If Slobodan Milosevic is truly ready to end his oppression of Kosovo, Washington will soon witness a good deal of scurrying and second-guessing, especially among those who opposed NATO's war. Some will deny having espoused the positions they espoused, others will explain why they were right even if things did not turn out quite as badly as they predicted.

There will be the usual political gamesmanship in all this. Republican leaders who objected even to a limited war, never mind an invasion of Belgrade, now feel free to complain that Milosevic remains in office.

But the debate will be far more than a game. The lessons Americans draw from the war in Kosovo will help determine how NATO shapes the peace and how it rises to meet future threats. And in many cases, the instincts that led critics to question NATO's role will reassert themselves.

Some of those who opposed U.S. involvement in the war now will oppose, just as wrongly, a long-term commitment of U.S. troops. Some who urged an end to bombing as soon as Serb civilians began to die will now, with the same misguided good intentions, want to start rebuilding Serbia, even before Milosevic loses power.

Two central questions will underlie these debates. Does the United States have a compelling national interest in Kosovo's fate? And if so, has President Clinton defended that interest in an optimal way?

The second question is the more difficult. Even if the peace agreement now proceeds smoothly -- if all the Kosovars who wish to do so now return home -- no one could claim a happy outcome. Too many Kosovars have been killed and raped, too many families torn apart, too many towns and villages destroyed, and too many innocent Serb bystanders have also been killed for anyone to claim victory.

There is room to criticize the administration -- for neglecting Kosovo from 1993 until 1998, for issuing too many empty threats once it took notice, for ruling out ground troops before bombing began.

But anyone who makes such criticisms, as I have, also must acknowledge that there were no easy or obvious alternatives along the way. The United States could have focused on Kosovo during the Dayton peace talks, but would it then have been worth risking the Bosnia peace deal? NATO could have assembled a ground force before launching its air war, but Milosevic still would have had time to implement his strategy of terror against the Kosovars.

Better, then, for all sides to show some humility. Clinton did not adequately prepare for Milosevic's sudden acceleration of brutality. But many of Clinton's critics instructed us that the Serb mentality of victimhood would keep Milosevic from ever surrendering, that military history proved air power could never do the job, that the campaign was a debacle because it did not succeed within a week or two.

Clinton warned from the start that the campaign might take time. He and his 18 NATO colleagues preserved their unity against great odds. They set a policy and they stuck to it.

That neither they nor their critics could forecast how things would turn out -- the inherent unpredictability of armed conflict -- is one more reason to avoid war whenever possible. But that is not the same as avoiding war at any cost. In this case, the cost of permitting Milosevic to brutalize Kosovo with impunity would have been too high.

From the start, many critics of "Clinton's war" argued that the United States had no interest in the distant, troubled Balkans. Just last Thursday, Republican candidate Steve Forbes spoke out against sending U.S. troops even as part of a peacekeeping force. "Nothing could be more misguided," he said.

In fact, walking away would be far more misguided. America's peace and prosperity depend on stability and democracy in Europe. For a half century, Republicans and Democrats alike understood that basic premise, understood the importance of standing up to the Soviet threat in defense of democracy.

Now that half-century struggle is paying off. More than could have been imagined even a decade ago, democracy is triumphant. Erstwhile Warsaw Pact captives Poland, Hungary and the Czech Republic are free nations allied with the United States in its fight against Milosevic. Last week, Slovakia took another important step toward joining this world with its presidential election. Only three old-style strongmen -- in Croatia, Belarus and of course Serbia -- now buck the trend.

German Foreign Minister Joschka Fischer, visiting Washington two weeks ago, explained why a holdout like Milosevic threatens European (and by extension, American) security. It's not that he can conquer the continent and break through to the English Channel as Hitler did. But Milosevic would fit into Hitler's Europe, Fischer said, with his radical nationalism and his "fighting for living space in an aggressive way against neighbors."

"His policy is a declaration of war against the policy of European integration," Fischer said. "It's not only a question of morality, of human rights. It's a question of security and stability in Europe."

If Milosevic prevails, his brand of brutal nationalism will spread. If the Kosovo war marks the beginning of his demise, then other countries in transition will more likely see their future in democracy, fair treatment of minorities and peaceful neighborly relations.

The United States for decades stationed hundreds of thousands of troops in Germany to defend those principles. Surely it's worth keeping 6,000 in Bosnia and another 7,000 in Kosovo to finish the job.

The writer is a member of the editorial page staff.