This article is one in a series on the history of the Church - you are currently on the topic that is in bold:
The following Christians all believed in the doctrine of the Trinity
If as William Branham said: "You put Him a third person, second person, or any other person besides God, you're lost. "Except you believe that I am He, you will die in your sins." A revelation!
According to William Branham, these Christians were required to believe satanic doctrine in order to be saved.
Polycarp, d. ~156 A.D.
With Clement of Rome and Ignatius of Antioch, Polycarp is regarded as one of three chief Apostolic Fathers. A letter of his to the Philippians has been preserved, and is described by Irenaeus as a "forceful epistle". Polycarp travelled to Rome to correct heresies that had arisen in that church. He died a martyr, bound and burned at the stake, then stabbed when the fire failed to touch him.
Polycarp (martyred c. 156) wrote this Trinitarian prayer:
Irenaeus, d. ~202 A.D.
Irenaeus was bishop of Lugdunum in Gaul, which is now Lyon, France. He was a disciple of Polycarp, who was a disciple of John, who was a disciple of Jesus Christ. Irenaeus wrote extensively on the nature and unity of God, fighting bitterly against heresies and the integration of paganism into Christianity. Irenaeus also corrected the church in Rome on occasion, and testified that supernatural signs accompanied his ministry and all the believing church, including the raising of the dead, healing of the sick, prophecies, and visions.
Iranaeus clearly believed in the triunity of God as expressed in his writings and stated that:
Martin of Tours, d. 397 A.D.
Martin was born in Hungary, and became a missionary in Gaul. While little is recorded of his teachings, his piety was not disputed, and supernatural signs and wonders followed his ministry.
Patrick, d. 493 A.D.
Patrick was the nephew of St. Martine, and became a missionary to Ireland.
Columba, d. 597
Columba became a missionary to Scotland, and was known as a prophet for the mighty works that followed his ministry.
Adomnan of Iona, d., 704 A.D.
St. Adomnan was a successor to Columba as the ninth Abbot of Iona. Around 690 he wrote 'Life of Columba', which described in detail the life of his predecessor. He also drew up the 'Law of Innocents' which attempted to protect women, children and those in Holy Orders from war (a new concept at the time). Adomnan managed to get this agreement signed by the Irish Kings as well as those of the Dalriada and Picts. In his time, he was probably as important as Columba, but by so effectively establishing the historical reputation of Columba, his contribution is now somewhat overlooked. 
John Wycliffe, d. 1384
John Wycliffe is credited as the first person to give a complete translation of the Bible into English, and was the founder of the Lollard movement. Wycliffe taught justification by faith, the absolute authority of the Bible, and that the papacy was the antichrist.
Jan Huss, d. 1411
Jan Hus was excommunicated in 1411, condemned by the Council of Constance, and burned at the stake. Hus was considered a prophet by his followers, and his last words are allegedly that, "In 100 years, God will raise up a man whose calls for reform cannot be suppressed." Just over one hundred years later, Martin Luther nailed his 95 Theses of Contention to a church door in Wittenburg. Huss taught that the Church is not that hierarchy which is generally designated as Church; the Church is the entire body of those who from eternity have been predestined for salvation. Christ, not the pope, is its head.
In 1999, Pope John Paul II expressed "deep regret for the cruel death inflicted" and suggested an inquiry as to whether Hus might be cleared of heresy.
William Tyndale, d.1536
Translated the Bible into English, and was burned alive on October 6, 1536. His final words reportedly were, "Oh Lord, open the King of England's eyes". Tyndale is quoted as saying "I defy the Pope, and all his laws; and if God spares my life, I will cause the boy that drives the plow in England to know more of the Scriptures than the Pope himself!" 
Tyndale introduced the following phrases into English during his translation: "let there be light", "the powers that be", "my brother's keeper", "the salt of the earth", "a law unto themselves", "filthy lucre", "it came to pass", "gave up the ghost", "Jehovah", "Passover", "atonement", and "scapegoat".
Jacob Hutter, d. 1536
Jacob Hutter was an Anabaptist religious leader who practiced community of goods, nonviolence, and baptism of adult believers. He was tortured and burned alive on February 25, 1536. Those who followed his doctrines became known as Hutterites.
Martin Luther, d. 1546
Martin Luther was a German monk, priest, professor, theologian, and church reformer. His teachings inspired the Protestant Reformation and deeply influenced the doctrine and culture of the Lutherans and Protestants traditions, as well as the course of Western civilization.
Against those Protestants who wished to discard the language of Trinity and possibly even the doctrine itself, Luther asserted that salvation depends on belief in it. Against all deniers of the Trinitarian faith (as expounded in the Nicene Creed) Luther declared “This is the faith; so the faith teaches; here stands the faith. Naturally, I mean the Christian faith, which is grounded in Scripture. But he who does not want to believe Scripture but runs after reason—why, let him run… . This is a matter of either believing or of being lost.”
