That remains far harder to answer than the technical questions about Mr. Kim’s bombs and the reach of his missiles that have preoccupied American, Japanese and South Korean intelligence officials for years.
After North Korea’s underground test on Sunday, more is now known about the power of his nuclear arsenal, even if mystery remains about the veracity of the North’s claim that it detonated a hydrogen bomb.
Yet six years after Mr. Kim took power and began executing those who challenged his rule — sometimes with an antiaircraft gun — there is no issue that confounds analysts more than the motives of a 33-year-old dictator whose every move seems one part canny strategy, one part self-preservation, and one part nuclear narcissism.
The conventional wisdom has always been that Mr. Kim, like his father and grandfather before him, is mostly motivated by a deep desire to preserve the family business — a small country that is an improbable, walled-off survivor of Cold War.
Very few people outside of North Korea have met Mr. Kim, including his supposed protectors, the Chinese.
Defectors periodically appear in London or Seoul, and offer insights, but few are true insiders. Documents revealed by Edward J. Snowden show that American intelligence agencies broke into the computer systems of the Reconnaissance General Bureau — the North Korean C.I.A. — but they learned more about operations than intentions.