The news from North Korea is usually nasty and bizarre, especially in the three years since Kim Jong-un inherited the insidious personality cult of his grandfather and father. The 30-something Mr. Kim was said to have fed his disgraced and once-powerful uncle to a pack of dogs for disrespecting him. His latest action, as initially reported by South Korea’s National Intelligence Service, was to have the minister of the armed forces blasted to pieces with an antiaircraft gun, purportedly, among other things, for dozing off while Mr. Kim spoke.

The uncle, Jang Song-thaek, was indeed executed, but the dog story turned out to be the creation of a satirical Chinese blog. And South Korea is now saying that Gen. Hyon Yong-chol was purged, not provably killed. That the more lurid versions do not always hold up doesn’t change the fact that Mr. Kim has been purging the top ranks of his regime at a lively clip since he came to power in 2011 — at least 70 senior officials have been killed, according to South Korea. The Kim dynasty, as a United Nations panel reported last year, has committed systematic crimes against humanity, including executions, torture, rape, deliberate starvation and almost total suppression of free thought.

Why Mr. Kim is doing this is a matter of considerable conjecture. One explanation is that he is unstable and threatened, and so needs to fuel the terror that his power rests on. The simpler explanation is that this is simply the way the Kim dynasty does things. There is no way to know for sure.

When the “Great Leader” Kim Il-sung, the founder of the dynasty, died in 1994, there were widespread expectations that the regime would collapse. But he was posthumously promoted to “eternal president” as his son, the “Dear Leader” Kim Jong-il, carried on, presiding over the incarceration of 200,000 political prisoners and a terrible famine.