Kim Jong Un had a request. As Donald Trump wooed the North Korean leader inside a former British garrison in Singapore, Kim asked Trump to suspend military exercises by U.S. and South Korean forces on the Korean Peninsula, long a source of concern for Pyongyang’s hair-trigger military. It wasn’t something that had been negotiated by their staffs, and some of Trump’s aides were concerned that the concession would irritate allies. But he calculated that it was worth the risk, and without consulting anyone further, he told Kim on the spot that he’d do it.

It was exactly the kind of shoot-from-the-hip move they hate in the pin-striped confines of the State Department. But the moment was classic Trump. “I’ll do whatever it takes to make the world a safer place,” he said in a press conference after the summit, in response to a question from TIME. “If I can save millions of lives by coming here, sitting down and establishing a relationship with someone who’s a very powerful man, who’s got firm control of a country and that country has very powerful nuclear weapons, it’s my honor to do it.”

The war-game concession was just the latest in a series of surprising turns in what may ultimately prove to be a historic moment. Since inspectors from the International Atomic Energy Agency were blocked from visiting North Korean nuclear sites during the first term of Bill Clinton’s presidency, the U.S. and its allies have struggled with the growing threat of a nuclear-armed North Korea. Multiparty agreements, crippling sanctions and threats of military intervention have failed to prevent the totalitarian state from approaching the ability to strike the U.S. with a nuclear-tipped missile.

Now, in less than a year, Trump has gone from threatening Kim with annihilation to the first face-to-face talks between a sitting U.S. President and a North Korean leader. The result was mixed. Trump touted his “terrific relationship” with Kim, a verbal promise Kim gave him that he was destroying a missile-engine test site and Kim’s “unwavering commitment to complete denuclearization of the Korean Peninsula.” Trump also secured the return of the remains of 5,300 service members who died during the Korean War. But experts pointed out that Kim had made only vague promises of the kind that Pyongyang had violated multiple times before.

The summit theater was the latest and most dramatic example of how the impulsive President is upending the global order. Three days earlier, as he flew to Singapore aboard Air Force One after a testy, two-day economic summit with six of the U.S.’s closest allies, Trump had grown livid as he watched Canadian Prime Minster Justin Trudeau declare that the new U.S. trade tariffs were unfair. Scowling at the flat-screen TV in the plane’s private office, according to a White House official, Trump ordered his aides to back out of the summit’s final communiqué, which had already been publicly released after two days of negotiations. The move was met with stunned protest from Ottawa to London to Paris. But that’s how things work now. With each feat of showmanship or fit of pique, Trump is redefining America’s role on the world stage.

Early on, Trump heeded his top aides when they urged caution. But in the past six months, he has taken increasingly dramatic risks–especially in foreign policy. In December, Trump committed to moving the U.S. embassy from Tel Aviv to Jerusalem, overriding the dire predictions about Middle East chaos. In March, he threatened to impose stiff trade tariffs on China and Europe, then enacted them two months later after global markets generally bounced back from initial losses. In May, he withdrew the U.S. from the 2015 nuclear deal with Iran, even though Europe, international agencies and some of his own senior aides said Iran was complying with it.

The populist has famously bristled at convention. “If you go into a meeting and say we can’t do that, or that’s not the way it’s been done, you can be assured he’s going to want to do it,” says one senior National Security Council official. “He thinks the way it’s been done is wrong and stupid and won’t work.” But lately Trump has become increasingly energized by the idea that he’s shattering precedent, and feels vindicated by the results of his risky moves, according to interviews with more than a dozen friends, aides and former officials. “He recognizes that people always are running around, it seems, with their hair on fire,” senior White House aide Kellyanne Conway told TIME. “He sees that all those attempts [by past Administrations] have been failures, and they have been aborted promises. So he says, ‘Let’s just try it a different way.'”

There may be short-term benefits in abandoning the U.S.’s decades-old commitment to strategic predictability. But foreign-policy experts at both ends of the political spectrum are worried about the costs. “Rattling allies undermines decades of strategic certainty” in international affairs, says Mark Dubowitz, CEO of the hawkish Foundation for Defense of Democracies. Already, other countries are retaliating with trade tariffs that could boost prices at home, slow the global economy and spike unemployment. Trump’s backing of Sunni and Israeli moves against Iran, in addition to his withdrawal from the 2015 nuclear deal, are encouraging a dangerous proxy war in the Middle East, where over 25,000 U.S. troops remain deployed.

Nowhere are the stakes are higher than in North Korea, where diplomatic failure could set the course for renewed military confrontation. If Trump misplays his hand, it could endanger millions of lives.

