Just last month, Vice President Mike Pence toed the hard line against North Korea. During the opening ceremony of the Winter Olympics in South Korea, he refused to stand when the joint Korean team entered. He ignored the presence of Kim Yo-jong, the sister of the Kim Jong Un, the North Korean leader. She sat 10 feet away. Pence reflected the Trump White House strategy of “maximum pressure.”

On Thursday evening, all of that seemed to change, suddenly and unexpectedly. President Trump accepted the invitation of Kim to sit down and talk. That isn’t to say the pressure will ease, most notably in the form of economic sanctions. The acceptance does go to the diplomacy that has been sorely missing.

The past year, the two leaders have engaged in what amounts to an exchange of insults and taunts, unnerving many in view of North Korea leaping ahead in its development of nuclear weapons. Would the two stumble into conflict? In that way, the prospect of meeting and negotiating represents a favorable turn.

What changed? More than anything, President Moon Jae-in of South Korea has pushed an agenda of outreach to North Korea. With the new year, Kim Jong Un has reciprocated, starting with the joint Olympic team and a series of productive conversations.

Kim recently told South Korean officials that he would talk with the United States about the future of his country’s nuclear program. He added that during the talks, he would suspend nuclear missile tests and register no objection to the United States and South Korea conducting military exercises. That is an overture worth exploring, especially when South Korean officials carry the Kim invitation to the White House.

Exploration takes many forms. In jumping to an early meeting with Kim, the president has departed from convention. What deserve calibration are the expectations. Both leaders have proved impulsive and brash. Add the long animosity between the two countries, and there is a good chance the meeting will not take place.

If it does go forward, this isn’t something an ill-prepared and ill-informed President Trump can improvise. Kim and North Korean officials fulfill an ambition in just meeting, their brutal regime on a par with the American side. What will Washington get in return?

Hard to imagine ever seeing North Korea give up its nuclear weapons, let alone in one meeting. Progress, realistically speaking, would be establishing a diplomatic presence in each country, or a framework for future talks or a pledge to halt missile tests and enrichment. If the way the meeting has emerged is unconventional, little has changed about how relations are built and sustained. That takes knowledge, understanding, diligence and political skill.

President Trump isn’t doing this alone. He must bring along Japan, China and Russia, all while coordinating with South Korea. There are many scenarios for this gambit falling apart. What is encouraging to see is diplomacy entering the scene, negotiation more productive than bluster.