The First Council of Nicaea in 325 AD. This is when Bishops (mostly Eastern) around the world came to discuss and find an Orthodox view for Christology(among other topics)and make the step towards rejecting heresy. What was meant by the term "Jesus is God," people had different views, you could say Jesus is God but what was meant by that? We see this today through the  Unitarians and Trinitarians, Apostolic for example. 

 Many Christians were thinking like Dr.Arius and held his view before the Council, other Bishops felt as if people were being tricked out of salvation through Arianism and needed to take a vote. Look at the spelling of Unitarian and Trinitarian, you see "Arian" included because of this council. 

 The Arian controversy 
 Arianism; Jesus is "a god," created as a lower case divinity, an angelic level of creation.
Church of Alexandria; Jesus was begotten and not created, co-eternal and existent, coequal to the father.

 Emperor Constantine had summoned up the Council as several Synods was concerned over Arius teachings being "heretical" and spreading. Council conclusion; "Christ was just as powerful" and eternal, equal in all things. The record shows; this vote at the council was highly against Arians.  

 The Modern Mixup
 The Way International Splinters was taught for years; the Council of Nicaea in 325 is when Bishops voted on the Trinity, and when the Canon come about. Dan Brown taught this in his fictional book; Da Vici Code, Wierwille appears to have mixed it up before Dan. This is totally false information. Nicaea was not about the Holy Spirit at all, but Christology "the son of God."  First Council of Constantinople 381 C.E. is when Trinity became established to reject heresy, and the canon had nothing to do with Nicaea at all. 

 Christ was God unto early Christians
 These men already agreed "Christ was divine," but had different viewpoints on Christology. Arius even thought; Jesus was divine, so did mostly everyone else with different views about the deity of Christ. Going to the very start of Christianity mostly everyone was an Adoptionist, several Roman leaders were modalists in the second century and Tertullian was a Trinitarian in 155-240 AD, Marcion Christology with two Gods.

 Adoptionist Christology was the earliest and most dominant view of all others, Mark is the very first canonical gospel and is bringing forth an Adoptionist view of Jesus at his Baptism. Luke and Matthew at the birth through Mary.  
             

Mark 1:9-11English Standard Version (ESV)

The Baptism of Jesus

9 In those days Jesus came from Nazareth of Galilee and was baptized by John in the Jordan.  And when he came up out of the water, immediately he saw the heavens being torn open and the Spirit descending on him like a dove. And a voice came from heaven, “You are my beloved Son; with you I am well pleased.”

       
Acts 13:33 King James Bible
  "God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee."
      
King James Bible Psalm 2:7
    "I will declare the decree: the LORD hath said unto me, Thou art my Son; this day have I begotten thee."

The adoptionist view appears in the book of acts.
 
Acts 2:36  King James Bible
    "Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ."

Hebrews 1;5
   "For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son? "