For those who have known the President for years, his handling of the summit was trademark Trump: casting aside strategic prudence for a theatrical gesture, with an impulsiveness rooted in the belief that he alone could cut the big deal. This confidence was visible seven years ago, at the 2011 White House Correspondents’ Association dinner, when Trump was already thinking about launching a campaign for the presidency, according to those who saw him in action that night.

During a 10-minute conversation at a table in the center of the ballroom, Trump asked Nick Ayers, who was then a young Republican strategist and is now Vice President Mike Pence’s chief of staff, questions about the mechanics of presidential campaigns and political organizations and committees, according to a person at the dinner. Later in the evening, Trump sat stone-faced as comedian Seth Meyers skewered Trump for his questions about President Obama’s birthplace and said he was surprised Trump was running as a Republican because “I just assumed he was running as a joke.”

Five years later, in July 2016, Ayers was swept into Trump’s campaign effort as part of Pence’s team. The day after Trump won the election, Ayers asked Trump if he recalled their conversation that night, according to a person close to Trump who was in the room. Trump said it was one of two or three moments that convinced him to launch a full-fledged bid for the White House. He heard the punch lines as a challenge. “Oh yeah, you think I can’t do it?” the person said, describing Trump’s reaction. “Watch me do it.”

Trump wasted no time tossing diplomatic conventions overboard. The day after the 2016 election, Japan’s Prime Minister Shinzo Abe called Trump on his personal cell phone. Trump was in his office with a handful of senior aides and put Abe on speakerphone. After exchanging pleasantries, Trump said what he often tells acquaintances: if Abe were ever in New York, he should look him up. Abe said he would be in New York the following week. So Trump agreed to meet him, violating a long-standing tradition that a President-elect doesn’t meet with foreign leaders until they’ve taken the oath of office. The Obama White House was apoplectic. But Trump wouldn’t cancel the meeting. The sit-down with Abe initiated what would become Trump’s closest relationship with a world leader and set the tone for his engagement with Asian powers.

Trump’s first year in office was marked by running battles between his instincts and his aides. Some White House staffers appealed to the President’s gut, while others tried to outmaneuver or wait out the President’s impulses. In order to manage Trump’s behavior in briefings, for example, his second National Security Adviser, H.R. McMaster, began having aides prepare cards that answered four basic questions: Why are we doing this? What will it cost? What are others paying or doing? And what happens next?

For a while, it worked. In the summer of 2017, Trump repeatedly demanded to know why the U.S. was still in Afghanistan after toppling the Taliban government in 2001, but ultimately agreed to boost troop levels there, in line with Establishment thinking. He groused in response to the litany of concerns voiced by aides about moving the U.S. embassy to Jerusalem, which his transition staff had prepared for him to do on his first day in office. But he deferred action on the move. He complained that bureaucrats were overstating the potential fallout of ditching the Iran nuclear deal, but put off pulling out of it as he had promised to do during the campaign.

When aides like Tillerson, Defense Secretary James Mattis and Trump’s former economic adviser Gary Cohn succeeded in suppressing his instincts, it came at a cost. Trump railed against his Cabinet secretaries and staff. The Iran deal was a source of particular frustration. Thanks to the checks Republicans placed on the deal when Obama signed it, Trump was required every three months to certify that Iran was complying with the agreement. Advisers predicted that European markets would tank if Trump didn’t. Feeling boxed in, the President demanded other options. In July 2017, with another three-month certification looming, Trump’s national-security staff had none to offer. Trump exploded. “This is never f-cking happening again,” he said, according to two people familiar with the meeting.

Against this backdrop, the President shook up his inner circle, firing chief of staff Reince Priebus and replacing him with Homeland Security boss John Kelly. In exchange for imposing discipline, the retired Marine general demanded tight control over the White House decisionmaking process. For a while, Kelly’s guardrails constrained Trump. But over time they, too, have failed.

Much of the slippage came on the domestic front, with Trump lashing out more frequently and harshly at special counsel Robert Mueller’s investigation into his campaign’s contacts with Russian officials, demanding the deployment of National Guard troops to the border and announcing pardons with little input from the Justice Department or his staff.

But arguably the biggest breaks have come on foreign policy. When Trump took office, the State Department sent a document to the White House predicting that dozens of U.S. embassies would be overrun with protesters if Trump decided to recognize Jerusalem as Israel’s capital. Tillerson stuck to that line so hard that around the West Wing he become known as the Doomsayer, according to a White House official.

