Theophilus of Edessa (ca. 695 - 785 AD) played a role in the most transformative events of the Middle East between Muhammad and the Crusades. A Christian and chief astrologer for the Caliph al-Mahdi, Theophilus was a full-time military astrologer, actively advising 'Abbasid operations and adapting Dorotheus of Sidon to the needs of generals and kings. Much of his life was spent in the field, unlike better-known astrologers like Masha'allah.This first translation of his astrological works showcases works on military questions and inceptions, mundane ingresses and Lots, weather, everyday elections, and much more, especially his use of Dorotheus and Rhetorius.