Anyone who has witnessed the mushrooming disputed-island-chain conflict in the East China Sea knows that China isn't shy about protecting its perceived national interests, no matter how small the stakes. Why then does Beijing appear to tolerate so much bellicosity from North Korea so close to home? As the supplier of nearly half of North Korea's food supply and 90 percent of its energy imports, it seems that Beijing could bring Kim's state to its knees with ease. After all, he has no other allies.

Matt Schiavenza over at the Atlantic sheds some much needed light on this very conundrum:

If China suddenly decided to cut ties to its mercurial neighbor, North Korea would almost certainly collapse. That, precisely, is the point: China really, really doesn't want North Korea to collapse. For one thing, the trickle of North Koreans currently crossing the border would turn into a flood, leaving China with a messy humanitarian situation on its hands. Secondly, a North Korean collapse would no doubt foster the creation of a unified, pro-U.S. Korea on China's northeastern flank, depriving Beijing of a valuable buffer against American interest. For these reasons, China needs North Korea to stay alive— and North Korea knows it.