SEOUL—North Korea is making a multipronged effort to tackle the threat to regime stability from the rising voice of defectors.

While Kim Jong Un appears to have solidified power smoothly, the regime sees a growing and more-vocal number of defectors as a risk to the young dictator's control. More than 25,000 North Koreans have escaped and settled in South Korea and other countries since the Korean War cease-fire in 1953. Even more are in hiding in China.

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