The story of how a line on a map becomes a hard state border that no one can cross. Korea was ruled as one Kingdom for a thousand years. They valued poetry and scholars helped rule the country. But their Kingdom was invaded by Japan. When Japan left, Russia and America raced to take their place. Amid frantic organising, a line dividing Korea in two was suggested. Who knew that line would become the front line in a war, eventually creating a hard border between two new countries?

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(image 2018: A North Korean student attends a class at Kang Pan Sok revolutionary school outside of Pyongyang. Credit: Ed Jones/Getty Images)