President Trump speaks with reporters as he arrives at a New Year's Eve gala in Florida on Dec. 31. (Evan Vucci/AP)

Six hundred and eighteen days ago, Donald Trump said he would no longer tweet if he were elected to the White House. “Don’t worry, I’ll give it up after I’m president,” he said, adding that it was “not presidential.”

On Tuesday, Trump rang in the second year of his presidency with a fusillade of unpresidential tweets, including arguably his most provocative about North Korea. Trump, who infamously alluded to the size of his genitalia at a 2016 debate, assured Kim Jong Un that his nuclear button is “a much bigger & more powerful one” than Kim's.

Where to begin?

Trump's penchant for inflicting controversy upon the U.S. political process has been a feature of his campaign and presidency. It shows no signs of abating, and, in fact, he seems in many ways to be feeling the need to up the ante to keep the nation's attention focused on him.

But tweets about using nuclear weapons are clearly in another category. These demonstrate that Trump's provocative streak isn't limited to fomenting culture wars; it could play a role in fomenting actual wars — even a nuclear one. This is deadly serious stuff, in the truest sense. Trump has talked about “fire and fury” raining down on North Korea and “totally destroying” that country. He has clearly embraced the second half of President Theodore Roosevelt's “speak softly and carry a big stick” mantra — although clearly not the first.

And yet Trump's provocations when it comes to North Korea fit a pattern just like the rest of his tweeting and controversy-stoking. Just as Trump seems to consider his 2016 election win a complete vindication of his approach to domestic politics, he seems to view what is largely regarded as a successful first year on the foreign policy front as vindication of his increasingly audacious approach to North Korea.

Even some of Trump's most vocal critics have acknowledged that the United States made significant foreign policy progress in his first year. Gains against the Islamic State have accelerated to the point where the terrorist group has been pushed out of Iraq, and its self-declared caliphate appears to have collapsed. Trump's decision to strike Syria in response to its use of chemical weapons on its people registered as one of his most popular decisions. And the unification of the U.N. Security Council in imposing new sanctions on North Korea — the unanimous vote included regular holdouts China and Russia — was clearly a strong moment for the Trump administration and Ambassador Nikki Haley.

Exactly how much credit the administration deserves for any of these things is up for debate, but it's not difficult to see why Trump views his foreign policy record as a series of wins — just as he saw his approach to domestic politics as a series of wins during the 2016 campaign. Trump tends to view wins as wins and losses as symptoms of an unfair process or nefarious actors working against him. But on foreign policy, he doesn't have to stretch too far to paint a strong picture of his tenure.

But the big question with Trump's foreign policy has never been about whether he and his advisers could manage ongoing conflicts in the Middle East or sanctions against rogue regimes; it has been about whether his gunslinging approach could lead to disaster. In foreign policy and diplomacy, after all, you need to mess up only once before it becomes a defining moment of your presidency and the nation's history. And polls show that Americans have little trust in Trump to handle the situation in North Korea.

Former CIA director David Petraeus summed it up well a few months ago while talking about Trump's “madman theory” approach to foreign policy:

There is some merit to this. You can argue perhaps there is some merit to it in international relations, although it obviously can go too far. . . . There may, again, be some merit into the madman theory until you get in a crisis. But you do not want the other side thinking you are irrational in a crisis. You do not want the other side thinking that you might be sufficiently irrational to conduct a first strike or to do something, you know, so-called “unthinkable.”

Trump has had enough foreign policy wins that he probably thinks his madman approach is working. But a central feature of the madman approach is that it appears to work well right up until the moment it backfires and turns to tragedy. That's the very dangerous game Trump is playing with these kinds of tweets, and it seems to be giving even those around him an unhealthy — but extremely understandable — amount of heartburn.