In Slavonia , the first armed conflicts were clashes in Pakrac , and Borovo Selo near Vukovar . Western Slavonia was occupied in August 1991 , following an advance by the Yugoslav forces north from Banja Luka across the Sava River . This was partially pushed back by the Croatian Army in operations named Otkos 10 , and Orkan 91 , which established a front line around Okučani and south of Pakrac that would hold virtually unchanged for more than three years until Operation Flash in May 1995 . Armed conflict in the eastern Slavonia , culminating in the Battle of Vukovar and a subsequent massacre , also included heavy fighting and the successful defence of Osijek and Vinkovci . The front line stabilized and a ceasefire was agreed to on 2 January 1992 , coming into force the next day . After the ceasefire , United Nations Protection Force was deployed to the occupied areas , but intermittent artillery and rocket attacks , launched from Serb-held areas of Bosnia , continued in several areas of Slavonia , especially in Slavonski Brod and Županja . The war effectively ended in 1995 with Croatia achieving a decisive victory over the RSK in August 1995 . The remaining occupied areas — eastern Slavonia — were restored to Croatia pursuant to the Erdut Agreement of November 1995 , with the process concluded in mid-January 1998
massacre
Vukovar massacre
Slavonia