Over the past year, the People’s Republic of China (PRC) has managed to antagonize virtually all of its maritime neighbors as ongoing disputes over territorial claims, oceanic borders, and maritime rights have boiled over. None are as potentially dangerous, however, as that between China and Japan, which are becoming ever more committed to their respective claims over the Senkaku Islands.

The U.S. commitment to its security treaty with Japan means it is potentially our problem, too.

The situation gained new prominence this past April when, during a speech at The Heritage Foundation on behalf of the Tokyo Metropolitan Government, Governor Shintaro Ishihara offered to buy the islets from their private owners. The Japanese national government chose to defuse Chinese protests over the governor’s move by buying them instead. From Beijing’s perspective, however, Japan’s “nationalization” of the islands (as the Chinese have taken to calling it) did not dampen the problem but exacerbated it.

That Beijing’s conduct in 2010, when it chose to curtail exports of rare earths over this issue, has alienated much of the region toward the PRC appears utterly lost on the Chinese leadership. Similarly, the Chinese appear to be ignoring the impact of Chinese attacks on Japanese firms and diplomatic facilities on regional perceptions of them as both trading partner and potential threat. The attacks on owners of Japanese cars, and not simply Japanese facilities, highlights the potential for sanctioned and facilitated nationalist demonstrations to metastasize.

Nonetheless, one way the PRC has avoided inflaming the issue is by not defining the precise boundaries of several of the disputes and keeping its navy out of the mix. But this past week, it shifted its stance.

Beijing has now issued a definition of the boundaries of the Senkakus and dispatched additional government ships to enforce it. While these ships have been drawn from various civilian, law-enforcement-type agencies (of which there is a myriad, rather bewildering array), some of them are armed. These vessels, in turn, have tried to expel Japanese ships from the area, including Japanese coast guard vessels.

While the situation has not come to blows, it is clear that tensions are rising, as is the potential for escalation. In particular, it is worrisome that Chinese warnings and escalatory behavior would seem consistent with the potential of introducing military elements into the equation, forcing other states to assess whether they want to escalate (by bringing in their own military forces) or whether they should concede the territories.

In effect, the Chinese appear intent on placing the onus of the “last move” (to borrow from Thomas Schelling’s writings on deterrence), and avoiding catastrophe, on their adversaries—here, the Japanese.

Meanwhile, former Chinese ambassador to Japan Chen Jian has now openly accused the United States of fomenting the crisis: “It is in the U.S. interest to quarrel with China, but not to fight with China.” Chen’s remarks imply that Beijing sees the U.S., and not Japan, as the main factor in the Senkaku crisis.

For the United States, this has serious implications, since the U.S. has underscored that the U.S.–Japan mutual defense treaty applies to the Senkakus, as they are under the “administrative control” of Japan. Chen’s statement suggests that the Chinese are testing American resolve and the limits to its treaty commitments. Does the U.S. stand up to the Chinese on behalf of its legal commitments to Japan, or does it, as it did in the case of the Philippines this summer, force its ally into accommodation?

The Chinese are likely banking on the latter. If they are right, there is little reason to expect them to step back, and regional security and peace will face a growing threat from an ever more nationalist PRC.