The Croatian fascist Ustashe created the Independent State of Croatia (NDH) four days after the German invasion of Yugoslavia. Croatia was set up as an Italian protectorate. Around a third of the population was Eastern Orthodox (ethnic Serbs). The Ustashe followed Nazi ideology, and set up a goal of creating an ethnically pure Greater Croatia; Jews, Gypsies and especially Serbs were targeted and victims of genocidal policies. The Ustashe recognized both Roman Catholicism and Islam as the national religions of Croatia, but held the position that Eastern Orthodoxy, as a symbol of Serb identity, was a dangerous foe. In the spring and summer of 1941 the genocide against Eastern Orthodox Serbs began and concentration camps like Jasenovac were created. Serbs were murdered and forcibly converted, in order to Croatize, and permanently destroy the Serbian Orthodox Church. The Catholic leadership in Croatia mostly supported the Ustashe actions. Eastern Orthodox bishops and priests were persecuted, arrested and tortured or killed (several hundreds) and hundreds (most) of Eastern Orthodox churches were closed, destroyed, or plundered by the Ustashe. Sometimes entire villages were locked inside the local Eastern Orthodox church and then set alight. Hundreds of thousands of Eastern Orthodox Serbs were forced to flee from Ustashe-held territories into territory of German-occupied Serbia. It was not until the end of the war that the Serbian Orthodox Church would function again in western parts of Yugoslavia.