If Luther introduced any new element into the doctrine of the Trinity (besides rejecting over-rationalistic speculation) it would be an emphasis on the distinctness of the three persons. Luther was not afraid to emphasize that in the scriptural witness Father, Son, and Holy Spirit are “three different persons” even as they are of the same, identical divine essence. While admitting that no earthly illustration can possibly do justice to the heavenly reality of the Trinity, Luther used a “homely, simple illustration” to help people who struggled with the Trinity to understand it. “As a bodily son has flesh and blood and his being from his father, so the Son of God, begotten by the Father, has His being and nature from the Father from eternity.” Immediately after offering this analogy, the reformer admitted that it could not do justice to the unity of Father and Son within the eternal Godhead. However, together with other statements of the Trinity made by Luther, it illustrates his tendency to think of the three persons of God as distinct persons of love in community along the lines of Richard of St. Victor. It would be misleading to claim Luther as an example or advocate of the “social analogy” of the Trinity, but he certainly was not locked into the Augustinian psychological analogy that tended to reduce the persons of God to mere relations of origin.
Menno Simons, d. 1561
Menno Simons was an Anabaptist religious leader from Friesland. Quoted as saying "Christ is our fortress; patience our weapon of defense; the Word of God our sword. ... Iron and metal spears and swords we leave to those who, alas, regard human blood and swine’s blood of well-nigh equal value." Those who followed his doctrines became known as Mennonites.
John Bunyan, d. 1688
John Bunyan was a Christian writer and preacher. He wrote The Pilgrim's Progress, arguably the most famous published Christian allegory.
George Fox, d. 1691
George Fox was an English Dissenter and a major early figure — usually considered the founder of the Religious Society of Friends, commonly known as the Quakers. Toward the end of his life, he wrote a letter for general circulation pointing out that Abel, Noah, Abraham, Jacob, Moses and David were all keepers of sheep or cattle, and that a learned education should not therefore be seen as a qualification for ministry. 
Isaac Watts, d.1748
Isaac Watts is recognised as the "Father of English Hymnody", as he was the first prolific and popular English hymnwriter, credited with some 750 hymns.
George Whitfield, d. 1770
George Whitfield was a minister in the Church of England and one of the leaders of the Methodist movement. He travelled through America, England, Scotland, Ireland, Bermuda, Gibraltar, and The Netherlands. Benjamin Franklin calculated, by pacing the area around George Whitfield where his voice was audible while preaching, that he could indeed speak to tens of thousands of people in a single sermon.
John Wesley, d. 1791
John Wesley was an 18th-century Anglican minister and powerful field-evangelist who was an early leader in the Methodist movement. While never formally separating from the Anglican Church, John Wesley acted on his own even so far as to ordain ministers by the laying on of hands, which he had found to be a Biblical example.
In his sermon ‘On the Trinity’, Wesley is clear where he stands. The Trinity, he says, ‘enters into the very heart of Christianity: It lies at the heart of all vital religion’. He places it at the centre of worship, and of the experience of God.
Francis Asbury, d. 1816
Francis Asbury became a local preacher at 18 and was ordained at 22. In 1771 he volunteered to travel to America. When the American War of Independence broke out in 1776 he was the only Methodist minister to remain in America. 
William Carey, d. 1834
William Carey was an English Protestant missionary and Baptist minister. Carey was one of the founders of the Baptist Missionary Society. As a missionary in Serampore, India, he translated the Bible into Bengali, Sanskrit, and numerous other languages and dialects.
Adoniram Judson, d. 1850
Adniram Judson was an American Baptist missionary who translated the Bible into the Burmese language, and suffered severe persecution and imprisonment. His work inspired and equipped Ko Tha Byu, a Karen native, to become the first apostle to the Burmese. 
George Müller, d. 1898
George Muller was a Christian evangelist and coordinator of orphanages in Bristol, England, cared for a total of over 100,000 orphans in his life. He was well-known for his constant faith in God and for providing an education to the children under his care, to the point where he was accused of raising the poor above their natural station in life. In 1875, at the age of 70, he began a 17 year period of missionary travel. In that time, he preached in the United States, India, Australia, Japan, China, and nearly forty other countries. 
Dwight Lyman Moody, d. 1899
Also known as D.L. Moody, was an American evangelist, setting up Sunday Schools, and preaching accross America, and visiting China and England. 
Moody was a clear Trinitarian:
James Hudson Taylor, d. 1905
Hudson Taylor was a British Protestant Christian missionary to China, and founder of the China Inland Mission (CIM) (now OMF International).