Christendom

The conversion of Constantine ... was the effective beginning of “Christendom,” namely, of that particular form of the Christian religion that consists of a strong alliance of Christianity with political and social power, sometimes amounting to the practical identification of Christianity with the dominant forces of the society in which it finds itself.

— Christendom

When Christianity came into the world the task was simply to proclaim Christianity. The same is the case wherever Christianity is introduced into a country the religion of which is not Christianity.

— Christendom