ALL EUROPE has a stake in the war in Kosovo, to see that it does not create a wider war, does not compound atrocities, does not become a clash of Serbia against Albania or of Christendom against Islam.
The trouble is that warring between Serbia's strong man, Slobodan Milosevic, and the Kosovo Liberation Army (KLA) of ethnic Albanian rebels threatens to provoke those things.
NATO's ultimatum to the two sides Thursday was a triumph for U.S. diplomacy. The alliance is committed to imposing a political settlement, giving neither side all it seeks through terror.
The ultimatum requires a cease-fire and a conference in France on Saturday. It holds Mr. Milosevic to promises he made last October.
The goal is to restore to predominantly Albanian Kosovo the autonomy it enjoyed even under former Yugoslav Communist rule, which Mr. Milosevic abolished in a fit of Serbian nationalist grandstanding 10 years ago. The ultimatum requires that the branch of the Yugoslav army known as the Serbian special police leave Kosovo but postpones questions of sovereignty for three years.
Why is this anyone's business outside Serbia? Because the Serbian policy of dislocating large populations threatens to engulf neighboring countries, notably Albania, Macedonia and Bosnia, with masses of refugees.
Because fanning Albanian nationalism could destabilize Albania itself, which has not recovered from its own anarchy, and Macedonia, where a third of the people are ethnic Albanians. And because it could lead to a wider war pitting Islamic countries against Orthodox Christian countries.
The ultimatums issued by NATO must be taken seriously by both Mr. Milosevic's Serbian regime and by the KLA extremists, or they won't work.
Agreement on manning a potential ground force may elude NATO and divide the European allies from the United States, which furnishes most of the air power. Mr. Milosevic, now formally Yugoslavia's president, counts on it.
The more united NATO in political will, the less likely its force will be challenged.