President Clinton demonstrated determination and clarity in leading NATO's successful effort to drive the Serb army from Kosovo. But those leadership qualities have given way to crossed priorities and dangerously ambiguous deal-making with Russia in the war's messy aftermath.

Such change comes as no surprise. War focuses the mind and spirit and forces leaders to rise above their usual behavior, as Clinton did, or to sink below it into barbarity and cowardice, as Slobodan Milosevic did. Sudden peace distends the faculties, letting old habits rapidly take charge again.

Clinton has moved from the role of conqueror to the more familiar stance of conciliator here at the Group of Eight annual leadership summit. He has visibly sought to soothe a Russian military and political establishment that surprised and briefly humiliated NATO by seizing control of Pristina airport 10 days ago and then daring NATO to do anything about it.

The president hailed the U.S.-Russian agreement reached in Helsinki Friday night to share control of the airport and to include 3,600 Russian troops in the NATO-led Kosovo Force (KFOR) -- even though the agreement leaves the hardest parts of NATO-Russian cooperation cloaked in confusion and still to be resolved.

And Clinton has devoted his considerable talents in political marketing to turning this two-day gathering into an exercise in selling to Western audiences the leadership abilities of the new Russian prime minister, Sergei V. Stepashin, and his infirm and erratic boss, President Boris Yeltsin.

In his initial contacts with the leaders of the world's seven most affluent industrial democracies Friday night, Stepashin dropped Russia's angry rhetoric about NATO's bombing of Serbia. He promised Clinton, Britain's Tony Blair and the others that there would be "no more surprises" from the Russians like the dash to the airport, according to G-7 sources.

Stepashin's pledge reinforced the impression of some senior conference delegates that he and Yeltsin were caught by surprise themselves by the Russian army's move into Kosovo, and supported it only after the fact. That impression in turn made it easier for the G-7 leaders to welcome the ex-interior minister here as Yeltsin's apparent chosen successor, despite his lack of experience in foreign and economic affairs.

Husbanding his failing strength, Yeltsin will arrive in Cologne on Sunday to meet with Clinton and bless the Kosovo troop deployment deal as ending two months of strained relations between Moscow and Washington.

But the unresolved problems of fitting the Russians into a NATO force as protectors of the Serb minority and shrines in Kosovo promise new tensions and flashpoints in the weeks ahead. This Russian role, spelled out by Clinton in remarks to reporters here Friday night, risks making the Russians surrogates for the Serbs and targets for vengeful ethnic Albanians.

Russian units protecting shrines will be stationed inside protective envelopes of larger U.S., French and German forces, who will police the autonomous Kosovo province that will legally remain part of Serbia. The Russian enclaves in Kosovo bring to mind Churchill's description of the old mysterious Soviet Union: The Russian troops in Kosovo will be a land mine wrapped inside a time bomb in the middle of a hurricane.

And despite U.S. assertions that the Helsinki agreement guarantees a single, unified NATO command, the Russians say they will choose to obey or disobey orders on their own. No one in Helsinki or Cologne could explain this apparent contradiction. Everything is to be worked out on the ground.

Ambiguity is the enemy of the allied peace-enforcement operation needed in desolate, volatile Kosovo now. The success of the U.S.-led force in neighboring Bosnia has been built on intimidation and the coercion of potential trouble-makers into acceptance. Only clear, unchallenged direction by a single military command can keep the peace-keepers from coming under attack themselves.

The arrangements made with the Russians in Helsinki and Clinton's strangely diffident disowning of any intention to pursue Serb war criminals encourage uncertainty and ambiguity about the U.S. role. They also give the Russians plenty of room to return to a spoiling role if they do not like the way things play out in Kosovo.

Clinton is betting that his relationship with Yeltsin and the weakness of the Russian forces on the ground in Kosovo will ensure their acquiescence to NATO control. It could work out that way. But it will be a losing gamble if Clinton leaves the impression of investing more importance in diplomacy with Russia than he does in meeting the immediate military problems of Kosovo and the pursuit of justice for the war crimes that Milosevic's forces committed there.