https://imperiumromanum.pl/en/roman-religion/christianization-of-ancient-rome/
The process of christianization of the Roman Empire was of great importance for the fate of the state. To a large extent, Christianity destabilized Rome.
ancient romeimperium romanumchristianization
https://dbpedia.org/page/Christianization_of_Bulgaria
Process by which 9th-century medieval Bulgaria converted to Christianity
christianization of bulgaria