 Prior to the outbreak of World War II, use of terror tactics had a long tradition in the area as various oppressed groups sought their freedom and atrocities were committed by all parties engaged in conflict in Yugoslavia.During the early stages of the occupation, the Ustaše had also recruited a number of Muslims to aid in the persecutions of the Serbs, and even though only a relatively small number of Croats and Muslims engaged in these activities, and many opposed them, those actions initiated a cycle of violence and retribution between the Catholics, Orthodox and Muslims, as each sought to rid the others from the territories they controlled.In particular, Ustaše ideologues were concerned with the large Serb minority in the NDH, and initiated acts of terror on a wide scale in May 1941.