This latest nuclear blast, during America’s Labor Day weekend, shows that Pyongyang is less interested in reaping concessions from the international community than in sticking to its playbook of strategic provocations. It seeks maximum political impact by conducting carefully timed weapons tests. The pattern of the United States’ tepid response to these affronts has been to apply incremental sanctions to get Pyongyang to back off a bit and then to defuse tension.

Pyongyang’s provocations, which have been followed by disingenuous talks about denuclearization, have often also won generous blandishments from its adversaries, including at least $10 billion from Seoul and $1.3 billion from Washington over the past 20 years or so. With good reason, Pyongyang sees itself as wielding both a carrot and a stick. Even now, despite solid American support for the South, North Korea is able to pressure Seoul into selective censorship.

Whether North Korea can induce Washington to abandon Seoul or embrace a nuclear North Korea, the security of the rich, risk-averse South will be increasingly compromised either way. The only nonmilitary means of forestalling this ominous trajectory of events is for the United States to enforce both American and United Nations sanctions against the North Korean regime and its enablers, the foremost of which remains China.

Thanks to the strength of the dollar, Washington has the means to create severe financial hardship for Pyongyang. For far too long, the United States has shied away from shutting off the Kim regime’s sources of money and matériel, let alone sanctioning its Chinese partners. This has been out of concern that Pyongyang might escalate its aggression or that Beijing would adopt retaliatory economic measures. These fears are unfounded: North Korea escalates tension according to its own timetable, while China shows restraint in the face of legitimate financial measures.