Socrates Scholasticus: Ecclesiastical History

The Christological monogram (X and P, chi-rho), the first two letters of Christ in Greek (ΧΡΙΣΤΟΣ): the symbol instituted by Emperor Constantine I for his military standards (vexillum) and a Christian symbol of eternal life and triumph through Christ. 4th-century CE, marble, Pius-Christian Museum, Vatican City.

History of the Catholic Church from accession of Constantine (A.D. 306) to the seventeenth consulship of Theodosius the Younger (A.D. 419). Written with the intention to serve as a continuation of Eusebius Pamphili’s Ecclesiastical History. Completed around 439 A.D., it provides an invaluable and intimate portrait of the early Byzantine Church and culture. Image above links to Schaff and Wace edition. ISBN recommendation: 0-8028-8116-5