Which religion was Orthodox at the beginning of the 20th century?

Orthodoxy is part of the Christian religion. The division into a Catholic and an Orthodox part appeared in the fifth century as a result of the Council of Nicaea in terms of completely insignificant and completely trifling details for a modern inhabitant in the rite of service. And then over time, the division only grew. Orthodoxy still exists in some countries. Moreover, it is called so only in our country. In Western history, it is called “orthodoxy.”