Eusebius's account is the only surviving historical record of the Church during its crucial first 300 years Bishop Eusebius a learned scholar who lived most of his life in Caesarea in Palestine broke new ground in writing the History & provided a model for all later ecclesiastical historians In tracing the history of the Church from the time of Christ to the Great Persecution at the beginning of the fourth century & ending with the conversion of the Emperor Constantine his aim was to show the purity & continuity of the doctrinal tradition of Christianity & its struggle against persecutors & heretics