As tensions grow between the U.S. and North Korea, onlookers have increasingly called on China to intervene. Which makes sense. Beijing is Pyongyang’s biggest trade partner and the two countries have a relationship that stretches back to World War II. But just because China is North Korea’s closest ally doesn’t mean China has control.

According to Chinese history expert Adam Cathcart, China’s relationship with the DPRK is complicated. Cathcart lectures about China and Chinese history at Leeds University in Britain and he’s spent some time along China’s border with North Korea. This week on War College, he explains the relationship between the two countries, what the border looks like and what happens Chinese border guards interrogate you.

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(Produced by Bethel Habte)