Between 15,000 and 30,000 Bosnian government troops are encamped north of Sarajevo,awaiting orders to break through Bosnian Serb linessurrounding the embattled capital. Government officials have not said when or if they will attempt an attack to lift the three year old blockade. "If they do attack, it's going to be extremely bloody," reports Massimo Calabresi, TIME Central Europe correspondent. "The Bosnian Serbs have some 400 to 600 heavy weapons, and they will probably retaliate the same way they always do, by shelling civilians in Sarajevo."U.N. peacekeepers in the area would be caught between the two armies. Bosnian President Alija Izetbegovic said today hemight ask them to leaveif they interfere with his troops.