President Trump has agreed to meet North Korean leader Kim Jong Un, a decision that reportedly surprised U.S. diplomats and set about a preparation panic. Suddenly, we have an unwieldy and bellicose U.S. president set to meet with an unwieldy and bellicose foreign dictator — to discuss nuclear weapons, no less.

Nobody knows quite what to expect. But here's what we can say about Trump's brand of diplomacy, based upon evidence.

1. Clashes have proved Trump to be just as unsteady internationally as domestically

With Trump, the question has long been how much of his controversial and wild behavior is deliberate and how much is contrived — even strategic. On the domestic level, we have seen Trump's inability or unwillingness to tone down his behavior early and often. It's well-acknowledged that he will never be traditionally presidential; it's just not in him.

On the international level, we have less of a paper trail to study. But the evidence suggests Trump isn't much steadier in his dealings with foreign leaders than he is with congressional ones.

Early in his presidency, The Washington Post obtained transcripts of Trump's conversations with the leaders of Australia and Mexico. Trump's call with Australian Prime Minister Malcolm Turnbull was particularly unchained, with Trump berating him over Australia's deal to send refugees to the United States. Trump appeared to have almost no knowledge of the agreement before speaking with Turnbull, and by the end he hung up on him.

Here's a quick sampling:

TURNBULL: But can I say to you, there is nothing more important in business or politics than a deal is a deal. Look, you and I have a lot of mutual friends.
TRUMP: Look, I do not know how you got them to sign a deal like this, but that is how they lost the election. They said I had no way to 270 and I got 306. That is why they lost the election, because of stupid deals like this. You have brokered many a stupid deal in business and I respect you, but I guarantee that you broke many a stupid deal. This is a stupid deal. This deal will make me look terrible.
TURNBULL: Mr. President, I think this will make you look like a man who stands by the commitments of the United States. It shows that you are a committed —
TRUMP: Okay, this shows me to be a dope. I am not like this but, if I have to do it, I will do it but I do not like this at all. I will be honest with you. Not even a little bit. I think it is ridiculous and Obama should have never signed it.

An account of Trump's relationship with Mexican President Enrique Peña Nieto, meanwhile, could fill a book. Trump met with Nieto during the 2016 campaign, but the meeting led the two sides to dispute one another's claims over whether they had discussed Trump's pledge to make Mexico pay for his border wall. After a thaw in relations, just two weeks ago, Nieto canceled a visit to the White House after a testy exchange with Trump over (again) the wall.

The last pertinent example is Trump's handling of Russian President Vladimir Putin. Trump has repeatedly cast doubt upon the intelligence community's conclusions about Russian interference in the 2016 election, and when he met Putin, he basically backed down and accepted Putin's denials. “Every time he sees me, he says, 'I didn't do that,' " Trump explained in November. “And I believe — I really believe that when he tells me that, he means it. But he says, 'I didn't do that.' I think he's very insulted by it, if you want to know the truth.”

In other words, Trump is extremely tough with some allies and apparently extremely deferential to the likes of Putin — exactly the opposite of what you would expect from a U.S. president. Given that, it's anybody's guess how he'll handle Kim, and it may not be how the State Department would like him to.

2. Trump has almost no message control

Aaron David Miller, who has negotiated in the Middle East for both Republican and Democratic administrations, put it this way Thursday night:

Basically, the No. 1 rule of summits like this is to know as much as you can about what's coming, do as much prep work as you can, and be studied and consistent in your approach.

None of that describes how Trump has conducted himself as president; he has usually been the antithesis of all that. On issue after issue, whether immigration or guns or that Oval Office meeting with Russian leaders, he has proved he can't stay on script. In fact, he often doesn't seem to bother even studying the script. Trump regularly appears unfamiliar with the policies he's discussing, changes his mind within days or even hours, and makes decisions that haven't been thoroughly vetted.

Given that this whole process started with Trump's apparently impromptu decision to grant Kim a meeting, it doesn't seem likely Trump is planning to bring a more studied and judicious approach to it. And that will give those charged with preparing him for the meeting weeks and weeks of heartburn.

3. Trump's bellicosity may have gotten him to this point

However nontraditional and apparently undisciplined Trump's style is, there is an argument to be made that it's responsible for the progress made on North Korea. I wrote about this earlier in the week, and The Post's Karen DeYoung offers a much more scholarly review on Friday.

Experts credit Trump's “madman” approach and general strategy toward North Korea with moving the needle on United Nations sanctions and for creating a climate for discussions during the recent Winter Olympics in South Korea. Not everyone agrees that a presidential summit is a good idea, but notwithstanding that there have been clear advances.

There is also some thought that perhaps this is simply the style to which Kim responds — and that Trump's changing things now might not be the best call.

But that's the most optimistic take on how all this might turn out. We're now in a much more detailed and delicate portion of this process, and Trump has repeatedly failed to demonstrate a propensity for either details or delicacy.