In Kosovo, the North Atlantic Treaty Organization may have stumbled into a conflict that could define the security structure of Europe for a generation, with unpredictable consequences for the United States' role as a world power.
That's because the reasoning behind US and NATO involvement in this troubled corner of the Balkans marks a large change in behavior for the Western alliance.
NATO was born as a defensive shield against Soviet expansionism, but in Kosovo it is dropping bombs to stop a sovereign state from abusing a group of its own citizens.
Having crossed this threshold, will the US and its allies now move more aggressively to enforce standards of behavior in troubled areas of Europe, or, indeed, the world?
Meanwhile, the bombing campaign is highlighting a number of separate geopolitical trends. These range from Germany's reemergence as an active military force to the ever-increasing Western reliance on air power as a form of antiseptic persuasion.
"This is a struggle about the kind of world we're going to live in in the future," said Gen. Wesley Clark, supreme allied commander, Europe, in a March 28 broadcast interview. "Are we going to have old-style Communist dictators that rule by propaganda and fear and terror ... or are we all going to move together into a 21st century that has the right values and the right standards for all people?"
It is the end of the cold war that has made the issue of humanitarian intervention acute for the US and its NATO allies.
During the standoff with the Soviet Union, the leaders of the West had larger geopolitical fish to fry. Virtually every diplomatic action was weighed in terms of its importance to that long struggle.
But the collapse of the Soviet regime has allowed - some would say forced - the West to pay attention to others' need for help. At the same time, it has left the North Atlantic alliance looking for new reasons to justify its existence.
In interventions in Somalia and Haiti, the United States has already grappled with some of the difficulties of trying to play the role of heavily armed good guy.
But the Yugoslav bombing campaign is of a much larger scale. It involves the whole NATO alliance, largely united. And it is taking place without official United Nations approval.
Centuries of traditional international law have drawn a distinction between the importance of a nation's external aggression versus its internal affairs. Yet in the Kosovo campaign, NATO is trying to coerce strongman Slobodan Milosevic to end atrocities against a Kosovar Albanian minority that the West has said should remain a part of the Yugoslav nation.
In essence, the campaign could mark the rise of a new interventionist internationalism, such as that seen in the Anti-Genocide Convention of 1948, which calls on signatories to prevent ethnic cleansing.
"If this is successful, it will strengthen the principle of humanitarian intervention," says Paul Magnarella, a law professor at the University of Florida, Gainesville.
As of this writing, the operation's success appears open to question. Meanwhile, experts debate whether this campaign, the most extensive operation ever of the most powerful alliance in history, will set precedents for years to come. What would NATO do now if Russia tries again to crush its separatist Chechens?
By moving to aid Kosovar Albanians, the US and its allies may increase the pressure on themselves to aid other hard-pressed groups in the future. The West didn't act when Rwanda exploded in flames in 1994, with hundreds of thousands of deaths. If that happened today, or again, what would a US president do?
Other nations may now also cite the Kosovo operation to justify their own moves. China and Pakistan, say, could intervene in India's troubled region of Kashmir. "They can point to this NATO intervention as a solid precedent," says Ted Galen Carpenter, a defense and foreign policy analyst at the Cato Institute.
Thus the implications of the current campaign go beyond the future of Kosovo itself. In addition, the move may mark the rise of something the US says it has long wanted: a more assertive Europe.
Throughout the long Balkans crisis, Europeans have been frustrated that such violence was occurring in their midst, yet their governments did not have the will or the means to do much about it.
BUT the current operations show that NATO is capable of acting in unison to ensure a stable Europe - although some members are less enthusiastic about the bombing operations than others.
Germany's role in particular is important. For decades, German leaders have understandably declined any show of military strength outside their own borders. Now their planes are flying in support of NATO's operations, meaning the German leadership may finally deem it time for them to assume a role commensurate with their economic and military size.
Finally, some experts say the West's reliance on bombing alone is indicative. It is hands-off coercion, and thus perhaps ineffective. "There are no great powers anymore because countries aren't willing to use their armies any more," says John Fine, a professor of Central and East European history at the University of Michigan.