The modern Albanian-Serbian conflict has its roots in the expulsion of the Albanians in 1877–1878 from areas that became incorporated into the Principality of Serbia. During and after the Serbian–Ottoman War of 1876–78, between 30,000 and 70,000 Muslims, mostly Albanians, were expelled by the Serb army from the Sanjak of Niš and fled to the Kosovo Vilayet. According to Austrian data, by the 1890s Kosovo was 70% Muslim (nearly entirely of Albanian descent) and less than 30% non-Muslim (primarily Serbs). At the turn of the century in 1901, widespread massacres were committed against the Serbian population by the Albanian population across the Kosovo Vilayet.