In a breathtaking gambit that surprised his closest advisers, President Trump, almost impulsively, accepted an invitation on Thursday to meet the North Korean leader Kim Jong Un—by May—to discuss how to defuse the world’s most dangerous nuclear standoff. The invitation was relayed by a South Korean delegation that met with Kim earlier this week and then travelled to Washington. It will be the first-ever meeting between American and North Korean heads of state. The location is yet to be designated, but the odds are that it will be a South Korean or Chinese venue.

Unless the summit is just an extraordinary photo opportunity to symbolize the easing of tensions or a simple listening tour, the new U.S.-North Korean track is backward diplomatically. A summit of leaders is usually the reward rather than the starting point. Normally, months or even years of diplomatic legwork are required to work out terms to be formally approved by heads of state. The Clinton Administration spent years working on phases of a deal to curtail North Korea’s nuclear and missile programs, which included a trip by Secretary of State Madeleine Albright to Pyongyang. A visit by President Clinton was supposed to be the final deal-maker.

As it is currently set up, President Trump has everything to lose if he comes away without tangible and extensive gains that meet his long-standing demand for North Korea to abandon the world’s deadliest weapon. Kim, who leads the world’s most isolated country, has everything to gain from the stature that comes from a summit with the world’s leading superpower.

North Korea’s wily charm offensive this year, and President Trump’s willingness to embrace it, are stunning reversals after a torrent of threats during the final months of 2017. At his United Nations début, in September, President Trump described Kim Jong Un as a “rocket man” on a “suicide mission.” The United States would have “no choice but to totally destroy North Korea” if it had to defend itself or its allies, he said. Kim countered by labelling Trump a “mentally deranged U.S. dotard.” The President’s speech “convinced me, rather than frightening or stopping me, that the path I chose is correct, and that it is the one I have to follow to the last,” he said.

In October, Trump tweeted, “I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man....” And just hours before the surprise announcement on Thursday, Tillerson told a press conference in Addis Ababa, Ethiopia, that the United States was “still a long ways from negotiations” with North Korea. “We just need to be very clear-eyed and realistic about it.” The first step, he predicted, would be talks about talks.

Trump’s historic decision unfolded in just a matter of hours—and it was also highly unusual. It followed a meeting with Chung Eui-yong, the national-security adviser to South Korean President Moon Jae-in. President Trump seemed so excited about his decision that he ducked into the White House press room to announce that the South Korean official would have an important statement at 7 P.M.—but provided no details. Speaking at the press stakeout outside the White House, Chung told reporters, “I explained to President Trump that his leadership and his maximum pressure policy, together with international solidarity, brought us to this juncture.”

In a statement, the White House press secretary Sarah Huckabee Sanders said that the President “greatly appreciates the nice words” of the South Korean delegation. “We look forward to the denuclearization of North Korea. In the meantime, all sanctions and maximum pressure must remain.”

The biggest unanswered question is what North Korea wants in exchange for scrapping its nuclear weapons. It could include an end to military exercises between the United States and South Korea, the withdrawal of U.S. forces from the Korean Peninsula, a formal peace treaty to end the Korean War, normalization of diplomatic relations, guarantees of non-aggression, an end to economic sanctions, and possibly economic aid.

In some ways, it’s an offer—and an opportunity—that’s impossible to refuse. Diplomacy to eliminate the North’s weapons has been an American goal for more than two decades. President Trump is the latest in a long line of Presidents—dating back to Harry Truman—to navigate the enigmatic regime in North Korea, which has been ruled by three generations of the Kim dynasty for seven decades. In 1950, President Truman announced his willingness to use an atomic bomb—“every weapon that we have”—against North Korea during the war to prevent Communist aggression on the South.

At the same time, diplomacy has never fully succeeded, despite assorted pledges and pacts during the previous three Administrations. And the stakes today are much higher. “Diplomacy is much tougher now than it’s ever been because the North Koreans have nuclear weapons and the means to deliver them,” Wendy Sherman, who worked on the North Korea portfolio in the Clinton and Obama Administrations, told me. Sherman accompanied Albright to Pyongyang, in 2000, on the only trip made there by a ranking U.S. official since the end of the Korean War. (I was on that trip, too.)

Last year alone, the North conducted more than two-dozen missile tests, including the test of a missile capable of reaching any part of the United States, and tested a hydrogen bomb—adding to its arsenal of atomic bombs. “The North Koreans have much more leverage than before,” Sherman said. “Comparisons to the past are useful but they’re not adequate for where we are right now.”

American Presidents have long vowed to block proliferation of the world’s deadliest weapon. But brokering deals has consistently been their most frustrating foreign-policy challenge. In 1984, President Reagan bluntly warned Pakistan against developing a bomb. But it did, conducting its first nuclear test in 1998. President Clinton pledged that North Korea would not get the bomb “even at the risk of war.” But it did, conducting its first test in 2006. President George W. Bush vowed that Iran would not get the capacity to build a nuclear weapon. But it did, although U.S. intelligence believed it was still at least months away from a bomb when a nuclear deal was struck in 2015.

The U.S. track record with North Korea is the longest and most tortured. The first breakthrough was in 1994, when the Clinton Administration brokered the Agreed Framework. North Korea promised to immediately freeze and eventually dismantle its nuclear program, which included two reactors under construction that Washington was concerned could produce fuel for a bomb. In turn, Pyongyang would receive energy substitutes—heavy fuel oil in the short-term and the eventual construction of two light-water reactors not able to produce fuel for a nuclear weapon.

“North Korea did not produce one additional ounce of fissile material, no nuclear weapons and no ballistic missiles during the Clinton Administration,” Sherman said. But the deal proved to be too complex and time-consuming. “We moved very slowly on the Framework,” she said. “We didn’t realize how hard it was to do, so there were all kinds of problems and slowdowns. Using a [international] consortium to build and finance a [light-water] reactor was not easy. We also didn’t really move to normalize relations, which is what was expected by the North.” The deal also got caught up in domestic politics. The accord coincided with the 1994 Republican sweep of Congress, known as the Republican Revolution. “The Republicans never liked it anyway,” Sherman said.