If demography is destiny, in North Korea the guiding force is ancestry. Like his grandfather and father before him, Kim Jong-un suffers delusions of grandeur, surrounded only by frightened sycophants, coveting a place among the world's important nations. As Pyongyang edges closer to building a working nuclear missile capable of reaching the United States, Mr. Kim must get the right response to his vow to annihilate his enemies. Tough talk from the United States and its allies is only a stopgap. The solution, short of war, lies with China.