Leading article: Kosovo: a triumph for intervention

Today, Kosovo becomes only the third new country of the 21st century. Its declaration of independence will be recognised by a majority of the European Union, including the United Kingdom, and by the United States, but not by Russia. Its birth is more contested and difficult even than that of Montenegro in 2006, which was also detached from an unwilling Serbia, or of East Timor in 2002, which was wrested from Indonesia.

The pessimists have had free run of the Balkans recently, so let us for one day at least join in the celebrations of most of the Kosovar people and reflect on why their statehood is a good thing. Of course, as the nay-sayers point out, Kosovo is a barely viable statelet where life for most of the population is poor nearly a decade after a Nato intervention to "save" them. Unemployment is around 50 per cent; national income per head is little more than £800 a year.

Relations between the ethnic Albanian majority and the tiny Serbian minority that remains are still bitterly hostile, and Serbia refuses to give up its territorial claim. The state will depend for its existence on financial and security support from Nato and the EU for the foreseeable future.

Yet, for all that, Kosovo has been a success of liberal interventionism. Two things are clear. One is that it was absolutely right to stand up to the Serbian nationalism epitomised by Slobodan Milosevic. The most shameful policy of John Major's Government was its appeasement of aggression in the Balkans, standing aside from "ethnic cleansing". The Kosovo war of 1999 finally put an end to all that. As a result, Milosevic fell and Serbia began the long journey to joining the international community.

The other is that it should have been obvious in 1999 that Serbia had lost Kosovo, although it would have been tactless to say it. It has taken a long time for that inevitability to work itself out, but that is no bad thing. The intervening years have allowed adjustments to bruised Serbian pride. In that time, the Serbian people have come to see their future as lying in the European Union, and that pragmatic ambition has brought about, at some level, a grudging acceptance of the facts on the ground.

Only two weeks ago, the Serbians chose Boris Tadic as President in preference to the more nationalist candidate. This may seem a distinction without a difference to outsiders. Mr Tadic sounded uncompromising last week: "I will never give up fighting for Kosovo, and I will, with all my might, fight for Serbia to join the European Union," he said. But the second half of that sentence takes precedence over the first.

Yes, it has been a long time and economic progress has been slow. But that is one of the most important lessons of liberal interventionism, in Kosovo, East Timor, Afghanistan – and even in Iraq, although the disaster of the US-British invasion nearly destroyed the case for interventionism altogether.

Last week, the president of East Timor survived an assassination attempt. Nine years after the Australian-led intervention, its polity too is fragile. In Afghanistan, the support of nations all round the world for the overthrow of the Taliban has not been matched by their willingness to shoulder the burden of nation-building. While US policy may have alienated many countries, it cannot absolve UN and Nato members of their responsibility to the Afghan people for decades to come.

It takes a long time to build the structures of statehood in poor territories torn by conflict. It is expensive and it requires political skill to overcome the inevitable resentment of foreign troops. The difficulties should make us cautious about intervention but, where intervention is justified, they are a challenge to be faced, not an excuse for inaction.

The success of intervention in Kosovo – however qualified and partial – should make us hopeful about such apparently intractable conflicts as those in Darfur and Palestine. But that hope should be restrained by realism and an honest understanding of the long-term commitment required. That means a greater awareness of the geopolitical forces in play over Darfur, for example. George Bush's visit to Africa should make the point that the US is not the obstacle to effective global pressure on the government of Sudan; the main obstacle is China, and the Olympic Games this year provide leverage against Beijing.

Independence for Kosovo, therefore, ought to be welcomed as a step on a long road towards normalisation in a zone of historical conflict, a reminder that human rights can be defended and conflicts slowly mended. Today the members of the EU and of Nato should re-commit themselves to seeing Serbia and Kosovo eventually take their place, side by side and with the other Balkan states, as members of a united, democratic Europe.