This post has been updated.

President Trump’s diplomatic style is one that probably wouldn’t work in any other Western country. He’s constantly throwing his weight around on the world stage, musing about breaking up alliances, demanding huge concessions, and claiming to have won big without evidence. The reason Trump’s method works — or, at least, that it hasn’t yet led to a diplomatic crisis — is because he runs the West’s most influential and powerful country.

Foreign leaders have adopted a variety of strategies for dealing with that, generally involving flattery and shrugging off Trump’s impractical and often counterfactual ideas. But Denmark and Greenland’s leaders this weekend didn’t do that; they instead said what they really thought of a Trump plan, and the result is the kind of diplomatic row we all knew might happen one day.

Faced with Trump’s imperial idea to purchase the world’s largest island, Danish Prime Minister Mette Frederiksen responded with the kind of disbelief world leaders have been loath to express publicly about Trump.

“Greenland is not for sale,” she said, adding: “I strongly hope that this is not meant seriously.”

She added that the whole thing was “an absurd discussion” and compared it to a “joke.” “Thankfully, the time where you buy and sell other countries and populations is over,” she said. “Let’s leave it there."

In the same interview, Frederiksen was quick to emphasize that the United States is “our most important ally,” but apparently the damage was done.

Trump made clear Wednesday that he canceled his trip to Denmark not just because Greenland isn’t for sale but also because he felt as insulted by Frederiksen’s response as she was by his overture.

He said her statement “was nasty” — invoking a word he has repeatedly used to describe political women he disagrees with. “It was not a nice way of doing it,” he said. “She could have just said, ‘No, we’d rather not do it.’ ” He added: “They can’t say, ‘How absurd.’ ”

Frederiksen could never have actually played along with Trump on this. He made it a political no-brainer: She could either entertain the idea and look like she wasn’t standing up for her country and the country of Greenland, which is part of the Kingdom of Denmark, or reject it flatly and project strength in the face of a superpower that thinks it can just buy its territory. She took the latter approach, erring on the side of strength rather than diplomacy.

And that’s unusual. Even as Trump has toyed with breaking up NATO, for instance, and claimed massive concessions from member countries (even though there’s no evidence of this), leaders have put a good face on it. After Trump said the NATO members had met his demand to increase their funding of the alliance, French President Emmanuel Macron said matter-of-factly that this wasn’t part of any agreement, but he didn’t belabor the point.

Even as Trump has launched a massive trade war with China that threatens both the U.S. and Chinese economies, Chinese President Xi Jinping has maintained a cordial relationship with Trump, preferring not to add personal insults to an already-volatile mixture.

“The Chinese know that Trump is unpredictable and mercurial, and so they will certainly try not to attack him personally — and they haven’t,” Ming Wan, a professor at George Mason University recently told the Atlantic. “The Chinese are obviously mad, but the response has been less pointed and singularly more measured.”

Trump’s relationship with German Chancellor Angela Merkel has been somewhat rocky, owing in large part to Trump’s desire to point to her country as an example of what happens with too much immigration. But when Trump floated a bilateral trade deal between the United States and Germany during their meeting in 2017 — even though the European Union expressly forbids such things — Merkel chose her words carefully. Witness this amazing anecdote from the New York Times:

Rather than exposing Mr. Trump’s ignorance, Ms. Merkel said the United States could, of course, negotiate a bilateral agreement, but that it would have to be with Germany and the other 27 members of the union because Brussels conducted such negotiations on behalf of its members.
“So it could be bilateral?” Mr. Trump asked Ms. Merkel, according to several people in the room. The chancellor nodded.
“That’s great,” Mr. Trump replied before turning to his commerce secretary, Wilbur Ross, and telling him, “Wilbur, we’ll negotiate a bilateral trade deal with Europe.”

Perhaps the best analog for what we’re seeing between Trump and Denmark is when then-British prime minister Theresa May rebuked Trump for promoting anti-Muslim videos that originated with a fringe British group. Trump’s response was swift:

May, like Frederiksen, had little choice. Opposition to Trump’s impending visit was growing in her country, and she needed to respond with more than just platitudes. She and Trump, of course, ironed things out over time. And similarly, on Wednesday, Frederiksen sought to downplay the situation as being far short of a “diplomatic crisis.” It will be interesting to see how she handles it moving forward, though, if Trump continues to push an idea that her country and Greenland both view as insulting.

Whatever the end result, the flap has provided a rare instance in which a world leader said exactly what they thought about Trump and his ideas. We shouldn’t expect that to be repeated too often.