St. Nicholas was converted into the White Mosque, but the large number of Catholics, Ragusan and Saxon, caused the transformation of the town to Islam to be slower than in most of the other towns in the area. The area of Osat was liberated for a short time during the First Serbian Uprising (1804–13), under the leadership of Kara-Marko Vasić from Crvica. Upon the breakout of the uprising, Metropolitan Hadži Melentije Stevanović contacted Vasić, who met with the rebel leadership. After participating in battles on the Drina (1804), Vasić asked Karađorđe for an army to liberate Osat; Lazar Mutap was dispatched and the region came under rebel rule. In 1808, the Ottomans cleared out Osat, and by 1813, the rebels left the region. Austro-Hungarian period The town came under Austro-Hungarian rule in 1878, when the Congress of Berlin approved the occupation of the Bosnia Vilayet, which later in 1908 became a condominium under the joint control of Austria and Hungary. The natural mineral water springs Crni Guber ("Black Guber") developed into an important part of the local economy. The Bohemian company Mattoni established a distribution infrastructure to tap and export the water named Guber-Quelle ("Guber Spring") throughout the monarchy and abroad. The construction of a spa was recommended. Modern infrastructure such as administration, electricity, roads, schools, telephone, healthcare, a postal service and other things were introduced. Although the Austrian rulers tried to stop the spread of nationalism and favoured a multi-religious and multi-cultural makeup with religious tolerance under their hegemony, Serbian nationalism was viewed with suspicion and hostility, since it demanded a unification of Bosnia with Serbia. As modern education raised the levels of general literacy, ideas spread through the advent of newspapers and publications. The region became increasingly restless as nationalism spread to all groups. During the First World War, one of the region's main battle areas was in Eastern Bosnia and the Drina, from where the units of Austria-Hungary advanced towards the Kingdom of Serbia. In late summer 1914 Srebrenica was taken over by Serbian volunteers under Kosta Todorović but later retaken by Austro-Hungarian units. Following World War I, Bosnia was incorporated into the South Slav kingdom of Serbs, Croats and Slovenes, which later was renamed Yugoslavia. Second World War During the Second World War there were many atrocities committed by the Chetniks and Ustashas. Partisans fought Chetniks and Ustashe during the war and the people of Srebrenica