The Ustaše persecuted the Serbs, who were Orthodox Christians. They were tolerant toward the Bosnian Muslims, claiming that the Muslims were actually ethnic Croats that converted to Islam during the Ottoman Turk occupation of Bosnia. The state even converted a former museum in Zagreb for use as a mosque. The basic principles of the movement were laid out by Pavelić in his 1929 pamphlet "Principles of the Ustaše Movement."