Looking dazed and despondent, Jang Song-thaek was hauled out by the armpits from a ruling party meeting in Pyongyang by two uniformed guards a few days ago. Jang was the uncle and mentor to Kim Jong-un, a high-ranking official revered in North Korea. His extraordinary and humiliating downfall—North Korean television reported that he was charged with faction-building, drug abuse, womanizing, gambling, and other crimes—stunned observers in South Korea, the US, and beyond. But it is in China that Jang’s dismissal will reverberate most strongly.Jang was a useful and friendly interlocutor between Beijing and Pyongyang. Unlike the young Kim, Jang traveled often to China. He could arrange business deals in North Korea for Chinese businessmen, and he was trusted in Beijing as a responsible monitor of North Korea’s occasionally irresponsible government. He was integral to the China-supported process of setting up special economic zones, where Chinese investors would be treated kindly in the Hermit Kingdom; 14 new zones were set to be opened, North Korean state media announced last month. China was hoping these zones would plant the seeds of economic reform in Pyongyang. Tellingly, among Jang’s charges was “selling resources cheaply,” as the New York Times reports, which Kim had previously complained about and which spurred China, the biggest importer of North Korean ore and minerals, to cancel some of its North Korean resource operations.The true reasons for ousting Jang remain unclear. But in China it is being taken as a bad sign. “He [Jang] is the man China counted on to move the economy in North Korea,” a North Korea specialist told the Times. “This is a very ominous signal.” It will now become even harder for Beijing to rein in its troublesome ally, which to China’s dismay authorized a third nuclear test earlier this year. As the Times notes: “Mr. Cavazos [a former United States Army intelligence officer] said Chinese academics were concerned that Mr. Kim was ‘more and more out of control.’ He added, ‘Every nuclear test by North Korea puts China in a bad position’.”Each time North Korea turns aggressive, confrontational, and unpredictable, the US gets another reason to keep vigilant and well-armed military forces in East Asia, and US allies are happy to leave it that way. That’s the last thing China wants.