Last night, President Donald Trump did what no other sitting U.S. president has done—he stepped foot onto North Korean soil and greeted North Korean chairman Kim Jong-un. And in typical Trump fashion, he staged a second dramatic crossing over the military demarcation line at Panmunjom with Kim, stepping together onto South Korean soil and greeting South Korean President Moon Jae-in before having a fifty-minute meeting in the South's Freedom House.

Leaving the DMZ, Trump said, "We moved mountains," and that working-level talks led by U.S. special representative Stephen Biegun would get started right away. "The meeting was a very good one, very strong . . . We're not looking for speed, we're looking to get it right."

To get it right, the first step the Trump administration should take is to offer North Korea a security guarantee, whether in the form of an end of war declaration or a non-aggression pact. It may have been, after all, what convinced Kim to meet Trump at Panmunjom.