BELGRADE, Yugoslavia: Student protesters in Yugoslavia may have won a powerful ally: the army. A group of students emerged from a meeting with General Momcilo Perisic, head of the Yugoslav army, with guarantees that he would not interfere with their pro-democracy demonstrations. "We got firm assurances it will be so, and we are very pleased," said Dusan Vasiljevic, one of the students. If the army holds to its pledge, it represents a shift in the role that the military will play in Belgrade. In March of 1991, Serb President Slobodan Milosevic brought army tanks onto the streets of Belgrade to halt protests. He also used the military to launch wars in Croatia later that year and in Bosnia in 1992. But Milosevic has neglected the army in favor of a strong police force, a slight that may cost him. The students have also asked for a meeting with Serbia's police chief, Zoran Sokolovic, to demand the removal of his forces from Belgrade streets. Seven weeks of protests have accomplished relatively little. But if the students convince the police and military to stay out of the political dispute, they have already won a battle for democracy in Belgrade.