Yugoslavia was invaded and split by the Axis forces in 1941 and Lika became a part of the Independent State of Croatia (NDH), an Axis puppet state led by the Ustaše that systematically slaughtered Serbs during World War II. On 27 July the Srb uprising started against the Ustaše in Lika, led by Yugoslav Partisans and Chetniks, accompanied with mass crimes against Croats in the region. In June 1943 the founding session of the State Anti-fascist Council for the National Liberation of Croatia (ZAVNOH) was held in Otočac in Lika, in the territory held by the Partisans. The war ended in 1945 and Croatia became a Socialist federal unit of the Socialist Federal Republic of Yugoslavia.