While the impeachment process was rumbling forward in Washington on Wednesday, President Trump was grumbling about his fellow leaders in London.

Grumbling — and calling them names — at the close of a summit that should have been a celebration of the 70th anniversary of NATO, the grand alliance formed in the wake of the bloodiest war in history.

Trump called Canada’s prime minister, Justin Trudeau, “two-faced,” and later declared his own remark “funny.” The day before, Trump said French President Emanuel Macron was “very, very nasty.”

But given Trump’s history of intemperate, insulting speech, his words appeared to have little impact on Trudeau, Macron and others attending the summit. It was a sharp contrast with previous meetings, when world leaders were taken aback by Trump’s undiplomatic behavior.

“President Trump has always relished throwing European leaders off balance, antagonizing allies, embracing insurgents and setting off a frantic contest for how best to deal with him,” writes Mark Landler in the New York Times. “Now, as Europe undergoes dizzying political changes of its own, it is throwing Mr. Trump off balance.”

Ironically, one of the few NATO leaders who seems to be a natural Trump ally, British Prime Minister Boris Johnson, did not meet with him on Wednesday. The two leaders appeared to have agreed to keep their distance, since Trump is profoundly unpopular in Britain and Johnson faces a U.K. election next week.

But Trump met cordially on Wednesday with the despotic Turkish president, Recep Tayyip Erdogan.

Macron and other European leaders want NATO to get tough on Turkey over its purchase of surface-to-air missiles from Russia — and its invasion of northern Syria in October (after Trump left the way open by withdrawing U.S. troops and abandoning Kurdish forces fighting ISIS).

Also Wednesday, against the background of a summit to celebrate the unity of the alliance, “Trump convened his own sub-group … limited to only those meeting [NATO’s] defense spending target” of 2% of each nation’s GDP, reports the Associated Press.

In an analysis piece for CNN, Chris Cillizza takes a look at how Donald Trump’s abrasive personality comes so readily to the fore when dealing with ostensible allies:

“Trump has spent his entire life feeling as though he is on the outside looking in at the cool kids, or as he has taken to calling them, ‘the elites,’” Cillizza writes, pointing out that the president has “regularly riffed on his sense of alienation — and how angry it made him.”

Cillizza adds: “This is yet another club — Macron, Trudeau, Johnson — that doesn’t want him as a member. And not only that, but they appear to be in their little club mocking him. It’s everything that Trump hates.”

Even as the president departs London without holding a planned news conference, we’re likely to hear much, much more about all of this from him, and soon — on Twitter.