And so they meet again . President Trump and Kim Jong-un, the ruler of North Korea, are expected to gather this week in Hanoi, Vietnam, for a second round of nuclear negotiations. Mr. Kim bested Mr. Trump at their first meeting in Singapore in June last year. And he is poised to do so again.

The reason is simple: He has a strategy and the Americans do not. The United States hopes to somehow keep the world safe from North Korea. But Mr. Kim has an actual plan to make the world safe for North Korea.

Mr. Kim’s plan — the same as his father’s and grandfather’s, and one breathtakingly revisionist — is nothing less than unconditional reunification of the Korean Peninsula under the control of his government in Pyongyang. Nuclear weapons are indispensable to achieving his vision. And rational actors do not bargain away their core interests; only fools or traitors do.

For a time, the Trump team’s counter-proliferation policy — its “maximum pressure” campaign of economic strangulation by way of sanctions — seemed to pose a much more serious threat to Pyongyang’s nuclear quest than did previous American administrations. North Korea’s distorted economy, which is highly dependent on imports of food and energy, as well as foreign subsidies, would not be able to withstand such measures indefinitely, the thinking went. If it was squeezed enough, North Korea’s defense industry would suffer, too, and Mr. Kim’s threat to target the United States would never be fully realized.