With the Plitvice Lakes incident of late March/early April 1991, the Croatian War of Independence broke out between the Croatian government and the rebel ethnic Serbs of the SAO Krajina (heavily backed by the by-now Serb-controlled Yugoslav People's Army). On 1 April 1991, the SAO Krajina declared that it would secede from Croatia. Immediately after Croatia's declaration of independence, Croatian Serbs also formed the SAO Western Slavonia and the SAO of Eastern Slavonia, Baranja and Western Srijem. These three regions would combine into the self-proclaimed proto-state Republic of Serbian Krajina (RSK) on 19 December 1991.