What is Trinitarianism in the Church Fathers?

Whether the earliest Church Fathers believed in the Trinity is a subject for debate. Some of the evidence used to support an early belief in the Trinity are triadic statements from the New Testament and the Church Fathers. The view that the Son was 'of the substance of the Father, God of God...very God of very God' was formally ratified at the First Council of Nicaea in 325 AD. The Holy Spirit was included at the First Council of Constantinople , where the relationship between the Father, Son and Holy Spirit as one substance and three co-equal persons was formally ratified.