Now everyone's asking the question -- has Trump confounded the pundits, has his bombast finally landed a knockout blow, or at the very least stunned his opponent into agreeing a face-to-face meeting?
Kim's retort in North Korean media, telling Trump he is an "old lunatic" and a "dotard," revealed a dangerous flash of his volcanic temper.
Verbal sparring is Trump's go-to move. Few leaders are prepared to step into the ring with him. But Kim did.
The Hermit Kingdom's leader says he is intent on making nuclear weapons and ballistic missiles capable of reaching the United States.
Nothing he has done yet changes that narrative. But this week, after years of ignoring international concerns and starving his own people to feed his weapons program, he held talks
with South Korean officials about halting those programs
So has Trump's hurtful haranguing actually worked?
On North Korea, Trump inherited a mess. Obama's presidency ended just as Kim's ticking time bomb of nuclear readiness became an urgent matter.
North Korea was always likely to be Trump's first big diplomatic test.
We will never know how a President Hillary Clinton might have handled Kim. America took a different path and much of the world has been holding its breath ever since. But maybe now is the time to exhale.
As undiplomatic as Trump is, he appears not only to have gotten Kim's attention, but he might have found a way to slow him down a bit.
That said, it's very hard to tell what goes on underneath Kim's haircut. It's entirely possible that his talks with South Korea are simply Kim playing his old game: acting like he is going to do something in order to buy himself more time, then pushing ahead with his program as normal.
In his own mind, Kim likely considers he has already joined the nuclear bomb-capable club and talks will focus on cementing that as internationally accepted fact.
It wasn't just Kim who paid attention to Trump's approach for dealing with North Korea: China and Russia looked on as the US ramped up joint military exercises with South Korea and Japan.
It angered the hell out of diplomats in Beijing and Moscow, who all claimed Trump was destabilizing the region.
Both capitals still want America's military assets, troops, warships and missile systems out of the region -- though for all their own tempered bellicosity about Trump's damage to diplomacy, it's pretty clear what they really want is less interference in what they consider to be their own back yard.
The past year has been an unnerving one for all concerned. No one really knew when Trump was blowing hot or cold.
Take his own secretary of state, Rex Tillerson, who undertook a mammoth diplomatic haul, flying to Beijing and back in a weekend to pressure China to fully enforce economic sanctions on North Korea.
Barely was Tillerson back in the US when Trump tweeted
that his top diplomat may as well not have bothered going.
Trump has doubled down on this more than once since, saying he doesn't need diplomacy, the military can do the job; that he doesn't need Tillerson because only he makes the decisions.
But Trump has come closest to getting what he wants when he is quietest.
Yes, these talks only came about because of South Korea's gracious invitation to North Korean athletes, allowing them to compete in the Winter Olympics.
The million-dollar question is whether or not Trump did in fact create the conditions for this thaw. The answer to that question will be crucial to whether or not the other players in this diplomatic standoff swing behind the US in the future.
China has never been a willing partner in the US-driven sanctions on Kim.
Russia, meanwhile, has been playing its own angles: inveigling itself as a key partner in the sanctions process while at the same time breaking the sanctions, secretly shipping North Korean coal to South Korea and Japan.
The consequences of denying diplomacy might be coming home to roost for Trump. Both China and Russia -- while complaining about the dangers of the President's actions -- appear to have found ways to navigate his apparent unpredictability.
Kim entering talks is not a success in and of itself. The outcome and what tangible, verifiable change they may produce will matter far more.
Australian Foreign Minister Julie Bishop warns of the possible pit falls. "North Korea has a history of making agreements and then failing to honor them," she said.
And this will all ultimately rely on Trump's ability to swing a coalition behind whatever emerges from these talks. And that will be a far greater test. While looking for allies, he will be dogged by his past insults and the trade war his tariffs on steel and aluminum
are expected to trigger.
Australia's Prime Minister Malcolm Turnbull has already hinted that those tariffs could trigger reactions beyond just business, saying there was no basis for them when balancing trade with overall economic and strategic interests.
Trump could find himself back in the ring with Kim, sparring again using innuendo and insults, with no one holding the towel in his corner.
The world is getting the measure of Trump. And while he no doubt weighs what he sees and adjusts his fire accordingly, his measure of the world seems to be tilting away from him.