Why does the U.S. government’s foreign policy often hinge on the naïve and moralistic expectation that other countries should act against their own interests? Wouldn’t a more realistic U.S. foreign policy be better for everyone concerned?

Let’s take an example. North Korea is a mostly isolated, totalitarian, unpredictable, and downright weird regime. Its only “friend” in the world is China, which provides fuel and food to prop up a North Korean regime that cannot even feed its people during bumper harvests. With increasingly better relations with a South Korea that has a GDP greater than 30 times that of the North, why does China continue to provide a lifeline for the destitute North?

A New York Times editorial answered this question and then moralized by saying something that the Obama administration would likely agree with:

“China has long enabled North Korea, making clear that its only real concern is stability on its border. But China should realize that an erratic neighbor armed with nuclear weapons is anything but a recipe for stability. . . . After the [North Korean] shelling [of South Korean islands], China called only for a resumption of six-party nuclear talks. It has said nothing about the [newly discovered North Korean nuclear] enrichment plant.”

But if this were the full story, the Times argument would appear logical and valid. Why would China prop up a volatile nuclear power on its border?

When policy seems to defy logic, usually something is missing. In that same day’s newspaper, buried in a regular news story related to China’s reaction to North Korea’s shelling of South Korea and the discovery of the North’s enrichment plant, the Times unearthed something that confounded its own moralizing about China’s shoring up of the nefarious North Korean regime. Times reporters reference and then quote Cai Jian, professor of Korean studies at Fudan University:

“The [Chinese] support continues because China fears that the vacuum created by a sudden collapse [of North Korea] there would open the door to rule by South Korea, ‘and that will put an American military alliance on the doorstep of China.’”

Although never mentioned by the Times, the implicit conclusion is that China’s seemingly irrational propping up of pariah North Korea becomes logical if China fears encirclement by a superpower and its allies practicing neo-containment more than it does a small, erratic nuclear country on its border.

Given these uncomfortable facts, the United States could undermine Chinese support for North Korea by giving South Korea five years notice that it will abrogate the U.S.-South Korean security alliance. This alliance is an anachronism from the early years of the Cold War before South Korea’s economic miracle, when North Korea was backed by both the Soviet Union and communist China. If given time to beef up its military before the U.S. withdraws, the now wealthy South Korea could easily defend itself from the impoverished North. Furthermore, because South Korea refuses to significantly open its markets to U.S. goods, the United States is essentially paying a rich nation to defend it.

Thus, even if North Korea collapsed, the Korean peninsula was reunited, and South Korea ruled the unified country, China would no longer have to fear a U.S. alliance on its border. With this greater threat eliminated, China might very well rather deal with a more rational, wealthy, and stable united Korea, rather than have to prop up an erratic and bellicose North Korea. Thus, the Chinese might very well have an incentive to end assistance to the North—the only thing that keeps the regime from collapsing. Also, a U.S. withdrawal from the South would greatly diminish the possibility that the United States could be embroiled in a brush-fire war over a peninsula that was of questionable strategic value even during the Cold War.

China, South Korea, and the United States could all benefit from the disintegration of North Korea. Thus, everyone—except North Korea—would benefit from a more realistic U.S. policy toward the Koreas.