For North Koreans, the country’s northern frontier long offered rare access to outside information, trade opportunities, and the best option for those seeking to flee. But as the pandemic gripped the world in 2020, Kim Jong Un’s regime embarked on a massive exercise to seal its borders with China and Russia, cutting off routes plied by smugglers and defectors. Since then, Pyongyang has built hundreds of kilometers of new or upgraded border fences, walls and guard posts, commercial satellite imagery shows, enabling it to tighten the flow of information and goods into the country, keep foreign elements out and its people in. As the pandemic began, North Korea moved to seal its northern borders, tightening control over informal trade routes and making escape harder for defectors. The new security features include additional and upgraded fencing, walls and guard posts along the Yalu and Tumen rivers and in rugged areas such as the revered Mount Paektu. These measures span hundreds of kilometers along North Korea’s borders with China and Russia. New structural changes. The project’s scale is evident in the imagery analysed by Reuters and the US-based Middlebury Institute of International Studies at Monterey, as well as accounts from seven defectors, activists and others familiar with activity along the border. “The traditional North Korea-China route is now effectively over, unless there is a major change in the situation,” said Kim, a South Korean pastor who has helped North Koreans defect. He and others who conduct sensitive work on the border spoke on the condition of partial or full anonymity, citing concerns for their safety and a desire to protect their networks. Only 67 defectors made it to South Korea last year, compared with 1,047 in 2019, official data show. The figure had been declining even before the pandemic due in part to tighter restrictions in China, the preferred route for defectors. North Korea’s government and state media have said little about the construction at the border, and its embassy in London did not answer calls from Reuters. But official North Korean organs have noted increased security to keep out the coronavirus and other “alien things”. In a speech declaring victory over COVID-19 last year, Kim Jong Un ordered officials to “ensure perfection” of an “overall multiple blockade wall in the border, frontline and coast areas and in the seas and air”. The sealing of the border is likely to have lasting effects, including for North Korea’s nascent mercantile class and in the towns where thriving informal trade previously offered many people, particularly women, a chance to make their own way, said Benjamin Katzeff Silberstein, a non-resident fellow at the U.S.-based Stimson Center who researches North Korea’s economy. Those towns “benefited from formal and informal trade since the famine in the 1990s, but really don’t have many other economic advantages,” he said. “So the crackdowns are hitting two vulnerable groups, women and the population of the geographic periphery.” Choking A Lifeline Reuters and Middlebury examined Google Earth Pro satellite imagery of North Korea’s northern frontier, taken at various stages between 2019 and early 2023.