Part 1 - Did Jesus and His Disciples Teach the Trinity Doctrine? - Anathemas Pronounced on Opposers

In 325 C.E., a council of bishops in Nicea in Asia Minor formulated a creed that declared the Son of God to be  "true God" just as the Father was "true God." Part of that creed stated: 

"But as for those who say, There  [a time] when [the Son] was not, and, Before being born He was not, and that He came into existence out of nothing, or who assert that the Son of God is of a different hypostasis or  substance, or is created, or is subject to alteration or change-these the Catholic Church anathematizes. 

Thus, anyone who believed that the Son of God was not co-eternal with the Father or that the Son was created was consigned to be everlasting damnation. One can imagine the pressure to conform that this put on the mass of ordinary believers.

In the year 381 C.E., another council met at Constantinople and declared that the holy spirit should worshiped and glorified just as the Father and Son were. One year later, in 382 C.E., another synod met in Constantinople and affirmed the full divinity of the holy spirit. That same year, before a council in Rome, Pope Damascus, included the following statements: "

Next time: Part 1 - Did Jesus and His Disciples Teach the Trinity Doctrine? - Conclusion of  Anathemas Pronounced  on Opposers

From the jw.org publications