During the Bosnian War, there was an ethnic cleansing campaign committed by the Bosnian Serb political and military leadership – Army of the Republika Srpska, mostly against Bosniak and Croat civilians in the Prijedor region of Bosnia and Herzegovina in 1992 and 1993. The composition of non-Serbs was drastically reduced: out of a population of 50,000 Bosniaks and 6,000 Croats, only some 6,000 Bosniaks and 3,000 Croats remained in the municipality by the end of the war. After the Srebrenica massacre, Prijedor is the area with the second highest rate of civilian killings committed during the Bosnian War. According to the Sarajevo-based Research and Documentation Center (IDC), 4,868 people were killed or went missing in the Prijedor municipality during the war. Among them were 3,515 Bosniak civilians, 186 Croat civilians and 78 Serb civilians. As of October 2013, 96 mass graves have been located and around 2,100 victims have been identified, largely by DNA analysis.

The Bosnian War was an international armed conflict that took place in Bosnia and Herzegovina between 1992 and 1995. The war is commonly seen as having started on 6 April 1992, following a number of earlier violent incidents. The war ended on 14 December 1995 when the Dayton accords were signed. The main belligerents were the forces of the Republic of Bosnia and Herzegovina, the Republic of Herzeg-Bosnia, and the Republika Srpska, the latter two entities being proto-states led and supplied by Croatia and Serbia, respectively.