Eusebius of Caesarea stands at one of the most decisive thresholds in Christian history, a figure whose life and work bridge the turbulent centuries of persecution and the dawning age of imperial favor. To call him the "Father of Church History" is not merely to acknowledge his literary achievement but to recognize the unique position he occupies as a witness to the Church's transition from the Apostolic memory to the Constantinian peace. His writings preserve voices, documents, traditions, and testimonies that would otherwise have vanished in the fires of persecution or the slow erosion of time. Yet Eusebius is more than a chronicler. He is a custodian of the Sacred Text at a moment when the Church was forced to define, defend, and disseminate the Scriptures that would become the heart of Christian identity. His work is therefore indispensable for understanding how the canon of the New Testament emerged, how the early Church discerned authentic apostolic teaching, and how the written Word was preserved through the most violent assaults against it.