After the adoption of the Constitutional Decision of the Parliament on the Sovereignty and Independence of the Republic of Croatia, on June 25, 1991, open Greater Serbia aggression against the Republic of Croatia began, precisely with attacks by Serbian forces, with the support of the JNA, in the Banovina area. The next day, police stations in Glina, Hrvatska Kostajnica, Kozibrod, Kraljevcani and Dragotinci were attacked. Due to the insufficient number of members of the police for securing and defending the Banovina, employees from the Zagreb Police Department, the Bjelovar Police Department, the Kutina Police Department, the Slavonski Brod Police Department and the Varaždin Police Department come to the area. Despite the lack of weapons and military equipment, and logistics and preparedness for war operations, the Croatian police successfully resisted attacks by Serb forces and the JNA from late June to late July 1991, when after the Serbian offensive operation "Žaoka" Croatian forces fully they lose control of most of the Banovina area.