there's no question that we need a new direction
Cause we all could use some peace and harmony
--Love Will Save the Day,
You gotta be bad, you gotta be bold
You gotta be wiser, you gotta be hard
You gotta be tough, you gotta be stronger
You gotta be cool, you gotta be calm
You gotta stay together
--Ya Gotta Be,
There is a choice. One may make a realistic threat assessment prior to taking a discretionary action (Like the Afghan and Iraqi Wars), or one may leap upon the braggadocio of an adversary who may be acting out of a feeling a threat and call it a legitimate casus belli.
The rational player should realize, if you have an insane adversary, to even reply is an insane act.
In the case of NoKo's Kim Jong-Un, a little sabre-rattling is most probably an adequate response. A display of force, like deploying an aircraft carrier group off of his shores, would allow Kim to save face. He may spin it to his people as he wishes. ("You see how important I am? Just look at their response!")
Instead of President George Bush's schoolyard bully reply ("Bring it on!") to Saddam Hussein, the President may instead choose to ignore the prod of inflammatory rhetoric, not chomping at the bit after every word. Like mothers used to advise when dealing with bullies, "Pay him no never-mind!", or "Like water off a duck's back". "Do not go down to his level." Bullies usually act from fear.
The President could act as a hostage negotiator with Kim. If we take his threat as viable, Mr. Kim is taking the NoKo people and the world hostage. It is important to note, the hostage negotiator cares as much for the dignity and survival of the hostage taker as he does for that of the hostages.
When dealing with various threats, politics is often hostage negotiation at an international level.
Bush disallowed Saddam his dignity; there was no way out for either man. In hostage negotiations one never corners the hostage taker. On an international level, especially when dealing with an autocrat -- and especially in the orient -- the leader should be allowed to save his respect. This all part of the game of realpolitik.
President Trump betrays his campaign platform of non-interference when he engages in tit-for-tat inflammatory rhetoric. He should be curtailed from his trash talk; following in the footsteps of GWB is not winning (as Charley Sheen might say.)
At the end of the day, Kim likes his Emmenthaler, American Basketball and Dennis Rodman. He should be satisfied with the opportunity to wallow in a bit of puffery.