Leading Article: The strength of democracies fighting a just war

THE THEORY of the just war is not philosophically deep or well- rooted. A new collection of essays by Muslim and Christian authors, The Crescent and the Cross, reveals the extent to which it has been made up to suit the needs of changing times - and to which it has been largely ignored in practice. Two religions born in opposed moral styles - Christianity of turning the other cheek, Islam of conversion by conquest - both ended up forming a remarkably similar theology of the just war. In both cases, the idea of the holy war - the jihad or Crusade - is rejected by mainstream religious teachers. In both cases, the main conditions of a just war are the same. It should be fought only as a last resort in order to right or avert a specific wrong. The good that is done must outweigh the harm of war, and the conduct of the war must itself be just.

Those principles have now been codified in the secular texts of international law, but it is worth recalling their historical sources at a time when an alliance of mainly Christian countries is fighting a war in defence of a largely Muslim group, the Kosovar Albanians.

And it is worth assessing the right of Nato to claim that it is fighting a just war in Yugoslavia, not least because some of the opponents of military action have warned that the West is facing "another Vietnam". The point about Vietnam was that it was not a just war: it was essentially fought against the right of the Vietnamese people to national self-determination. It was doomed because the United States could claim neither the support of the Vietnamese people nor, more importantly, that of the American people. When the US generals claimed that they were fighting with one hand tied behind their backs, the truth was that they should have had both hands tightly bound; the constraints upon them were those of what US public opinion would accept, and they still got away with Agent Orange and the secret bombing of Cambodia.

If the critics mean simply that a war against Serbia in Kosovo could be long and difficult to win, that is not the same as saying that it will be like Vietnam. It is noticeable that very few voices in this country - mainly confined to a small rump of Conservative ultras - argue that the defence of the people of Kosovo against Serbian terror is not a just cause. Morally, the old doctrine that the internal affairs of nation states are inviolate ended with the Holocaust in Germany. So the arguments against Nato intervention that count are those which assert either that air strikes are an immoral means of prosecuting a just war, or that the harm caused by the action outweighs the gain.

The first objection is easier to overcome than the second. All the techniques of modern warfare carry some risk of casualties among non-combatants. This has to be weighed in the balance with the second objection, which is that the Kosovar Albanians are now suffering more than they would have done if the Nato planes had stayed at base. Which might be a strong argument, except that it is conspicuously not being made by the Kosovar Albanians themselves.

All the same, it is incumbent on Nato's leaders now to show that the good that is obtained by this war outweighs the multiple damages and sufferings it has caused, and will cause. Now that the first objective, of deterring Slobodan Milosevic from replacing one population of Kosovo with another, has failed, Nato urgently needs to redefine its war aims.

Here the comparison should be made with the Gulf war of 1991, rather than with the war in Vietnam. Nato's implicit objective now is the liberation of Kosovo, as then it was the liberation of Kuwait; it should be made explicit, and the job will have to be done by troops on the ground, both those of Nato countries and those of the Kosovo Liberation Army, supplied by Nato. The KLA is no one's idea of a human-rights charity, but it is now the means to a just end.

The object is not simply to restore Kosovo to the Kosovars and to protect them. It is to put an end to the ambitions of Milosevic for a Greater Serbia, which is real and frightening, and which depends on an ethnic scorched-earth policy in several areas around Serbia itself.

It is significant that Tony Blair has not ruled out the use of ground troops, and that public opinion both in Britain and in the States is swinging sharply behind their use. This is how just wars in the modern world are fought by democracies whose leaders are open and honest with their people. We need to guard against jingoism, although the press coverage has, in fact, been rather restrained so far. The invention of the monster "Slobba" of Belgrade is a justified use of tabloid techniques to portray a tyrant in vivid colours.

But "Slobba" should beware: democracies are slow to strike but when they do, when they are convinced they are fighting a just war, they strike hard.