The Apostolic Church of Jesus Christ never made it out of the First Century intact. Much of the content of the Epistles were written in response to the false teaching that had already crept into the Church.
The Book of I John was written to combat the proto-gnosticism that was prevalent in the Church. The subsequent centuries were very much dominated by heresy and the visible, vibrant, powerful Church you continually speak of is absent from the pages of history.
There has of course always existed those true believers that never wavered in faith and practice. But the fact is the true people of God are Pentecostal in experience and Apostolic in doctrine. This is what Jesus taught and led His disciples to be. The true worshippers worship him in spirit and in truth. The Foundation of Truth (Eph2:20) is the Oneness of God and the absolute Deity of Jesus Christ. (
Isaiah 43:10,
John 8:24). There has always existed a remnant of the true people of God. But "remnant" hardly meets your description of your historical Church. Where is the documentation, the proof of this mysterious "powerful" Church? It simply isn't there.
Oh, make no mistake, there have been Oneness believers throughout Church History. But they were generally treated as heretics by the visible institutional Church and thousands were killed for their denial of the trinity. The "anathema clause" of the Athanasian Creed was enforced often and with vigor.
"The Reformation produced many who opposed the doctrine of the trinity in favor of Oneness beliefs. One prominent antitrinitarian at the time of the Reformation was Michael Servetus (1511-53), an eminent physician from Spain. He had only a few followers, although some historians consider him to be a motivating force for the development of Unitarianism.
However, he definitely was not Unitarian, for he acknowledged Jesus as God. The following description of him clearly indicates that he was a Oneness believer: “The denial by Servetus of the tripersonality of the Godhead and the eternality of the Son, along with his anabaptism, made his system abhorrent to Catholics and Protestants alike, in spite of his intense Biblicism, his passionate devotion to the person of Christ, and his Christocentric scheme of the universe.”
Servetus wrote, “There is no other person of God but Christ. . . . The entire Godhead of the Father is in him.”Sound familiar? Servetus went so far as to call the doctrine of the trinity a three-headed monster. He believed it necessarily led to polytheism and was a delusion from the devil. He also believed that because the church accepted trinitarianism, God allowed it to come under the rule of the papacy and so to lose Christ. He could not understand why the Protestants would come out of Catholicism but still insist upon retaining the nonbiblical and man-made doctrine of the trinity.
Servetus was burned at the stake in 1553 for his beliefs, with the approval of John Calvin (although Calvin would have rather had him beheaded)." (David Bernard, The Oneness of God, Ch 10).
The whole of Church History since the time of the Reformation has been the gradual rediscovery and restoration of lost truth. 1913 was simply one more link in the chain of the promised restoration of the True Church of Jesus Christ.