The lessons President Clinton has drawn from the Kosovo war pose a noble and ambitious challenge not only for the American people but also for Clinton and for his unchosen successor. National will and inspired leadership must come together if the promises Clinton has fashioned out of the Kosovo experience are to be fulfilled.

The president promises a future in which Americans stand ready to intervene militarily if they can stop wholesale racial or ethnic slaughter "within or beyond" other nations' borders. He sees a future in which the United States actively works with the United Nations and other international bodies to thwart and punish political mass murderers.

He promises a new world order -- although he shuns that specific phrase, briefly popularized and then quickly abandoned by President Bush during the Gulf War.

Traveling through the Balkans on June 22 Clinton committed the United States not to walk away from the consequences of waging low-risk high-tech warfare on a devastated Third World nation, as he and Bush did in Iraq and elsewhere.

"We must win the peace," Clinton told NATO troops in Macedonia. "If we can do this here . . . we can then say to the people of the world, `Whether you live in Africa or Central Europe or any other place, if somebody comes after innocent civilians and tries to kill them en masse because of their race, their ethnic background or their religion and it is within our power to stop it, we will stop it.' "

A Clinton Doctrine of humanitarian warfare is taking shape. Its elaboration by Clinton at Aviano air base, to Kosovo refugees in Macedonia and in a CNN interview on the same European trip cannot be dismissed as mere rhetoric. Words like these will have effect whatever Clinton's own ultimate use and view of them.

Clinton has been serious on Kosovo. He did not treat the air campaign as a casual matter, as he repeatedly did with missile strikes in Iraq. His performance in Kosovo does not automatically erase his reputation for employing words as if they have no tomorrow. But it should earn sober consideration of his view of the consequences of a war he led.

This time the president has acted boldly as well as spoken ambitiously. He dispatched 56 FBI forensic experts to Kosovo last week to gather evidence for The Hague-based U.N. tribunal considering war crimes in ex-Yugoslavia. And the United States announced a $5 million bounty for the delivery of Slobodan Milosevic to the tribunal.

This active U.S. support for the tribunal's redoubtable chief prosecutor, Louise Arbour, contrasts significantly with President Bush's quick turning away from consideration of pursuing Saddam as a war criminal in 1991. It contrasts even with Clinton's own record on international justice. A year ago his administration helped block the establishment of a U.N. International Criminal Court with strong prosecutorial teeth.

Clinton's intention to keep the United States intimately involved in European-led and -financed peacekeeping and reconstruction in the Balkans merits support by Congress and the public. He understands that NATO's 11-week bombing campaign, carried out largely by U.S. planes, can have no long-lasting positive impact -- or ultimate justification -- without seeing through postwar efforts to achieve justice and democracy in the Balkans.

The viability of a strategic doctrine built on the duty to intervene will now be tested on the ground. Europe's economic power and the threat posed by the Balkans to the continent's stability give NATO both the ability and the clear need to help redeem Clinton's promises to the people of the region. Success is possible, although far from guaranteed.

Less clear is how the president intends to engage America in reforming an international system that has routinely allowed the horrors of Iraq, Rwanda, Bosnia, Kosovo and elsewhere to fester, explode and then fester toward new explosion.

That these horrors occurred inside national frontiers provided major powers with a handy excuse not to get involved in the past. The Kosovo campaign, as interpreted by Clinton, has dismantled borders as a barrier to military action. Leaders must now decide at what point intervening to stop and punish mass murder becomes their responsibility -- wherever it occurs.

NATO bombing on its southern fringe but still inside Europe without a specific U.N. mandate -- i.e., the Kosovo campaign -- met the test in my view. But for NATO to take on that duty on its own in Africa or the Middle East, as Clinton seems to suggest could now happen, would be dangerous overreaching for the alliance and the United States.

Clinton has presented the nation with a block of marble that has to be carved into a statue by words and actions from him and from those who would succeed him.

Reasonable political leaders can disagree on where America's duty to intervene abroad begins and ends, and reasonable voters can then choose among them. This is a question neither candidates nor voters can turn away from in the U.S. election campaigns now rushing over the horizon toward us.