Qing in the North
An article by the South China Morning Post reported that recent analysis by a team of researchers at the University of Science and Technology of China in Hefei postulated another underground nuclear explosion at the North Korean Punggye-ri test site may cause the collapse of the mountain that is on top of the test site. Such a collapse could possible create a cloud of radioactive debris settling across the region, posing danger to Koreans, Japanese, Russians, and, most pertinently, Chinese.
Environmental catastrophe and China are the peanut-butter-and-chocolate of industrial hubris. Beijing's struggle with smog and bacterial blooms strangling marine life in waterways are a peek into America's past and possible future. But China has been able to avoid widespread nuclear contamination in its quest to modernize, and that is no small feat - Chernobyl, Three Mile Island, and Fukushima are all cautionary tales with different lessons. The Hefei team's analysis may portend another lesson to be learned, but what lesson that is will depend on what geopolitical steps are taken.
It is very possible that the analysis was a purely scientific endeavor. But regardless of its intention, its findings can serve as a casus belli for the Chinese government to intervene in the unfolding Korean drama - North Korea recently claimed to have developed a thermonuclear weapon, and the claimed test may have been accompanied by a cave-in at the test site. The analysis by the Hefei team serves as a non-official warning to the North Korean government - their nuclear testing is already putting Chinese interests in danger. Now it may be putting Chinese lives in danger. If there is another underground nuclear test - at least, at the Punggye-ri test site - this can be interpreted as reason enough to turn their back on their fellow nominal communists.
Assuming that North Korea will test additional nuclear weapons, this gives them a few options. They could try and find another suitable underground test site, but that is easier said than done. Alternatives are an ground-level detonation, an underwater detonation, an airburst detonation, and a detonation in the vacuum of space - all of which spreads some level of radiation out of North Korea, all of which makes their nuclear capacity easier to observe, and all of which serves as a stark image of danger. Such a public display of nuclear capability may frighten North Korea's opponents into submission - it could also serve as a rallying point for forceful foreign intervention.
China has three primary concerns to keep in mind - it wants to stay open for business with the United States, it wants to expand and entrench its economic and political relationships with other Asian nations, and it wants to restrict America's capacity to attack China. That last part is why it supports North Korea as a buffer to America's military presence in South Korea, and why it has shielded the North Korea regime's quest for nuclear weapons. Events are beginning to unfold in Korea where it may harm business with America and permanently drive South Korea (and, through war, possibly the entire Korean Peninsula) into the American fold - the resurrection of SEATO (think an Asian NATO) with America at the helm is China's worst nightmare. War is bad for business, and the prospect of having to deal with hundreds of thousands of uneducated, unhealthy and unhappy war refugees from North Korea is a system shock China would rather not deal with.
But in times of crisis, the amount of good ideas is restricted, and one has to start looking for the least bad decision. President Donald Trump's threat to cut off trade with China was off-the-cuff and not realistic, but it did serve as a wake-up call of sorts for the Chinese. One way or the other, trade with the United States will be harmed - not with a full-spectrum embargo, but with incremental tariffs and investment restrictions. Both sides lose in a trade war, but China stands to lose more - all countries' stability is predicated to some extent on maintaining quality of life for its civilians, but this is more of the case with China than with America. America has a tradition of rule of law underpinning its society that China, despite its Confucian heritage, cannot match. Income inequality, corruption, ethnic cleansing, and regionalism are all dangers to the control the Communist Party has on China, and war in Korea poses a danger to the stability that ensures control.
It is thus in China's interest to prevent war. And the threat of Chinese intervention in North Korea - be it oil being cut off or the PLA crossing the Yalu river - may be what prevents it. To do this, China needs a credible reason to turn its back on a long-time ally - saving face is a legitimate diplomatic concern, and most crises are diffused when both sides can save face and claim victory, be it moral or measurable. The prospect of a unified worldwide Communist front was broken with the Sino-Soviet split; a Sino-Korean split would need to be for a damned good reason if the Communist Party of China is to retain its facade of actually being communist. Being directly responsible for irradiating Chinese citizens via nuclear test after being warned by a Chinese university not to do a nuclear test would be the casus belli they need to end their relationship.
All of this is predicated on the future actions of Kim Jung Un, who would certainly lose any open conflict with either China or the United States. His reign is ensured by the threat of war more than his capacity to win it, which he knows. But wars can happen by accident as much as they can happen by design, and a chain of escalations - be it to better position for war, or to save face - can kick off a war that nobody truly wants. But if and when war does occur, nations fight not only for the current war, but for the future wars - and this principle is why the threat of China invading North Korea is credible. Because while North Korea as an entity may be worthwhile to China, Kim Jung Un is not. A Chinese excursion to set up a puppet state in North Korea may actually receive international approval if it means bringing their nuclear weapons underneath the more predictable arsenal of China.
It takes a clairvoyant to see the future. Analysts can not claim to do so. What they can claim to do is to see a possibility, and explain how probable it is. China invading North Korea was always a possibility - the warning out of Hefei is a sign of this possibility being more probable rather than less. And with South Korean ministers openly inquiring about placing American tactical nukes on the peninsula, the schedule of war may be moving up.