There is a bar-owner in Kosovo's capital, Pristina, who prefers not to be named and who delighted, last autumn, in showing foreign journalists what he would do should NATO bomb his country.
Behind his bar he has a machinegun and a grenade, and he motions to the street outside, full of mostly Albanian shops. "I will got out and shoot them," he says.
And not just him. The biggest worry now confronting the West's military planners as they prepare for possible air strikes against Serbia is the potential killing spree of the bar-owner and others like him.
"Our biggest fear is that air strikes would be used as an excuse by Serbian paramilitary units to enter Kosovo and attack ethnic Albanian civilians," said one diplomat.
The worry is that Kosovo's Serbs, unable to halt NATO air power or take on the Kosovo Liberation Army guerrillas in the countryside, will seek retribution where they can, among Albanian civilians living in Kosovo's towns.
"The guerrillas have no effective military presence inside the cities and large towns where most ethnic Albanians live," said a Western military monitor in Pristina. "People there would be sitting ducks for paramilitary squads intent on making somebody pay for NATO's actions."
Already the streets of Pristina echo each night to the volleys of machinegun bullets fired from the cars of armed Serb civilians. Most have taken up a police offer to get free guns in recent months. For now, this shooting is only in the air.
Kosovo's Serbs are traumatised. Though most of the victims of this war are Albanian, the guerrillas have kidnapped and killed Serbs, and most live with the fear of being overwhelmed by their foes, who outnumber them more than 10 to one. Official propaganda stokes up the fear of the "terrorists" waiting to come down from the hills and kill them.
"NATO could respond effectively with air power if Belgrade started moving or firing artillery or tanks or armoured vehicles in Kosovo. The kind of thugs we saw operating in Bosnia and Croatia would pose a different kind of threat," said the diplomat, who would not be named.
Even stopping the tanks would pose problems. A full-on armoured thrust could lead to a massacre, or drive an army of Albanian civilians to Kosovo's borders with Albania and Macedonia, triggering a fresh humanitarian crisis.
Yet this is what Serbia says will happen if NATO bombs start to fall. "There is no problem for us to deal with the rest of the terrorists in Kosovo and we shall do so immediately if our country is attacked," said the commander of Yugoslavia's Third Army, Col Gen Nebojsa Pavkovic, deployed in Kosovo.
Hitting moving tanks in bad weather is more difficult for pilots than bombing fixed targets like radar sites and command bunkers, and more risky.
NATO says Yugoslavia has upgraded its air defence systems with modern Russian equipment. "Taking this on with air power will not be easy," said US Air Force Commander Gen Michael Ryan. "There is a distinct possibility that we will lose aircraft."
The key problem for NATO is that Kosovo has no proper front lines. The Albanians and Serbs live among each other. Bombing one side without hitting the other is difficult.
Another worry is that Serb willpower to withstand the air strikes may prove stronger than the West's determination to press on despite losses.
In effect, air strikes would be a game of brinkmanship played out hour by hour in the skies. Only truly massive bombing would break Yugoslavia's ability to fight the Albanian guerrillas, who are at present being contained by only a fraction of the Serb forces deployed in the province.
The air strikes now planned are designed to "punish" the Serbs, and they assume that Yugoslav President Slobodan Milosevic will throw in the towel rather than see his expensive military equipment destroyed.
But if he refuses, and NATO losses mount, the Western alliance will find its resolve tested. Many US senators are already asking this week why the lives of their troops should be risked in a province which, in a recent opinion poll, only 45 per cent of Americans could place on a world map.