SEOUL (NYTIMES) - Rush-hour in South Korea's over-caffeinated capital runs at a frenzy - so it was remarkable to see commuters freeze Friday morning and fixate on giant Samsung television screens showing the scene unfolding in the Demilitarized Zone, where time stopped in 1953.
Kim Jong Un, in a black Mao suit, stepped across a low concrete barrier into the South Korean territory, a first for a North Korean leader since the catastrophic and unfinished war seven decades ago. He reached out to the South's president, Moon Jae In, and led him back over into the North's territory.
It was a reminder, if anyone here needed one, that the 34-year-old Kim has played the master choreographer in this remarkable dance step along a nuclear precipice.
Kim silenced those who thought he was too young and callow to rule by executing his uncle, fatally poisoning a half brother, installing his own generals and putting North Korea's nuclear and missile programs into overdrive.
And after spending 2017 proving that his backward nation could hurl missiles across the Pacific, and could test a weapon many times more powerful than the Hiroshima atomic bomb, Kim seized on an invitation from South Korea to take part in the 2018 Winter Olympics and suddenly played the statesman. On Friday he hinted anew that his nuclear arsenal might be on the table, if the price was right.
President Donald Trump insists that his own actions are responsible, that his threats of "fire and fury" and, more important, his intensified sanctions, forced Kim to this moment. He is partly right: Trump has shown an energy in confronting North Korea that President Barack Obama never did.
But disarmament experts who watched the Korean leaders meet in the DMZ agreed that Kim had been driving the events.
Kim has learned the art of surprise as surely as his grandfather, Kim Il Sung, North Korea's founder and the younger Kim's role model, did. The elder Kim caught the world unawares by invading the South in June 1950.
The Friday encounter did everything it was supposed to do to set up the next summit meeting, between Kim and Trump. That is the moment, South Koreans say, for any nuclear deal to be struck, something that can only happen when a US president is in the room.
The question is whether Kim is really ready to make that deal, or whether he is betting, as most experts think he is, that he can get help to normalise the North's economy while keeping at least parts of a fearsome arsenal that he believes has kept the Kim family in power.
The agreement published on Friday (April 27)afternoon, as the two Korean leaders headed into a dinner that was rich in symbolism about the common traditions of the North and South, says little on the nuclear topic.
It sets a deadline of completing some kind of peace arrangement - not necessarily a treaty - by the end of this year. But it sets no schedule for denuclearisation.
That is a critical point, because until now the Trump administration's position has been that the North must surrender all its weapons first, and that any talk of treaties or trade, or sanctions relief, would come only when its weapons, its uranium and plutonium and its missiles are securely out of the country.
Moon's advisers insisted that the vagueness of the agreement published on Friday was a virtue, not a defect, and that it would be up to others to work out the details. But they also insist that "Chairman Kim," as they called the young leader, is driven by different imperatives than his father and grandfather were.
"They want a Trump Tower and a McDonald's," Moon Chung In, a special adviser to the South Korean president, insisted in an interview with Christiane Amanpour on CNN on Friday.
Perhaps they do - the North's most famous hotel, in Pyongyang, the capital, leans so dangerously that it was never opened, and North Korea is not known for its fast-food chains. But ask the people who have seen past peace initiatives whether they think this one will work out any differently, and they have serious doubts that Kim will give up his nuclear program for any price.
Among the sceptics is Trump's new secretary of state, Mike Pompeo, who made a secret visit to Pyongyang over Easter weekend to try to gauge Kim's sincerity. Last summer, it was Pompeo, then still the CIA director, who argued that the only way to deal with North Korea was to separate Kim from his weapons, a comment some interpreted as advocating regime change.
On Friday at NATO, on his first full day as secretary of state, Pompeo suggested for the first time that the North Korean leader was ready to deal.
"I did get a sense that he was serious," he told reporters.
"The economic pressure that has been put in place by this global effort that President Trump has led has led him to believe that it's in his best interest to come to the table and talk about denuclearisation."
Yet talking is different from denuclearising.
And talking about denuclearising is hardly new. The North promised the same in a 1992 agreement, and many in Seoul, the South's capital, wondered then if the nightmare of living under the constant threat of artillery barrage was about to end.
In fact, the agreement reached on Friday picks up language from the 1992 accord, and has similar provisions about reuniting families separated during the Korean War and non-aggression agreements. Little of it happened.
There were two agreements with the George W. Bush administration, each described at the time as breakthroughs. Since then the North has amassed 20 to 60 nuclear weapons, up from zero when those commitments were made.
No one knows those numbers better than Pompeo, who spent a lot of time with the CIA's Korea Mission unit, assessing the scope and imminence of its nuclear capabilities. "There's a lot of history here, where promises have been made, hopes have been raised and then dashed," the new secretary of state told reporters.
Trump's solution to not getting "played", the phrase he so often uses about his predecessors and North Korea, is to keep what he calls a "maximum pressure campaign" on the North until denuclearization happens.
The South Koreans say they agree. But the documents issued on Friday hint at benefits that begin to flow to the North as they move towards a peace agreement, and a reduction of tensions.
China, which is largely interested in maintaining the status quo, could also loosen the restrictions on oil and goods, as long as negotiations play out.
All this suggests that Trump's challenge when he meets Kim, probably in early June, is growing.
He must establish the process for the actual dismantlement of weapons, the removal of stockpiled uranium and plutonium bomb fuel from the country and a verification program that will be one of the most complex in history, given the vastness of North Korea's mountains.
In short, Trump must do better than Obama did in the Iran deal, an agreement Trump believes is so flawed it should be abandoned.
What no one knows yet is the kind of concessions Kim is hoping to demand in return.
Han Sung Joo, a former South Korean foreign minister who negotiated with the North for much of his career, says he believes he knows where this is headed.
"If Kim Jong Un indeed came up with the idea of the so-called peace momentum getting started, it was indeed a jackpot of an idea," Han said this week.
Kim's goals, Han said, will be to "weaken international sanctions", draw serious investment into the North and make the country's nuclear status "a fait accompli."
Trump, in contrast, says he will solve the North Korea problem, once and for all. After Friday's meeting, he will now face the task of explaining how.