On the basis of the initial work done by historian Filip Škiljan, editor Milan Radanovic coordinated the preparation of expert and scientific papers written by Milan Koljanin, Igor Mrkalj and Aleksandra Kučeković about forced religious conversion of Serbs to Catholicism in Croatia, primarily from the founding of the so-called Croatian Orthodox Church. This collection of research papers aims to shed light on the sociopolitical circumstances in the Independent State of Croatia, as well as international activities which formed the backdrop of the process of converting Orthodox Serbs to Catholicism. To a significant extent religious conversion neither helped nor protected Serbs from Ustasha’s crimes and violence, but primarily served as means of pacifying the population and reducing numbers in the Partisan movement. This collection provides the first comprehensive overview of this aspect of WWII history, which is most frequently the subject of various controversies, rather than systematic scientific research.