North Korea spent the pandemic building a huge border wall

FILE PHOTO: Men at a field in North Korea's Sinuiju are seen from Dandong, Liaoning province, China April 20, 2021. Picture taken April 20, 2021. REUTERS/Tingshu Wang/File Photo

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.