It's hard to hear the word Kosovo these days without being perplexed by two trusty aphorisms from the past:

From Yogi Berra: "It ain't over till it's over."

And from Shakespeare: "All's well that ends well."

The problem is that you can't really apply the second bit of wisdom until you're sure of the first one. It's awfully tough to jump into prudent evaluations of the peace agreements until we know for certain that the war is over.

A big part of the problem is that we're dealing not just with one head of state whose word nobody takes too seriously, but with two. If former President George Bush thought he had a crafty opponent in Saddam Hussein, he knows now that Iraq's leader was a piker at bobbing, ducking, and weaving compared to Serbia's President Slobodan Milosevic. But the real master at making it up as you go along is Bill Clinton himself, without whose ambiguities the United States might well never have gotten itself into the Kosovo conflict.

I know that's a stiff charge, so it's important also to acknowledge that Mr. Clinton in 1992 was handed two not-very-helpful inheritances from the Bush administration. The first was a terribly messy situation in southeast Europe. The second was the precedent of making a big deal over a war effort, and then leaving it half finished the way we did in the Gulf War in 1991. So I'm hardly holding up Republican foreign policy of the previous few years as a model of what the present administration ought to have done.

But hey, President Clinton's a bright man, and it should have been easy for him to learn from the mistakes that so closely preceded him. Instead, he has tended to repeat and even to amplify them. If a man is really as evil as both the war crimes tribunal and President Clinton say Mr. Milosevic is, shouldn't we have learned by now that it's fully as just to try to destroy that man as it is to ransack his people's country? If all this is really his fault, why get distracted? Go for the target.

But that, of course, suggests a second lesson Mr. Clinton didn't learn. As central and crucial a role as the U.S. president plays in leading world affairs, not even a president should try to do it alone. War is not a game like presidential politics, where you gather some of your old Arkansas cronies to calculate a strategy for the next 24 hours. The U.S. Constitution has some things to say about making war official, about the involvement of Congress in any war effort-and some of those issues have been consistently ignored by Democratic and Republican administrations alike ever since Vietnam. But such sidestepping of the Constitution has not been for our national good. In the process, we've gotten terribly sloppy even about stating the goals of particular wars. And if the goals are unclear, how can anyone know when the goals have been achieved-or if indeed any particular war is over?

In the Kosovo conflict, President Clinton regularly and cleverly used that unofficial status of the war to his own advantage. In the same way that "is" doesn't necessarily mean "is" in his personal life, so words in the last three months have consistently lost their meaning in the tracking of any official war policy. A firm, if ill-founded, pledge never to consider ground troops? A rock-hard commitment to protect the Kosovars against ethnic cleansing? A promise that we'd accept no compromises from the evil Milosevic? But as each promise ended up meaning something other than what it seemed to mean, what confidence could Americans possibly hold when their president said the war had been won?

If all those ambiguities weren't enough of a caution about premature celebration, the bizarre Russian involvement occupying the Pristina airport recently should have galvanized everybody's attention. Nor should anybody suppose this was just some unhandy, unilateral, unseemly push by a few uppity Russian troops. After all, the Russians had been sought out by the Clinton administration to help broker the "peace"-and if ever there were a sad symbol of our own weaknesses, such pitiful solicitation by an American government was that symbol. Clinton hack Strobe Talbott, the State Department honcho who never heard a Russian promise he didn't believe, has been left now to carry on the pretense that Moscow really wants to work for the common good.

A leader, the book of Proverbs says again and again, earns trust by showing himself trustworthy. But that seems a foreign idea to Bill Clinton, Slobodan Milosevic, Saddam Hussein, and a host of others who assume it is by force or craft or stealth or cunning that they earn the right to lead a people.