China appears to be growing frustrated with North Korea's behavior, perhaps to the point of changing its long-standing support for Pyongyang. As North Korea's largest economic sponsor, Beijing has provided the North Korean regime with crucial aid for years and offered it diplomatic protection against the United States and other powers. To outsiders, China's alliance with North Korea seems like a Cold War relic with little reason for persisting into the 21st century. However, Beijing's continued support for Pyongyang is not rooted in shared ideology or past cooperation nearly as much as in China's own security calculations. Perhaps nothing sums up the modern relationship more effectively than the oft repeated [...]