President Donald Trump’s impulsive decision Thursday afternoon to meet Kim Jong Un was the right call. The upcoming summit will keep the critical alliance with South Korea strong, foil the plans of the dangerous Kim, and put his regime in an exceedingly precarious position. Don’t be surprised if the North Koreans, eventually, do the impossible: surrender their most destructive weapons.

But also don’t be surprised if Trump engineers what the Fletcher School’s Lee Sung-Yoon, in comments to The Daily Beast, said could be “another bleak, embarrassing moment in the annals of inglorious U.S. diplomacy vis-à-vis Pyongyang.”

Thursday evening, Chung Eui-yong, South Korea’s national security advisor, announced to reporters that Trump had accepted Kim’s invitation to a summit. Trump, Chung added, said he would meet “by May.” The New York Times in a headline Saturday called the Trump-Chung get-together “The 45 Minutes That Could Alter History.”

Chung had arrived in Washington that day after meeting with Kim in Pyongyang earlier in the week. The South Korean was not scheduled to see Trump until Friday, but the American leader, hearing that Chung was in the building, invited him to the Oval Office. Trump accepted Kim’s invitation, as conveyed orally by Chung, then and there.

Color Chung stunned by Trump’s immediate “yes.” The South Korean advisor had to call his boss, President Moon Jae-in, in the middle of the night in Seoul to get approval to make the historic announcement on the spot. Apparently, neither Chung nor anyone in the Blue House thought Trump would accept—and make history—so quickly.

No sitting American president has ever met a Kim ruler, and there are many reasons why there has been no such summit. For one thing, every U.S. president has been worried that his handshake would tend to confer legitimacy on what has been, for seven decades, the world’s most horrific regime. Lee calls Kim Jong Un, with ample justification, “the world’s worst tyrant.”

Moreover, given North Korea’s perfect track record of violating every nuclear agreement signed, no U.S. political figure wants to be blamed for making a deal with Pyongyang.

“ No U.S. political figure wants to be blamed for making a deal with Pyongyang. ”

And there is absolutely no appetite in the American capital to hand, what Ankit Panda, writing on this site, correctly calls “a major propaganda coup for the North.”

At the moment, it’s not clear that the North has in fact extended an invitation to Trump to meet. Chung, despite some reporting to the contrary, did not carry an invitation letter from Kim to Trump. All we know is what the South Koreans have been telling us. The North’s state media has remained silent on both the offer to Trump and his acceptance.

Yet whether the invitation is real or not, there were nonetheless powerful reasons for Trump to agree to meet with Kim. The most important one? South Korean President Moon wanted him to do that.

Many analysts in the last few days have pointed out all the “traps” in Trump meeting Kim, but they have ignored the biggest trap of them all: what might happen if the American president refused to do so. Refusing to meet would have driven a wedge between South Korea and the U.S., and I suspect that if there is any reason why Kim made his bold overture, it was to have it turned down.

Kim and his predecessors, his dad and granddad, have had one overriding goal, the takeover of South Korea. The United States, in their view, is the one obstacle to achieving that objective.

The U.S. has many reasons to keep South Korea independent. First, for about a century and a half Washington has drawn America’s western defense perimeter not off the shores of Hawaii but off the coast of the Eurasian landmass. South Korea anchors the northern end of that perimeter.

Second, an absorption of South Korea by its northern neighbor, Beijing’s only formal military ally, would strengthen China’s grip on East Asia, and American policy has been to prevent any one power from dominating that region.

Third, with Xi Jinping’s China stepping up its attacks on the concept of representative governance, Washington cannot allow any dictatorship, especially one so closely linked to Beijing, to kill off any democracy.

Given the importance of South Korea to America, maintenance of the U.S.-South Korea mutual defense treaty is crucial to Washington. Moon is, in general outlook, anti-American, so at the moment the most important American imperative on the peninsula is to keep him from gutting the alliance. Yes, Moon in public says things American policymakers want to hear, but he’s gritting teeth when he does so. And he acts in ways incompatible with being an alliance partner.

The overriding reality is that the United States and alliance partner South Korea are together stronger than North Korea and its partner, China. As long as Washington and Seoul stick together, there will almost certainly be acceptable outcomes—and perhaps even good ones—on the Korean peninsula. None of Kim’s objectives, whatever they are now or will be in the future, can be achieved if Washington and Seoul stand together.

So what is the Kimster now up to?

Kim almost certainly needs relief from sanctions that appear to be crippling his regime.

Moreover, David Maxwell, who served five tours in South Korea as a U.S. Army officer, thinks Kim may be setting up Moon by making him “the middleman” in talks. “Kim may think that by allowing the South to have a diplomatic ‘win’ he can extort an even greater amount of money from President Moon,” Maxwell tells The Daily Beast. Also, Kim may be trying to get Moon to assume a role that will one day put South Korea into opposition to the United States.

At least up to now, that plan has not worked.

So where does Kim go from here? As Robert Collins, who has worked extensively with U.S. Forces Korea, e-mailed The Daily Beast, “Kim’s strategists are well known for their own ‘art of the deal.’”

“ Maintenance of the U.S.-South Korea mutual defense treaty is crucial to Washington. ”

And Kim deal artistry is not that hard to figure out if you’re a historian. As Fletcher’s Lee, a historian, points out, Kim Jong Un is now taking a page from his father’s playbook, from the year 2000.

That year, Kim Jong Il, Kim Jong Un’s father, met in Pyongyang with South Korean President Kim Dae-jung in June and then tried to meet President Clinton in the following months. Kim in October sent Vice Marshall Jo Myong Rok, the second-in-command of his army, to the Oval Office to prepare for the Clinton visit. Secretary of State Madeleine Albright went to the North Korean capital two weeks after that to finalize preparations, but the administration ran out of time. There was no Clinton-Kim summit.

Lee now thinks that this time Kim Jong Un, duplicating his father’s tactics, might propose sending “First Sister” Kim Yo Jong, who took South Korea by storm last month at the Olympics, to D.C. to win hearts and minds.

Many will object to Ms. Kim coming to Washington—she may have as much blood on her hands as her brother—but Trump has already decided to meet with her brother, Killer Kim. And that was the right call because the imperative now is not to give Moon any excuse to side with North Korea against America.

If the South Korean president gangs up with the other Korea on Washington, then Trump is on his own and under pressure to make another appalling nuclear deal with the Kim regime.

At this time, only one thing is certain. Kim Jong Un will never stop trying to divide Seoul and Washington. For Trump’s Washington, the goal is clear: keep the alliance intact and the sanctions air-tight so that the Pyongyang regime will one day have no choice but to bend in the face of unrelenting pressure.

And who knows, Trump may be able to make the historic summit a “propaganda coup” for America.