The sight of US troops flushing guerrillas out of mountain hiding places on the Kosovo-Macedonia border is the latest sign of NATO desperation to stop another Balkan war before it starts.
Memories are fresh of how the too-little-too-late remedies in Bosnia and Kosovo saw those wars mushroom out of control, and NATO leaders want to avoid the same mistake with the simmering ethnic conflict in Macedonia.
Hence extreme robustness - at least for now.
NATO has shown no hesitation in opening fire on ethnic Albanian rebels, nor in inviting Serbia - its enemy two years ago - to bring its troops back into a border buffer zone. And more troops, including, at France's suggestion, perhaps a force controlled by the European Union, may be on the way to bolster security in Macedonia.
That same robustness has seen Bosnia's senior Western diplomat, Mr Wolfgang Petritsch, this week sack the Croat presidency member, Mr Ante Jelavic, after he called for the Croats to set up their own breakaway state.
All of this is designed to squash nationalism before it starts and avoid the nightmare in which one Balkan crisis feeds into another. Independence for Bosnia's Croats, for instance, could encourage Bosnia's Serbs to go the same way. Which would only make the ethnic Albanians in Kosovo and Macedonia all the more determined to make their own land-grab.
"NATO is petrified that the whole thing may unravel, which is why they are trying to reassert some authority," said Dr Karin von Hippel, a former UN diplomat in Kosovo. "NATO knows if it doesn't get a handle on things, the situation could really explode."
All eyes are on Macedonia, the only part of former Yugoslavia to avoid the bloodshed which has engulfed the rest of the region in the past decade.
The powder-keg here is a familiar one: two ethnic groups locking horns, in this case a restive ethnic Albanian minority wanting more rights, and a Macedonian government worried about being "swamped".
"This is the doomsday scenario for NATO," said Tim Judah, author of Kosovo: War and Revenge. "Macedonia is the war it had hoped to scotch."
Already there are signs of the spreading war, though: on Wednesday Bulgaria gave Macedonia military equipment and may also send troops. Ethnic Albanians are getting help from Albanians across the border in Kosovo.
For many in NATO, tackling all of this head-on is seen as a better approach than the wait-and-see favoured in previous Balkan wars.
In Bosnia the Alliance waded in after four years of war, finally bombing the Serbs to the negotiating table.
In Kosovo three years later, the bombers again went out, but only after Serbia called bluff after bluff, leaving the alliance falling into a war because the alternative was to see its credibility shattered.
But robustness has its own risks, in this case, of a bloody nose.
Tackling the guerrillas head on invites the prospect of retaliation, and a new nightmare of being dragged into a bitter guerrilla war with a steady stream of body bags being sent home.
"I don't think America wants to withdraw from Kosovo like it did from Somalia. There is too much at stake for Europe," said von Hippel. "But if the guerrillas kill US soldiers, that will change everything."
The problem is that in this part of the Balkans, unlike Bosnia, there is much unfinished business. Bosnia has a workable peace plan. Kosovo and Macedonia have open wounds.
Kosovo's Albanian majority demands independence. Serbia refuses to even consider it. In Macedonia the growing proportion of ethnic Albanians demand more rights. The Macedonians see that as a looming threat. Undoubtedly the warriors here are led by cynics willing to exploit hatred for their own ends. The trouble is, there is so much hatred here to exploit.
On the positive side, many in the Balkans want to avoid war.
THE UPSURGE of violence is in part at least a sign of desperation among nationalists who are losing ground. Recent elections in both Bosnia and Kosovo have produced big wins for moderate parties. In Macedonia many Albanian and Macedonian politicians work together. A bit of NATO muscle might just be the glue to allow them to see off the extremists.
Large dollops of aid will be vital to the task, more than has so far been promised. So, too, will unity in an international community already badly split between inter-European rows, rows over the European army and the jostling between America and Russia over the future of ballistic missile defence.
But if the great mission to the Balkans fails, a new, sadder conclusion may have to be faced, that peace, in this troubled region, can come not with integration, but with ethnic division.
