Donald Trump and Kim Jong Un—the leaders of two countries that have technically been at war for the past seventy years—will make history, on Tuesday, just by shaking hands. They will meet at a luxury island resort, in Singapore, where peacocks strut the tropical grounds that were a pirates’ haven in the nineteenth century and a Japanese prisoner-of-war camp in the twentieth. Two days have been allocated for the summit, although Trump said, on Saturday, that he would know “within the first minute” if a deal is doable with the North Korean leader. “If I think it won’t happen I’m not going to waste my time,” Trump said at a press conference at the G-7 summit, in Canada. “I don’t want to waste his time.”

Within just five days, Trump is navigating two tough summits that may define his legacy, and even redefine the world order. The first summit—the G-7, with America’s six closest economic allies—didn’t end so well. The talks, in Quebec, were prickly at best. Tensions were captured in rival photos. In one, the German Chancellor, Angela Merkel, her hands planted on a table, loomed over a seated Trump, who glared back at her with his arms folded against his chest. It was tweeted by the summit’s German spokesman. Shortly thereafter, the White House released more than a dozen photos from the summit, including one showing the leaders of Britain, Canada, France, and Japan smiling as they huddled to listen to the American President.

Trump originally agreed to sign on to the joint G-7 communiqué. He boasted at a press conference, as he prepared to depart early, that relations with the Western allies were a “ten,” and that Canadian Prime Minister Justin Trudeau, the host, “did a really good job.” But a few hours later, in angry tweets sent from Air Force One, Trump abruptly withdrew from the communiqué because Trudeau, in comments after the summit, called the new U.S. tariffs “kind of insulting.” Trump lashed out at Trudeau for acting “so meek and mild” at the G-7, and called his Canadian counterpart “very dishonest & weak.” In a second tweet, he announced that the American team left behind in Canada had been instructed to pull out of the G-7 agreement. The reversal marked one of the rockiest conclusions to any G-7 since the alliance—which now represents nearly half of the global economy—was formed, in 1975.

The feud among friends, which has been building since Trump took office, is now fraying the alliance. Donald Tusk, the President of the European Council, issued a stark warning in Canada, as the G-7 nations gathered on Friday. “What worries me most, however, is the fact that the rules-based international order is being challenged, quite surprisingly, not by the usual suspects but by its main architect and guarantor: the U.S.,” he said. “We will not stop trying to convince our American friends and President Trump that undermining this order makes no sense at all. Because it would only play into the hands of those who seek a new, post-West order, where liberal democracy and fundamental freedoms would cease to exist.”

The diplomatic rupture even worried Republicans. Senator John McCain, of Arizona, who is fighting brain cancer, took time to tweet, “To our allies: bipartisan majorities of Americans remain pro-free trade, pro-globalization & supportive of alliances based on 70 years of shared values. Americans stand with you, even if our president doesn’t.”

Trump’s fury was directly related to the Singapore summit, U.S. officials acknowledged on Sunday. “If you attack this President, he’s going to fight back,” especially before the North Korea talks, Larry Kudlow, the director of Trump’s National Economic Council, said on CBS’s “Face the Nation.” “It is a historic negotiation, and there is no way this President is not going to stand strong. No. 1, he’s not going to allow the people to suddenly take pot shots at him hours before that summit.” On “Fox News Sunday,” Peter Navarro, a trade adviser to the White House, said, referring to Trudeau, “There’s a special place in hell for any foreign leader that engages in bad-faith diplomacy” with Trump.

It’s been a rocky year for Trump’s foreign policy. In May, he broke with the world’s five other major powers—Britain, China, France, Germany, and Russia—over the 2015 nuclear deal with Iran. A new Middle East peace plan, which the President once bragged was “not as difficult as people thought,” is still elusive. The Palestinians recalled their Ambassador to Washington, and balked at even talking with the White House after the U.S. Embassy in Israel moved, amid much fanfare last month, to Jerusalem.

The President’s overtures to the Russian President, Vladimir Putin, have also puzzled allies. This weekend, he urged the G-7 to re-admit Russia, which was expelled from the group after its invasion of Crimea, in 2014. The President appeared undeterred by strong evidence suggesting Moscow’s covert meddling in the 2016 U.S. election; its supplying the weaponry that shot down a Malaysian passenger plane over Ukraine, in 2014; its intervention in Syria’s civil war; or its annexation of Crimea. “So be it. We have to do business with Russia,” Kudlow said on CBS. “They’re part of the world story.”

Trump may now face even greater pressure than Kim does to pull off a success in Singapore. “Given the latest debacle with our allies, in Quebec, and a pending trade war, Trump needs a victory more than Kim, by far,” Bill Richardson, a former Democratic congressman and U.N. ambassador, who has travelled to North Korea eight times in twenty years, told me. “The Russia investigations and the failed congressional initiatives on health care and immigration add to the need for a dramatic foreign-policy success. Kim, on the other hand, already got what he mostly wanted: a meeting with the U.S. President, which will solidify his rule at home and make him a world player.”

Others don’t buy the “Wag the Dog” theory that the President needs a diversion from his many problems. Trump is instead tapping into initiatives by both North Korea and South Korea since January, some analysts say. Right time, right place—and right intervention.

“The momentum driving inter-Korean reconciliation—with both Korean leaders as catalysts—provided the impetus for Trump to see the opportunity to resolve decades-long security issues in northeast Asia, or, more cynically, achieve a Nobel Peace Prize,” Bruce Klingner, a former C.I.A. deputy division chief for Korea, who is now at the Heritage Foundation, told me. During the past couple of weeks, Trump has lowered the definition of success—and what denuclearization would entail. Washington has long defined it as “complete, verifiable, irreversible denuclearization,” or C.V.I.D. North Korea has previously defined it as lifting the U.S. “nuclear umbrella” that protects South Korea, the removal of twenty-eight thousand U.S. troops from South Korea, and the end of joint military exercises targeting North Korea.

“Rather than achieving C.V.I.D., Trump now defines ‘getting to know each other’ as the criteria for a successful summit,” Klingner added. “If the summit collapses, Trump could still define walking away as a ‘success,’ in that he was strong, and not weak like Obama, who signed a flawed nuclear deal with Iran.”