BIRDS OF A FEATHER: The spark with South Korea is gone as China makes clear the North comes first.

The degree of warmth between Ms. Park and Mr. Xi was unexpected, given that South Korea is a staunch American ally and China is North Korea’s socialist bedfellow. But they had a mutual interest in cozying up.

Mr. Xi sought to drive a wedge between Seoul and Washington. He also wanted to further poison Ms. Park on Japanese Prime Minister Shinzo Abe, who early in his tenure had enraged the two countries by visiting the Yasukuni war shrine, where Japanese war criminals are honored.

For her part, Ms. Park invested heavily in the relationship in hopes that it would encourage Beijing to do more to restrain Pyongyang’s nuclear ambitions.

She’s still waiting for the payoff. Judging by North Korea’s latest nuclear test, its fifth, it may never come.

The mistake Park made was forgetting that for dictatorial regimes, international commercial interests, no matter how lucrative, will inevitably take second place to domestic political exigencies, no matter how transitory.