Eusebius Pamphilus Father of the A.D. Church History.

Eusebius used the resources at his disposal to focus attention on the church he saw as the true descendant of first-century Christianity. 

Critics of Eusebius accuse him of lacking critical judgment and literary style. In his day, however, he was highly regarded both as a Catholic bishop and as a historian by many in high places, including the bishop of Rome and the emperor Constantine. This allowed him access to the imperial archives and the opportunity to study a wide range of documents, many of considerable antiquity. Because much, if not most, of this material is now no longer extant, the service rendered by Eusebius to later generations lies in his extensive quotations from such works.