North Korea's detonation of its fifth nuclear test last week is a significant punctuation mark in the steadily worsening security situation on the Korean peninsula. The southern half of it, alongside Japan across the water, is faced with the threat of extermination from a 30-something madcap bent on accumulating nuclear weapons with nary a thought for the consequences. His two developed neighbours - who have much more to lose - have desisted from developing nuclear weapons themselves. Riding on that commitment, North Korean dictator by descent Kim Jong Un has pursued his ambitions by cocking a snook at not only Washington, but also his increasingly weary patrons in Beijing, his only ally.

He tilts at South Korea and Japan while his own land is denuded and his people significantly protein-deficient compared with their prosperous cousins down south. The situation would have been laughable were it not for the veritable tinder box it represents. The latest detonation, said to be of an explosive in the 10-kiloton to 30-kiloton range, was at least double that of the previous tests, the last in early January. There is also no knowing how firm his grip is on the levers of power, given the steady stream of executions and "accidents" in Pyongyang involving key people. Instability and insecurity are an incendiary mix and the consequences are unpredictable.

This is why it is important to realise that a pivotal moment has arrived that requires more than muscular shows of B-1 flights over South Korea and threats of more sanctions against the Pyongyang regime. China is partly correct in saying sanctions alone will not solve the issue. But to suggest that it is America's problem is pure buck-passing. The dialogue and consultation China recommends might well be abused, as borne out by past actions of the regime. Beijing must do more to secure peace in the region rather than use North Korea as a foil in its strategic manoeuvres in relation to South Korea and the US. Indeed, South Korea's decision to accept the Thaad missile system, made with some reluctance because of China's obvious alarm at seeing the deterrence balance altered, was a result of Chinese recalcitrance on the matter.

For too long the world has stood around and looked at the North's posturing with scepticism. But the steady accumulation of its nuclear arsenal, and its steadfast advance towards intercontinental ballistic capability, means that the moment has arrived to take the strongman seriously. Sanctions can work, as in Myanmar and Iran where entrenched regimes came to see the light of day because of the pressure so applied. But North Korea, as long as it enjoys a measure of protection from China, is a different matter. So, the ball rests equally on Beijing to help snuff out the fire that its headstrong ally is playing with.