Checkpoints sprouted like spring flowers across former Yugoslavia yesterday with tensions built up over many months bubbling over.
Kosovo's key junctions and roads are pegged out, alternatively, by Serb police backed by blue armoured cars and bedraggled-looking Albanian guerrillas in green camouflage smocks, both keen to stake out their web of front lines in advance of next week's peace talks.
In Yugoslavia proper, checkpoints are operating on the boundary line between the country's two constituent republics, Serbia and its little brother, Montenegro. The latter has announced that from next weekend foreigners will no longer need visas to visit it, and Serbia is anxious to make sure such people do not enter, visa-less, into its territory.
Montenegro's police are also out in force, worried that Serbia may be preparing military action to overthrow its West-leaning president, Mr Milo Dukanovic.
Mr Dukanovic has shown his pro-Western credentials by refusing to let Yugoslav air defence units fire on NATO jets, should these be ordered to bomb Serbia.
Montenegro is probably on a collision course with Serbia after last week refusing a demand that Serb customs officers take over from Montenegrins at the key port of Bar. Serb replacement officers who arrived at the port, where revenues are being withheld from central government, were turned away by police loyal to Mr Dukanovic.
Meanwhile, over the border in Bosnia, British and US troops have thrown up their own network of checkpoints in Serb territory, anxious to stop arms and mobs of protesters moving from nationalist strongholds in the east to the capital, Banja Luka, in the west.
All of this, plus a sudden dumping of snow, has reduced travel in the region to a crawl in which a passport is scarcely put away before a new checkpoint demands it be shown. In Kosovo this is further complicated because foreigners must show a "white paper" obtained from the Information Ministry.
The rebel Kosovo Liberation Army meanwhile issues its own white paper, and journalists are careful not to show the wrong white paper to the wrong checkpoints.
With the West threatening to bomb them in Kosovo and give away their key town of Brcko in Bosnia, the Serbs are in hostile mood. Making a routine crossing from Yugoslavia into Bosnia yesterday this reporter was relieved of 3,000 deutschmarks by the border guards. They had a perfectly valid reason for this - officially all such money should have been declared on entry. Yet, for this reporter, it was the first time in a year of crossings that the demand was suddenly made.
Two Serbian policemen were shot dead and a third was wounded overnight in Kosovo's capital, Pristina, in an apparent gangland attack, Serbian sources said yesterday.