Luka. The fortress existed as a military spot until 1851 when the army left and the walls were demolished by the local population who used the walls to build their own houses. A huge fire in 1882 destroyed 119 houses, 56 big commercial stores, schools, an Eastern Orthodox church, and 140 families lost roofs over their heads. The next year the Austrian authorities opened a large sawmill at the foot of the mountain Kozara, which is the first industrial object in the history of Prijedor. The years after the fire brought on intensive development of the town, encompassing both private and state-owned structures. The wood was replaced with modern building materials, the streets were designed at right angles and the first town plan was created. New buildings were built, such as the Serbian elementary school, the Catholic Church, the Eastern Orthodox Church, and a hotel. The first cultural associations appeared in the town as well as libraries, reading rooms and a printing house. The end of the First World War created a fledgling state—the Kingdom of Serbs, Croats, and Slovenes—with Bosnia-Herzegovina as a part of it. Prijedor was an important place as the trade and craft centre of the whole region. The opening of the iron ore mine in Ljubija near Prijedor in 1916, which employed about 4,000 workers, strengthened the economy of the town. During that period, the mine was one of the biggest and most modern iron ore mines in Europe. From 1929 to 1941, Prijedor was part of the Vrbas Banovina of the Kingdom of Yugoslavia. World War II The memorial centre Mrakovica at Kozara, the work of the academic artist Dušan Džamonja, is dedicated to this region's Yugoslav partisans resistance victims during WWII. Some villages around Prijedor and Kozara Mountain suffered the deaths of tremendous numbers of civilians, who were killed by the Ustaše and taken to different concentration camps during genocide campaign; the most notorious of these was the Jastrebarsko Concentration Camp, where Serb children were imprisoned. Bosnian war During the Bosnian war (1992–1995), the area near Prijedor housed the infamous Omarska camp, Keraterm camp, and Trnopolje camp established in 1992 for the Bosniak and Croat population. Demographics Population Ethnic composition Education The first forms of organized education can be tracked back in the first half of the 19th century. In 1834 Prijedor had the "Serbian elementary school" that later with so-called "Communal school" was