Ever so carefully, Mr Blair clears the way for a ground invasion

The rule book of global realpolitik is becoming obsolete in relation to the present conflict

ACCORDING TO one theory, the indictment of Slobodan Milosevic at the international war crimes tribunal in The Hague is a disaster, for which the British Government is especially, if not uniquely, to blame. Apart from the unpredictable effect on the psychology of the Serbian leader, it creates difficulties, possibly terminal ones, for the diplomatic process.

If immunity from prosecution is one of Milosevic's demands, then it is now much less easy to grant. By being outlawed, Milosevic has less incentive to make peace. There could be no new Dayton, since Milosevic could not travel outside Serbia without being arrested. And while there is nothing to prevent foreign politicians or diplomats - Russian, Finnish or any other - from visiting Milosevic as an indicted but unconvicted leader, in Belgrade itself it cannot fail to undermine, in the eyes of the Serbian regime, the bankability of the peacemakers' proclamations of good faith.

Sensible of the independence of the tribunal, the Government did not, in fact, force - and indeed could not have forced - the tribunal to indict Milosevic. But it has regularly supplied the prosecutors in The Hague with evidence, including intelligence reports, against the Serbian leader and, despite Robin Cook's judicious public comments yesterday, it can hardly be less than gratified that he has now been indicted.

It is precisely this response, it will be claimed sotto voce in several European capitals over the next few days, that is so misguided. For the indictment, we will be told, is high up the list of avoidable errors in the rule book of global realpolitik.

There is, however, a telling objection to this theory, which is that the rule book itself is becoming obsolete, at least in relation to the present conflict. The agreement on the dispatch of another 21,000 troops to the region is a profound development, aptly described by Paddy Ashdown this week as changing the meaning of the phrase "keeping all the options open" from that of a simple choice between more bombing and compromise, to one that includes the use of land forces to make peace as well as keep it. It has changed the boundaries of the possible, and perhaps the probable. It raises, at last, the real prospect of ground forces entering Kosovo in advance of a deal. The agreement of Milosevic, under pressure of bombing alone, to make peace is no longer the essential precondition of Nato's entry into Kosovo. And if the negotiation of a settlement is no longer as essential as it once was, then it follows that the Allies can afford to be more cavalier about the obstacles to diplomacy.

Not all of Nato will see it like that, of course. It was apparent during Robin Cook's shuttle through Rome, Bonn and Paris this week that more hopes are expressed in those capitals for the diplomatic efforts of the Russians than in London, where there is little or no sign of optimism about their success. In not one of those countries, moreover, are ministers prepared to go even as far as the British in admitting publicly the possibility of entry into Kosovo before a deal with Milosevic. The easy conclusion, therefore, is that Britain and, on its increasingly frequent good days, the United States, are still standing dangerously alone in being ready to enter Kosovo in circumstances in which there is still some risk of resistance.

That underestimates, I suspect, the subtleties of what is happening in Europe. Take one example of the widespread assumption that the leading Nato countries in Europe are hopelessly split. Thanks to the detective work of the Labour MP Denis MacShane, we now know that Chancellor Schroder did not say last week in Bari that Nato entry short of a deal was "unthinkable"; he suggested, rather, that the Germans, at least, were not considering such an operation themselves. Nothing the German Foreign Minister Joschka Fischer said to Mr Cook this week contradicted the growing impression that the Germans are not prepared to enter Kosovo before a signed deal, but that they will not argue against other Nato countries doing so.

However, it also underestimates the intensity of the painstaking diplomatic effort now being conducted in Europe, principally by the British Government, to prevent the Alliance crumbling at the edges. Mr Cook enjoys his job but he did not go to three capitals in one day for fun, or even for domestic consumption. He was rewarded by a series of declarations embodying the highest common factor, rather than the lowest common denominator, of agreement. No one, including the Italians, ruled out the possibility of entry in "non-permissive" circumstances, each of Mr Cook's counterparts saying instead that it was "hypothetical". Each one also pointed publicly to the dangers of "leaving a vacuum" in Kosovo as the Serbian grip on the territory is loosened. This, of course, appeals to those who worry about the Kosovo Liberation Army taking over. And it could eventually, though it is nowhere near doing so yet, provide an additional rationale for the Nato forces entering Kosovo ahead of an agreement with Milosevic.

None of this means that the British have secured agreement among the European Allies that war, even under favourable circumstances, should if necessary be made on the ground as well as in the air. In particular there is the question of the French, whose solidarity has so far been the greatest, but for whom the issue is least academic, since they would be committing real forces if the moment came. The signs in Paris are that they have not yet made up their minds. The belief in London is that they will in the end not shrink from such an operation, any more than they did in the Gulf.

The previous government would have expressed its contempt for its less certain European allies by now, almost certainly ensuring that agreement would be impossible when it was needed. But the intelligence of the current approach is to treat those allies sympathetically, recognising, for example, that a country with a fragile coalition needs to be more cautious than one with an overwhelming parliamentary majority; and understanding that there is no point in forcing a formal decision before it is necessary, while maximising the chances of agreement if and when it does become necessary. Cook's progress this week suggests that the strategy is working. In theory, at least, it may never be necessary. But in case it is, Tony Blair, filling the vacuum left by the slippage of authority in Washington, is coaxing the Allies forward to the alternative, if and when the generals agree that the Serbian forces are sufficiently enfeebled to make it practical.

This is a good deal more than papering over the cracks of a divided Alliance to impress Milosevic. The Government's relative reticence should not disguise the importance of the change of gear this week. And in such circumstances the perceived disadvantages of indicting Slobodan Milosevic suddenly seem to matter hardly at all.