IF THE world sniggered to see Kim Jong Un, with his fat-faced boyishness, thrust forward as the dictator-to-be of North Korea, it is not laughing now. A 65-minute-long artillery barrage on November 23rd rained down upon the tiny South Korean island of Yeonpyeong, marking the first time since the war of 1950-53 that the North has fired shells at civilian targets on land.

Four South Koreans—two civilians and two marines—were killed in the onslaught that left houses and hillsides in flames, and about 20 injured. Yet South Korea's burst of retaliatory fire, which swiftly followed, was also constrained by the danger of escalation—something that it and its allies want to avoid at almost any cost, as the schemers in Pyongyang well know.

After the Cheonan, a South Korean naval vessel, was torpedoed and 46 of its sailors killed, in March, there followed a period of doubt as to who was to blame. Not this time. It was, said Ban Ki-moon, the secretary-general of the United Nations (and a South Korean national), “one of the gravest incidents since the end of the Korean war”.

The barrage came only days after North Korea revealed a new uranium-enrichment facility to American scientists. Its operators told the visitors that its purpose was to generate nuclear fuel—but no one missed the message that its output could just as well be used to make warheads. Only Pyongyang's ruling clique knows what it hopes to achieve by all this, but at least two plausible scenarios could link these two provocations.

The first is that the regime is reverting to familiar gangland tactics to bully its way back to international negotiations under the framework of the stalled six-party talks, chaired by China and including America, Japan and Russia. South Korea and its main allies, America and Japan, have since last year engaged in a process that Barack Obama's administration calls “strategic patience”: offering to renew talks only when the North makes a meaningful commitment to scrap its nuclear arsenal.

Desperate for international aid and recognition, their adversary may be raising the stakes to break their nerve. The regime, after all, knows only too well that without nuclear weapons it will lose its ability to throw its weight around the neighbourhood and scare other countries into giving it help. “They have been pushing and pushing and not getting anywhere,” says Andrew Gilholm of Control Risks, a security consultancy. He reckons this is, in part, their way of saying “you can't ignore us”.

The second scenario is that North Korea wants to show its own citizens that the leader-in-waiting is at least as tough as his father, Kim Jong Il. Victor Cha of the Centre for Strategic and International Studies, and a Bush administration negotiator with North Korea, says the regime has been trying hard to prove its mettle as it enters an unstable era of new leadership.

Whichever hypothesis is right (and both could be), South Korea and its allies find themselves in a difficult position: how do you respond to North Korea without risking escalation? America has reacted by deploying a carrier battle group to join South Korean naval drills in the waters near Yeonpyeong. It is one of several islands within the so-called Northern Limit Line (NLL) that South Korea has claimed as its own ever since the Korean war was ended (technically “suspended”) by armistice in 1953. North Korea, naturally, considers the NLL to be illegal. The naval exercises planned for this weekend aim to deter it from using further bombardments to make that point.

Narushige Michishita, a security expert at the National Graduate Institute of Policy Studies in Tokyo, takes the first scenario further. He says the North's pattern of provocation suggests it is holding out for a peace treaty to replace the old armistice. That is something however that America will not grant unless North Korea makes nuclear concessions first. America's state department insists it will not “buy into this reaction-reward cycle that North Korea seeks to perpetuate”.

This leaves China alone in a position to break the stalemate, by applying quiet pressure on its unruly ally. But China's public reaction, as after the Cheonan's sinking, was to urge calm and to condemn no one. And when China is a milquetoast, it only emboldens the Kim family—making life worse for everyone else.