The issue came to a head near the end of the year, when Trump pushed the case and Tillerson demurred. Diplomats from Egypt, Jordan and Saudi Arabia warned the White House that their leaders would issue forceful objections if Trump went forward, citing fears that formally acknowledging Jerusalem would spark violent clashes over the ownership of a city that has long been a lightning rod for religious and nationalist passions. But on Dec. 6, Trump announced that the embassy would move, and now many White House officials feel that the dire warnings were overblown.

The jockeying wasn’t done. Officials tried to stall the move. At a rally on May 10 in Elkhart, Ind., Trump himself described one such attempt, saying advisers told him it would cost $1 billion and take years to complete. He said he called the U.S. Ambassador to Israel, David Friedman, who told Trump he could move the embassy into an existing building in Jerusalem for $150,000. “David, you can do that from $1 billion to $150,000. You know what? Spend $200,000 or $300,000–that’s O.K. too,” Trump said. Friedman’s move was largely symbolic: he had a large stone plaque installed on an existing consular office and transferred some staff from the existing embassy in Tel Aviv to populate it.

By the time Trump walked away from the Iran deal, it was clear that the dam had broken during the previous five months and that a two-week period in early March had been particularly telling. On March 1, Trump announced new aluminum and steel tariffs on Europe and China. On March 13, he replaced Tillerson with his hawkish CIA director, Mike Pompeo.

It was right in the middle of this period that a special envoy from South Korea arrived in Washington on March 8, with a message so urgent and sensitive, it needed to be delivered in person.

The door to the Oval Office clicked shut. The South Korean envoy had told Trump that Kim Jong Un wanted to meet him as soon as possible. Would Trump accept? The President turned to the handful of senior advisers and jutted out his chin in what aides have come to recognize as a sign that he’s about to say something provocative. “I’m inclined to do it,” Trump said. “What do you think?”

There were a million reasons to say no, and as the South Korean envoy cooled his heels across the hall in the Roosevelt Room, Trump’s aides took turns listing them, according to two U.S. officials briefed on the meeting. For years, the U.S. had refused to reward North Korea’s treaty-violating pursuit of nuclear weapons and intercontinental ballistic missiles; a face-to-face meeting would seem to do just that. Moreover, with little time to plan tactics and strategy, or to demand concessions, there was no way to tell what Kim might give up in return. Worst of all, if talks proved that there could be no diplomatic solution to the standoff, then military conflict–even nuclear war–could become more likely.

But in a matter of minutes, Trump had made up his mind. By quickly saying yes to a meeting, the President thought, he would test Kim’s intentions and put him off-balance, explains a close aide. Trump summoned the South Korean diplomats into the Oval Office and beamed. “Let’s do it, fellas,” the President said.

Trump wasn’t done surprising his staff or his South Korean guests. He had, in some ways, internalized the concerns of his aides. The South Koreans assured Trump that Kim was open to giving up his nukes, wouldn’t object to U.S.-Korean military exercises and promised to stop nuclear and missile tests. But none of that was in writing. Trump wanted to protect himself. So as he sat with the South Korean envoy, national-security adviser Chung Eui-yong, in the armchairs before the Oval Office fireplace, Trump made an unusual proposal. “Here’s an idea: how about you make the announcement,” Trump said, according to the officials.

It went against long-standing diplomatic protocol for an ally to speak on behalf of the U.S. President. But while White House aides helped draft a statement for Chung to read, the jet-lagged diplomat called his boss, South Korean President Moon Jae-in. Just after 7 p.m.–two hours after delivering the message from Kim–Chung walked into the West Wing driveway and announced that Trump had agreed to meet the brutal dictator.

It was only the beginning of a diplomatic dance that would stun foreign-policy experts. Pompeo made two surprise trips to Pyongyang and brought back three freed American prisoners. Asked on May 9 if he deserved the Nobel Peace Prize, Trump replied, “Everyone thinks so, but I would never say it.” It was clear that he was beginning to enjoy himself.

But it turned out that dealing with North Korea might not be so easy. Late one Wednesday night at the end of May, Trump’s national-security team told him a North Korean official had called Pence a “political dummy” and threatened a nuclear “showdown.” On top of that, the delegation the President had sent to Singapore two weeks earlier to hammer out the summit details had been stood up. North Korea had gone radio-silent for more than a week.

It was starting to look like the summit would be a diplomatic and public relations disaster.

Trump decided to sleep on it. The next morning, after firing off two tweets alleging without proof that the FBI had sent a spy to infiltrate his campaign, Trump personally dictated a letter to Kim that announced he was canceling the summit. The letter, equal parts wistful and threatening, called Kim “His Excellency,” but pointedly noted that the U.S. President was hoping not to have to use America’s “massive and powerful” nuclear capabilities against the young dictator.

