Military operations in World War II on the territory of Yugoslavia started on 6 April 1941, when the kingdom was swiftly conquered by Axis forces and partitioned between Germany, Italy, Hungary, Bulgaria and client regimes. Subsequently, a guerrilla liberation war was fought against the Axis occupying forces and their locally established puppet regimes, including the Independent State of Croatia and the Government of National Salvation in Serbia, by the Communist-led republican Yugoslav Partisans. Simultaneously, a multi-side civil war was waged between the Partisans, the Serbian royalist Chetniks, Croatian nationalist Ustaše and Home Guard, as well as Slovene Home Guard troops.