President Donald Trump and North Korean autocrat Kim Jong Un have arrived in Singapore ahead of the big show — an unprecedented meeting between Washington and Pyongyang’s leaders that could, if things go well, pave the way for a historic rapprochement and the eventual end of the last major frozen conflict of the Cold War.

But while their Tuesday summit is this week’s headline event, the opening act left many observers fearing the worst.

Trump’s two-day stop in Quebec for a meeting with the leaders of the Group of Seven industrial nations was exactly the fiasco many feared. On Friday, Trump told reporters that Russia should be welcomed back into the group, which ejected Moscow after its 2014 annexation of Crimea. On Saturday evening, after leaving early to head to Singapore, Trump said he was pulling out of the summit’s joint communique because of comments by Canadian Prime Minister Justin Trudeau.

Trump tweeted “Based on Justin’s false statements at his news conference, and the fact that Canada is charging massive Tariffs to our U.S. farmers, workers and companies, I have instructed our U.S. Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the U.S. Market!”

Trump tweeted “PM Justin Trudeau of Canada acted so meek and mild during our @G7meetings only to give a news conference after I left saying that, ‘US Tariffs were kind of insulting’ and he ‘will not be pushed around.’ Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!”

According to accounts of the G-7 meeting, officials from other members of the bloc confronted Trump with a torrent of statistics about the importance of the U.S.-authored international order and the merits of free trade. They watered down the joint communique — scaling back comments on issues of climate and other concerns of the liberal order — in a bid to get Trump on board. But after briefly relenting, he shrugged off these many facts in favor of his feelings, sticking to his protectionist instincts.

A host of analysts argued that Trump’s view of global trade (and posturing over Canada’s own tariffs) was both misguided and ahistorical. “Right now, the level of tariffs on trade in goods around the world is lower than it has been for 150 years,” said Adam Posen, president of the Peterson Institute for International Economics, to the Financial Times, “and that is due to the path of U.S. policy over the last 75 years.”

A now iconic image, first circulated by aides of German Chancellor Angela Merkel, showed a tense scene in which world leaders confronted Trump. The tableau, likened to a Baroque painting, was hailed by Trump’s allies and detractors alike.

John Bolton tweeted “Just another #G7where other countries expect America will always be their bank. The President made it clear today. No more.”

Guy Verhofstadt tweeted “Just tell us what Vladimir has on you. Maybe we can help.”

The rancor cemented the impression that Trump is actively unraveling the unity of the West.

“It was not a surprise,” said Norbert Röttgen, the chairman of the foreign affairs committee in Germany’s Parliament, to my colleagues. “The president acted and reacted in the childish way he could be expected to.”

“How is it possible to work this way if once you have agreed to something, two hours later the guy decides he doesn’t agree with what he agreed with?” said François Heisbourg, a former French presidential national security adviser, to The Post. “Is there any space for a multilateral order under these circumstances?”

Trump, of course, is not interested in talk of multilateralism. His decision to meet Kim in Singapore is almost entirely drawn from a desire for personal glory. Far more satisfying than a turgid annual summit and the lecturing of other leaders, it’s an opportunity to make genuine history and, as Trump himself suggested, perhaps win a Nobel Prize.

In that vein, Trump has a lot in common with his counterpart from Pyongyang. “Thin-skinned alphas, both men are wedded to a go-it-alone leadership style, have a penchant for bombast and are determined to project dominance when they finally meet,” wrote my colleague Philip Rucker.

Kim “constantly feels like he has to prove himself, and in that sense he’s going to do what no other North Korean leader has done, and that is command an audience with the president of the United States,” said Victor Cha, a National Security Council official in the George W. Bush administration official and former nominee to be Trump’s ambassador in Seoul, to Rucker. “And for Trump, this is the only diplomacy that he’s doing in the whole world right now. Everywhere else he’s either walking out of agreements or sanctioning countries. ... This is Trump’s only chance to make a mark as a statesman.”

But this impulse, experts caution, is precisely what may undermine a lasting agreement. “This mix of reality TV antics and Trumpian disruption has characterized the entire run-up to the summit, generating endless TV talking-points, but little actual movement on the technical issues,” noted Robert Kelly, a professor of international affairs at Pusan National University in South Korea. “Indeed, Trump’s bragging about how he had forced the North Koreans to agree to talks and the speculation about a Nobel almost certainly worsened the negotiations.”

Many analysts believe the meeting will be heavy on theatrics and light on substance. The two sides may come up with a statement that includes both commitments to North Korean “denuclearization” and a process that could lead to a formal peace treaty with South Korea. But skepticism abounds over the possibility of monitoring North Korea’s nuclear program - not to mention Pyongyang’s willingness to follow through on its promises.

Of course, while Pyongyang is eager for economic relief and the end of sanctions, Kim may consider the summit itself the real coup. “This unprecedented meeting with the U.S. president will make Kim Jong Un feel very proud, having achieved something his father and grandfather didn’t,” said Joo Seong-ha, a North Korean defector turned Seoul-based commentator, to my colleague Anna Fifield.

No matter what happens, the outcome could be dangerous. After the debacle at the G-7, experts fear Trump may be desperate for a real victory. And in the rush to champion a successful deal, he could consider concessions to Kim that would only strengthen a nuclear-armed dictatorship.

And if things simply fall apart, we’re in for a period of rapidly spiking tensions in Northeast Asia. “If there is no statement of intentions to move toward a peace treaty, if there’s no statement from the North Korean side on denuclearization,” argued Ryan Hass of the Brookings Institution in a briefing to reporters last week, “we’re going to find ourselves in a very hollow summit and I think that quickly we’ll move into ... finger-pointing about whose fault it was.”

At least on this count, Trump’s erstwhile allies in the West can certainly relate.

Ishaan Tharoor |The Washington Post

Ishaan Tharoor writes about foreign affairs for The Washington Post. He previously was a senior editor and correspondent at Time magazine, based first in Hong Kong and later in New York. Follow Ishaan on Twitter @ishaantharoor.