White House officials were “dazed,” as were the foreign-policy experts I spoke with. “In a classic negotiation, the summit is the last piece, not the first piece, and so in terms of procedure, this is very unusual,” a former senior U.S. official told me. And already, there are signs that the White House may be walking back Trump’s tweet. When asked Friday about the arrangement and whether it would be anything more than a “photo-op” that benefits Kim, press secretary Sarah Huckabee Sanders responded that Trump “will not have the meeting without seeing concrete steps and concrete actions take place by North Korea.”

Still, there are indications that Trump’s impulsivity could work to his benefit. “You can see why [agreeing to a meeting] is attractive to Trump because it makes him swashbuckling,” the former official said. “It makes him creative, he is throwing out the playbook and doing something new.” That could be an asset, given that three successive U.S. administrations have failed to thwart three successive generations of Kims. That “doesn’t mean that the old rules simply go away,” the senior official cautioned. “It means that what he has done is that he has given away the most important deliverable before he starts.” But it also means that the U.S. may have a once-in-a-generation chance to end the stalemate on the Korean peninsula—if the Trump administration can figure out what it, and Kim, really want.

What does Kim want?

In exchange for Trump agreeing to meet Kim, the South Korean envoys said that North Korea would consider denuclearization, agree to cease weapons testing (for now), and not react to planned U.S.-South Korea military exercises set to begin this spring. But it is unclear what the North Korean regime is seeking in exchange, or even what these stipulations entail. “Usually what happens when you go into these negotiations is there is enormous preparation that takes place,” the former U.S. official told me. “One of the dangers that traditional diplomats will see here, and I am among them, is if you are not systematic in the way that you plan, then when the principles get together, what they agree to can be both unpredictable—that is not necessarily bad—but then the understanding that they come to, about what the next steps are, can be very murky or even contradictory.”

The entire negotiation, of course, hinges on what North Korea means by “considering” denuclearization. And experts doubt that Kim is really saying what Trump wants to hear. “Here is the big gamble that the president is making: Is Kim really likely to give up his nuclear weapons?” said Nicholas Burns, who served in both the Clinton and Bush administrations. “The answer is no. It would not be rational for him to give up his nuclear weapons. It is the only card he has.” For years, North Korea has worked to build a nuclear weapon capable of striking the United States for one specific reason: to have a credible deterrent against invasion. “He knows what happened to Qaddafi and he knows what happened to Saddam Hussein when they gave up their weapons of mass destruction,” Burns continued. “They lost their lives, and regimes, and families.”

The prospect of a Trump-Kim summit suggests that North Korea’s calculus has changed. But the total lack of context and timeframe means that the Trump administration is in the dark. “What I imagine they meant is that at some point in the process of talks they will be willing to discuss denuclearization. That could be months from now, but that could also be a year from now,” said Suzanne DiMaggio, a senior fellow at the New America think tank who has engaged North Korean officials at unofficial discussions. And the North has proven slippery before. “At the end of the process, that doesn’t guarantee that they will follow through with that promise. So what I expect is a long, arduous process of talks ahead that will have bumps and setbacks.”