The nuclear test announced by North Korea yesterday, and subsequently verified, has ended three years of international uncertainty and unleashed a predictable furore. Pyongyang has taken to its logical conclusion the defiance it registered when it walked out of the Nuclear Non-Proliferation Treaty three years ago. If Kim Jong Il's hermit kingdom was not already a pariah state, it certainly qualifies as one now.
And, as a succession of national leaders made clear yesterday, there is a host of reasons for grave concern. North Korea is a totalitarian state; it is closed to the outside world and its regime is believed to be fragile. Its ruler, Kim Jong Il, has chosen to spend what resources his country has on developing a nuclear weapon, rather than improving the welfare of his people - who would be on the brink of starvation, were it not for food aid from, among others, the United States.
None of this contributes to stability, not in the world at large, nor - more particularly - in the immediate region. South Korea, Japan and China, and to a lesser extent Russia and the United States, are justified in their alarm. It is scant consolation that North Korea has so far proved incapable of firing a weapon-bearing missile with any accuracy. If Pyongyang has been persistent enough to explode a nuclear device, it could one day test an effective missile.
Yet the West, and the US in particular, must take some responsibility for this turn of events. This is not because, as some have claimed, of any provocation the Iraq war might represent - this is not a concern to Pyongyang. It is because we paid too little attention to North Korea and showed lamentable inconsistencies in our policy. Overtures begun by Bill Clinton towards the end of his presidency were halted by his successor, George Bush. Thereafter, too little effort was made to distinguish North Korea's fears from its aspirations, boasts and open blackmail. Nuclear threats eventually produced food aid: what conclusion was Kim Jong Il to draw?
Now that Pyongyang has alerted the world to the danger it could present, however, cool heads and calm judgements are in order. This latest development is only as destabilising as we allow it to be. Potentially, it could alter the balance of power in North-east Asia. But it does not mean that North Korea is about to declare war on anyone; it has stressed the defensive purpose of its new lethal weapon.
Nor is this necessarily the end of the Nuclear Non-Proliferation Treaty - although the prospect of a nuclear arms race accelerating in North-east Asia is a threat that cannot be ignored. Until now, the almost 40 year old treaty has stood the test of time remarkably well and, as Iran's difficulties show, acquiring a nuclear capacity of any kind is far from simple. Regionally, South Korea already enjoys the protection of the United States, as - less publicly - does Japan. China is already a nuclear power. In the longer term, though, Japan could reconsider its non-nuclear status. The country's new prime minister, Shinzo Abe, has promised a more assertive foreign and defence policy. As his visit to Beijing has just shown, however, he also favours a rapprochement with China that could be of great benefit in diplomacy with North Korea.
For all the strong words voiced yesterday, diplomacy is still the only realistic course. With the six-party talks, a mechanism is in place, and the UN is already involved. A ban on North Korea's export of nuclear materials and expertise would be a sensible first measure. If North Korea is intent on making itself into a nuclear-armed fortress, it can hardly complain if it is treated as one. This is no reason, though, why the talking should stop. Indeed, it is more necessary than ever.