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, revered in North Korea. His extraordinary and humiliating downfall stunned observers in South Korea, the US, and beyond. But it is in China that Jang’s dismissal will reverberate most strongly.