Asia has gone nuts for nukes this week. On the heels of a Pentagon report that China is loading multiple warheads onto its intercontinental missiles, North Korea announced Wednesday that it has developed warheads of its own, making the transition from a nuclear-capable power to a nuclear-loaded one.

The North Koreans may be lying or exaggerating, of course. But even so, the announcement augurs a new stage in the complex relationship between China and North Korea. China regards the north as an unruly client state, annoying in practice but necessary as a buffer between the U.S. forces stationed in South Korea. Now, apparently, China may be prepared to treat North Korea as an actual nuclear proxy, strengthening Beijing’s regional position by counterbalancing America’s allies in Seoul.

The difference between an irritating ally and a valued proxy can be difficult to discern, so let’s start there. Since China began its transformation from communism to a unique brand of state-directed and state-owned capitalism, North Korea has increasingly become an irritant. Ideologically, North Korea is hidebound, a reminder of the bad old days of personality cults and mind control. Economically, it’s a disaster zone ― and needs a steady flow of food and other aid to keep its citizens from starvation.

But from China’s perspective, what’s worse than the archaic politics is North Korea’s crazy-seeming attitude of confrontation with South Korea. Repeatedly, North Korean provocation has brought the countries dangerously close to conflict. A war between them would be a disaster for trade ― China’s main concern for the last 25 years.

Throughout China’s peaceful rise, North Korea’s confrontationalism was also bad for the image Beijing was trying to project. Protecting a belligerent regime made China seem belligerent by association, risking Western distrust that could have spilled over into economic relations.

Still, Chinese leaders realized they were stuck with North Korea for geostrategic reasons. If the north collapsed, and was swallowed into South Korea, then U.S troops could have been stationed on the banks of Yalu River ― unacceptable proximity from the Chinese point of view. So the Chinese approach was to whisper or hint to the West that North Korea was like an unruly child, and couldn’t be completely controlled. By implication, China was communicating that it wished the North Koreans would behave reasonably ― like the Chinese themselves.

For North Korea to boast that it had developed missile-capable warheads would have been unacceptable to China’s leaders during that period of annoyed tolerance. The North Koreans don’t run every key announcement by Beijing; but they’re sophisticated enough to know that their actions will have consequences, and they always anticipate Chinese reaction. In the past, China would almost certainly have felt the need to pressure North Korea to back down from such a claim ― much as China participated in years of multilateral talks aimed to stop North Korea from becoming a full-fledged nuclear power.

This week’s events show how starkly circumstances have shifted. The North Koreans apparently judged that, a few days after China’s MIRVs made headlines, Beijing’s leaders would be in no position to chide them for publicizing their own nuclear strength.

North Korea clearly interpreted China’s aggressive announcement of multiple warheads as a sign that China wants to project itself as a militaristic regional and global power. The reason, the North Koreans know, is in part to respond to a slowly emerging U.S. containment strategy that involves strengthening the military capacities of America’s Pacific allies such as Japan and South Korea. While Washington insists its goal is simply to ensure free passage throughout the region’s economically vital sea lanes, China is feeling boxed in.

In this changed ― and charged ― “cool war” environment, China no longer sees North Korea’s belligerence as an irritant. Instead, it looks like a useful tool. With the U.S. encouraging Japan to give up its constitutionally mandated pacifism, China can now look on with approval, or at least without disapproval, while North Korea brags of weapons that can target not only South Korea but also Japan.

If so, the Chinese need not have approved North Korea’s move in advance, or have abandoned their concerns about a super-charged, hypersensitive, aggressive North Korea. It’s enough that China will realize the benefits of North Korea’s move ― and will refrain from chastisement. Strategic logic will do the rest.

A good theory ― and my interpretation is certainly a theory ― should be falsifiable. This one is. If China now takes identifiable steps to rein in North Korea’s claims or otherwise signal its displeasure, then I ― and perhaps the North Koreans, too ― will have miscalculated.

But if China makes no move to distance itself or to criticize North Korea’s announcement, even implicitly, that’ll be a strong indication that a new Beijing-Pyongyang relationship is emerging. A global power confronting another global power needs proxies, as the U.S. and the Soviet Union showed during the Cold War. North Korea was once such a proxy ― and it may be again.

By Noah Feldman

Noah Feldman, a Bloomberg View columnist, is a professor of constitutional and international law at Harvard University and the author of six books, most recently “Cool War: The Future of Global Competition.” ― Ed.

(Bloomberg)