The Serbian attacks across the border into Albania reported last night show just how great the dangers are of the war in Yugoslavia spreading beyond Kosovo and Yugoslavia.
Macedonia and Montenegro risk being drawn into the conflict. What began as a surgical bombing offensive by Nato has become something very much bigger as hundreds more aircraft are committed to the attack, with major consequences not only for Yugoslavia itself, but also for the credibility of the alliance.
Even a tragic event such as the bombing of a civilian train in Yugoslavia only serves to show how remarkably effective the 18-day Nato campaign appears to have been in avoiding civilian casualties.
But, for all their precision and destructive power, the bombing has proved unable to halt the ethnic cleansing of Kosovo Albanians or the wholesale destruction of Albanian homes and villages in the province.
While Serbian tanks and artillery remain protected from attack in civilian areas, the real objective of this enormous exercise remains frustratingly elusive. Reports that Serbian forces are digging into areas from which they have driven the ethnic Albanians emphasise ever more strongly the inescapable reality that air bombardment alone cannot stop the war crimes.
Regardless of what the Nato allies say, it is impossible to see how the Kosovo question can be resolved without the use of ground troops to enforce the peace. Short of such a step, the alliance can give little indication of how it will resolve the conflict if, as looks likely on present showing, President Slobodan Milosevic continues his defiance.
Despite the damage being wrought from the air, Mr Milosevic still seems intent on seeing his forces achieve their objective. But the longer this goes on, the greater the danger of escalation into a wider Balkan war.
From the start, Nato leaders have stressed the need to prevent history from repeating itself in this troubled part of the world. But as events unfold, the possibility of a spreading conflict together with more suffering in Kosovo itself looks increasingly likely.