Eusebius of Caesarea (ca. 265-ca.339) is known as the "father of church history." He took part in the debates of his time, leaning towards the Arian position regarding the nature of the Son, Origen's view on subordination, and distrusted the teaching of Sabellianism. After being charged for the heresy of his Arian inclinations, Eusebius adopted the Nicene understanding of Jesus and rejected Arius.
He was Constantine's advisor and was also a productive writer. His writing is considered the best source of early Christian history, due to the information it contains on events and people that is not recorded elsewhere.