The early church councils took place during the Church of Pergamus period described in Revelation 2.
The third of the seven churches was assaulted by two false doctrines: the doctrine of Balaam and the doctrine of the Nicolaitanes.
It is no coincidence that the doctrines of Sunday sacredness  and the Trinity  emerged at this time. Neither can find any authoritative support within the pages of the Bible. Both are claimed by the Roman Church as evidence of her ecclesiastical authority.
“Q. Have you any other proofs that they [Protestants] are not guided by the Scriptures?”
“A. Yes; so many that we cannot admit more than a mere specimen into this small work. They reject much that is clearly contained in Scripture, and profess more that is nowhere discoverable in that Divine Book.”
“Q. Give some examples of both?”
“A. They should, if the Scripture were their only rule, wash the feet of one another, according to the command of Christ, in the 13th chap. of St. John; - they should keep, not the Sunday, but the Saturday, according to the commandment, ‘Remember thou keep holy the Sabbath-day;’ for this commandment has not, in Scripture, been changed or abrogated.”
“A. Had she not such power, she could not have done that in which all modern religionists agree with her; - she could not have substituted the observance of Sunday, the first day of the week, for the observance of Saturday, the seventh day, a change for which there is no Scriptural authority.
“Q. Do you observe other necessary truths as taught by the Church, not clearly laid down in Scripture?
Today the whole world wonders after the Vatican (Rev 13:3) and so few “follow the Lamb whithersoever he goeth” (Rev 14:4). Jesus predicted this when he said, “Narrow is the way, which leadeth unto life, and few there be that find it” Matt 7:14.
“I considered the horns, and there came up among them another little horn, before whom there were three of the first horns plucked up by the roots.” Dan 7:8.
This little horn “shall speak great words against the most High, and shall wear out the saints of the most High, and think to change times and laws” verse 25.
What was this little horn power?
In Daniel 7 this little horn power lasts for 3½ times (verse 25). In the book of Revelation we see it again. “And there was given unto him a mouth speaking great things and blasphemies…against God.” Rev 13:5. “And it was given unto him to make war with the saints, and to overcome them” verse 7. This is obviously the same power that opposes God and His saints, His holy people. “And power was given unto him to continue forty and two months” verse 5. This is another clue equal to the 3½ times of Daniel 7.
3½ times of 360 days each is 1260.
But this power that comes after “the falling away” of 2Thes 2:3 “opposes and exalts himself above all that is called God, or that is worshiped so that he as God sits in the temple of God, showing himself that he is God” verse 4. This is just amazing!
Who would dare challenge the God of the universe
with such audacity!
“Thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north: I will ascend above the heights of the clouds; I will be like the most High” Isaiah 14:13,14. I will be God!
At the very beginning of her rise to power, the church declared war on those who refused to follow her new creed. Three Christian nations were her target: the Ostrogoths from the Balkans, the Carthagenians in North Africa, and the Heruli of Italy—all rejected Rome’s trinity. And it was this that drew the dragon’s fire.
The Heruli were first to fall in 493. Next, the Carthagenians were subdued by the Roman army in 533, and finally the Ostrogoths in 538. The Christians who believed Jesus to be the true Son of the one true God were exterminated by the little horn power of papal Rome because they refused to accept “a god whom his fathers knew not” Dan 11:38.