A North Korea in transition – whether finally opening up or in collapse, or both – could see mass movements of people.
If Koreans move out of the North they will likely go across the border to China, rather than risk the heavily mined demilitarized zone separating North and South Korea. China has a bit of a window into what that could look like: A flight-to-China scenario actually did happen in the famine years of the 1990s, when, despite the most dire of warnings and penalty of torture or death, tens of thousands of North Koreans escaped to China to avoid starvation.
While there is no similar mass hunger today, China is worried about the lack of control it might have should a war or a crisis force possibly hundreds of thousands of ordinary Koreans across the Yellow River and into its provinces.
The prospect of so many refugees flooding into China would not only be expensive and potentially flare ethnic tensions in the region, it could violate one of China’s prime directives: stability.