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North Korea is a difficult place to spread the Gospel. In the last year, at least three Christian activists working on the border have been stabbed by poisoned needles, likely wielded by North Korean assassins; one, a South Korean pastor who helped smuggle North Koreans out of China, died by the time he reached the hospital. Dozens of missionaries have languished in Chinese prisons, arrested after leaving North Korea or while attempting to enter.

Despite the perception of North Korea as a country hermetically sealed to the outside -- and despite the very real risks -- dozens, if not hundreds, of Christian missionaries operate inside the country, sometimes living there for months at a stretch, in the capital, Pyongyang, or in the Rason region, near the country's...