Just over a week later, North Korea’s No. 2 official, Kim Yong Chol, walked into the Oval Office and personally presented Trump with a letter the size of a legal pad. The summit was back on.

To his fans, Trump’s growing international disruptions are a welcome development. “That’s exactly what we were hoping for when he was a candidate–someone who acts less like a politician and more like a businessman, someone who sees the field and makes a decision,” says Eric Bolling, a former Fox News anchor and early campaign supporter who regularly speaks to Trump and believes the President’s unpredictability keeps foreign leaders off guard.

Of course, Trump is hardly the first President to make decisions spontaneously. President George H.W. Bush surprised his staff in 1990 when he drew a red line after Saddam Hussein’s invasion of Kuwait, telling reporters on the South Lawn of the White House that Iraq’s aggression “will not stand,” and setting the stage for the first Gulf War. President Richard Nixon unexpectedly created what is now a long-standing U.S. policy of not negotiating with terrorists when, faced with questions from reporters about two U.S. diplomats and three others held hostage in Sudan in 1973, he said the U.S. “will not pay blackmail.”

But in previous Administrations, these types of incidents were rare. “This President is interacting on an hourly basis, and there is no filter,” says Timothy Naftali, a presidential historian at New York University. “There are no staffers between his impulses and his Twitter finger.” Trump is burning up political capital in the process. “The White House is historically designed in order to limit the risk of embarrassment,” Naftali says. “If he would use his staff better, he wouldn’t find himself in these embarrassing positions.”

There costs are mounting. In the wake of Trump’s break with the other G-7 countries ahead of the Singapore summit, the French government suggested Trump had acted rashly and out of anger, and criticized his inconsistency. Canada’s Parliament unanimously condemned Trump’s criticisms of Trudeau and backed the government’s hardening stance over the NAFTA negotiations.

And while the Middle East hasn’t yet blown up over Trump’s Jerusalem embassy move or his departure from the Iran deal, both are proving destabilizing. Protests along Israel’s border with Gaza have claimed more than 100 lives, and have raised concerns in Cairo that the unrest could spread to the border with neighboring Egypt. European and Chinese attempts to salvage the Iran deal are faltering, and Iran says it will increase its uranium enrichment capacity now that the U.S. has abandoned the pact.

In the case of another potential summit with North Korea, embarrassment could prove even more costly. Trump billed the Singapore meeting as just the first of several. But longtime U.S. intelligence analysts are concerned that Kim may use drawn-out talks to further advance his nuclear program, as North Korea has done in the past.

There’s also a concern that talks may implode if Trump feels slighted, as he did after the G-7 meeting. This time the fallout would do more than bruise the U.S.’s relationships with its steadiest allies; it would endanger millions of lives on the Korean Peninsula. In addition to an arsenal of atomic bombs secreted away in underground tunnels across the country, North Korea has approximately 11,000 pieces of artillery aimed at Seoul from the mountains north of the demilitarized zone. Destroying those positions would take days, during which bombs would be raining down on the Seoul metropolitan area’s population of 25 million.

“The danger is that he is approaching this almost as a reality show,” says Jeffrey Prescott, a former senior National Security Council official under Obama. “He’s thinking about the short-term benefit he could get from the pageantry of the summit itself and could lose sight of the substance of the threat.” Kim wants to be seen on equal footing with the U.S. and, ultimately, secure a guarantee that the U.S. won’t attack and will eventually leave the Korean Peninsula.

There is another possibility: that through chance, shifting interests and the mix of Kim’s strategy and Trump’s spontaneity, the Singapore summit will represent a real breakthrough. When Trump took office, Washington elites were arguing over two options for dealing with Kim’s nukes: military intervention or learning to live with a nuclear North Korea through deterrence. This summit, for all its showmanship, may very well leave the U.S. better positioned than either of those offerings. Trump’s “diplomacy, however unconventional, has pierced the isolation bubble of the North Korean leadership, which no previous President could do,” wrote Victor Cha, President George W. Bush’s director for Asian affairs at the National Security Council from 2004 to 2007, in the New York Times on June 12.

On his way back to the White House from Air Force One after departing from Singapore, Trump was in a defiant, even ebullient, mood. In defense of his cancellation of the military exercises, for example, he tweeted at his critics, “We save a fortune by not doing war games, as long as we are negotiating in good faith–which both sides are.” A few in Washington agreed, including some Democrats. But there were plenty who saw in Trump’s latest impulsive moves a dangerous trend. The President rolls the die, breaks diplomatic norms and relishes the fact that predicted catastrophe doesn’t come to pass. Which is fine unless it does.

This appears in the June 25, 2018 issue of TIME.

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