The Yugoslav Partisans fought both a guerrilla campaign against the Axis occupiers and a civil war against the Chetniks. The Independent State of Croatia was established as a Nazi puppet-state, ruled by the fascist militia known as the Ustaše. During this time the Independent State of Croatia created extermination camps for anti-fascists, communists, Serbs, Muslims, Gypsies and Jews, one of the most infamous being the Jasenovac concentration camp.