By Eric Vandenbroeck

No country in history has spent such a large share of its wealth on nuclear weapons. North Korea is thought to have a stockpile of around 20 devices. Every six weeks or so it adds another. And we can presume that if attacked by the US, although there are limits to these weapons' effectiveness, N. Korea would counter strike using its considerable artillery, rocket and missile arsenal. But would if this would be enough to dissuade the United States is another question.

An underground nuclear detonation in January, claimed by the regime to be an H-bomb (but more likely a souped-up A-bomb), has been followed by tests of the technologies behind nuclear-armed missiles. Although three tests of a 4,000-kilometer (2,500-mile) missile failed in April, North Korean engineers learn from their mistakes. Few would bet against them succeeding in the end.

North Korea is not bound by any global rules. Its hereditary dictator, Kim Jong Un, imposes forced labor on hundreds of thousands of his people in the gulag, including whole families, without trial or hope of release. Mr Kim frequently threatens to drench Seoul, the South’s capital, in “a sea of fire”. Nuclear weapons are central to his regime’s identity and survival.

Deterrence is based on the belief that states act rationally. But Mr Kim is so opaque and so little is known about how decisions come about in the capital, Pyongyang, that deterring North Korea is fraught with difficulty. Were his regime on the point of collapse, who is to say whether Mr Kim would pull down the temple by unleashing a nuclear attack?

The mix of unpredictability, ruthlessness and fragility frustrates policy making towards Mr Kim. Many outsiders want to force him to behave better. In March, following the recent weapons test, the UN Security Council strengthened sanctions. China is infuriated by Mr Kim’s taunts and provocations (it did not even know about the nuclear test until after it had happened). It agreed to tougher measures, including limiting financial transactions and searching vessels for contraband.

But China does not want to overthrow Mr Kim. It worries that the collapse of a regime on its north-eastern border would create a flood of refugees and eliminate the buffer protecting it from American troops stationed in South Korea. About 90% of North Korea’s trade, worth about $6 billion a year, is with China. It will continue to import North Korean coal and iron ore (and send back fuel oil, food and consumer goods) as long as the money is not spent on military activities—an unenforceable condition.

Protected by China, Mr Kim can pursue his nuclear program with impunity. The sanctions are unlikely to stop him. If anything, they may spur him to strengthen and upgrade his arsenal before China adopts harsher ones.

Can anything stop Mr Kim? Perhaps he will decide to shelve his “nukes first” policy in favor of Chinese-style economic reform and rapprochement with South Korea. It is a nice idea, and Mr Kim has shown some interest in economic development. But nothing suggests he would barter his nuclear weapons to give his people a better life.

Perhaps dissent over Mr Kim’s rule among the North Korean elite will lead to a palace coup. A successor might be ready for an Iran-type deal to boost his standing both at home and abroad. That is a possibility, but Mr Kim has so far shown himself able to crush any challengers to his dominance.

The last hope is that tougher sanctions will contribute to the collapse of the regime—which, in turn, could lead to reunification with the South and denuclearization of the Korean peninsula. That would be the best outcome, but it is also the one that carries the most danger. Moreover, it is precisely the situation China seeks to avoid.