I recommend you read George Friedman’s analysis of Chinese policy at RealClearWorld. Note in particular his map of China which highlights factors of which too few Americans are aware, in particular the relatively narrow slice of the country along the coast where its population is concentrated. Here’s a snippet:
In the event there was an economic falling out with the U.S., China had to consider the possibility of a military confrontation. But the key issue was the ability to guarantee China’s access to sea lanes. In this, China had a major geographic problem. The South and East China seas are ringed with small islands, spaced in such a way that passage between them can be blocked with relative ease. The U.S. Navy is far superior to the Chinese navy, and the Chinese were concerned that in some unforeseen crisis the U.S. would block access to their much needed sea lanes. Those small islands were now at the center of Chinese national interest. The Chinese could claim the entire region, but they were not in a position to seize it.
At the same time, the Chinese devised a political solution to their strategic problem. If a country like Indonesia or the Philippines aligned with China instead of with the United States, access to the global sea lanes would be assured without having to confront the United States. The problem here is that the two strategies undermined each other. Aggressive assertion of Chinese power in the regional waters and finding accommodation with regional powers were inconsistent approaches. What’s more, they could only work if the United States was not present. And, of course, it was.
China had one other option for getting around potential U.S. actions: creating an alternative export route through Asia to Europe. This was the One Belt, One Road concept. But it, too, was flawed. First, the cost of building the requisite infrastructure was staggering. Second, it would run through countries that were unstable and, for the Chinese, unimportant customers. Add to that the speed with which One Belt, One Road needed to be enacted, and this was more posturing than policy.
China, therefore, is caught in a set of interlocking problems. Its economic miracle has matured into more normal growth rates. It has a vast population that lacks the ability to consume all that it produces. It has to contend with global stagnation and competition from other producers – and competing with high-tech producers is no small task. It is therefore afraid of internal instability and has imposed a dictatorship designed to maintain a vibrant economy without social costs.
Read the whole thing. These are the sorts of things that I’ve been referring to when I write about China’s internal contradictions and why I’m not overly concerned about China. China has plenty of problems of its own to deal with. The One Child policy has meant that their military is composed largely of only children who are the sole support of their elderly parents. It’s a military much better suited for projecting power internally than externally. The rapid industrial development without adequate civil infrastructure, i.e. political and legal, has resulted in air, soil, and water pollution of resources that are vitally needed. And so on.
But that also explains why the Chinese are inclined to ignore the North Koreans. They have so many problems of their own.