The Battle of Borovo Selo on 2 May 1991 (known in Croatia as the Borovo Selo massacre, Croatian: Pokolj u Borovom Selu and in Serbia as the Borovo Selo incident, Serbian: Инцидент у Боровом Селу) was one of the first armed clashes in the conflict which became known as the Croatian War of Independence. The clash was precipitated by months of rising ethnic tensions and armed combat in Pakrac and at the Plitvice Lakes in March. The immediate cause for the confrontation in the village of Borovo Selo, just north of Vukovar, was a failed attempt to replace a Yugoslav flag in the village with a Croatian one. The unauthorised effort by four Croatian policemen resulted in the capture of two by a Croatian Serb militia in the village. To retrieve the captives, Croatian authorities deployed additional police, who drove into an ambush.