“He’s like Heath Ledger’s Joker—but without the operational excellence.” That was the grim after-action assessment of one senior G7 official with whom I spoke in the shocked aftermath of President Donald Trump’s savage post-summit tweets.

To the very last minute, the Charlevoix summit seemed business-no-worse-than-usual. Trump had arrived at the summit in a credible semblance of a jolly mood. He joked about where he would site the condos if he redeveloped the hosting hotel. He assured the other heads of governments not to mind the false reports in the media. We’re all still friends, he said. We’re going to make a deal.

The United States still being the United States, the deal was made on America-friendly terms. Language praising the “rules-based international order” was struck to appease Trump. His aides explained: The guy campaigned against a system his voters think is broken. He can’t sign a document praising that system.

During the sessions, he was visibly swayed by the appeal from the other democratic leaders: The senior G7 official characterized the mood of accord that seemed to be taking hold during the summit hours: What are we fighting over? We’ve built something that has delivered more prosperity for more people than the world has ever seen. Can’t we keep it working? In the moment, Trump seemed to share the mood.

Whether or not the president’s demands made any sense even from the most parochial American point of view, his demands were to a considerable extent accommodated. Trump had issued orders, sent his people out to war, and won victories for his idiosyncratic approach to foreign affairs. As late as 3:30 on Saturday afternoon, all the conferees thought that the facade of Western unity had survived another day, another summit.

Not even the president’s testy Saturday morning attack-CNN press conference shook the assembly. On his way to the podium, he winked and joked—a performer about to mount a show. “Trump’s gonna Trump,” an official from another G7 government quipped to the official to whom I spoke.

Like some nightmare family Thanksgiving from which the most difficult relative departs first, everybody breathed easier when the president at last left. Perhaps after all, it was sort of a success?

Then, something happened. From Air Force One, the president emitted a vituperative series of tweets aimed at his Canadian counterpart. What had triggered him? Had he belatedly seen that photograph of Angela Merkel looming over him? As many have said: Trump thinks in images, not ideas. Who could ever know? Trump probably does not know himself.

Ominously too: Once Trump started tweeting out abuse, the snakepit of hissing, warring aides around the president suddenly competed to amplify and deepen the quarrel. At 6:56 pm, National-Security Adviser John Bolton tweeted out his own version of the offending image of Merkel topping Trump—only with a caption reinterpreting the scene as proof of Trump’s strength and defiance. “Just another #G7 where other countries expect America will always be their bank. The President made it clear today. No more.” On pro-Trump Twitter—and then on pro-Trump TV and radio—that would almost instantly consolidate the new message line. The allies had tried to muscle the strong-willed president. But he had held firm.

Of course, all this blatantly contradicts yesterday’s message line. Remember, Trump holds authority to impose tariffs on steel and aluminum because—and only because—of a Kennedy-era special exemption to normal trade law for national-security purposes. Trump has signed documents attesting that he imposed tariffs to protect vital defense interests of the United States. Now he has changed his story. The tariffs on steel and aluminum from Germany, the U.K., Mexico, and all the others were not a national-security measure, but a retaliation for Canada’s restrictions on dairy imports. Whatever you think of Canada’s milk protectionism (and few Canadians who don’t directly profit from it will defend it), it is not a threat to U.S. national security.

But does Trump notice or care that he has given himself the lie? Surely not. Trump is recovering from two weeks of criticism that he went soft on the Chinese tech giant ZTE. A bipartisan group of 27 U.S. senators signed a letter criticizing him, and even Fox News chimed in. The president’s opponents suggested that his decision had been swayed by a state-owned Chinese company’s $500 million investment in an Indonesian project that had licensed Trump’s name.

Vexed by the criticism, Trump struck back at the readiest targets: America’s closest friends and allies. Rule-of-law democracies cannot deliver the emoluments Trump collects from more authoritarian regimes. They cannot expedite Ivanka Trump’s trademarks to gain favor. They don’t book their national-day celebrations in Washington’s Trump International Hotel.

Trump’s revenge-tweets from Air Force One back at his Canadian hosts probably did not lose him any friends in Canada, for the basic arithmetic reasons that a few alt-right YouTubers aside, he had no friends in Canada left to lose. Trump’s attacks on Trudeau will only boost the prime minister’s popularity. But this is more than a personal story. Trump is day by day abdicating U.S. leadership. “He is testing to the breaking point relationships that there was never any reason to test in the first place,” said the G7 official, resignedly. (The official spoke on condition of anonymity, due to the confidential nature of the discussions.)

The governments of the G7 are America’s closest partners and allies: “None of us has the luxury of being pissed off,” the official said. But from Canada, Trump has arrived in Singapore to meet North Korea’s Kim Jung Un. It is a good guess that he will show himself much more respectful and conciliatory to this dictatorial adversary than to America’s democratic friends—by now, that’s a familiar pattern of Trump behavior.

Trump is locked into a cycle in his top-level diplomacy: bully-cringe-bully-cringe. He bullies traditional friends and allies; he cringes to adversaries, dictators, and potential funding sources for Trump enterprises. Bullying the G7 was the weekend’s story; cringing to North Korea—and behind it, China—will be the story of the week ahead.