In 610 Sergius became patriarch of Constantinople and later the same year crowned Heraclius as emperor (r. 610–641). Sergius would remain central to imperial religious policy until his death in 638. These were tumultuous years, as the empire faced incursions from Avars to the northwest and, more threateningly, from the Persian shah Khusro II to the east. After Khusro’s initial success, including the capture of Jerusalem and the True Cross, Heraclius and his allies defeated the shah in 627 and restored the True Cross in 630. In the coming twelve years, however, the empire would lose Syria, Palestine, and Egypt to a new invader, the Arab tribes. Internally, Christians of the eastern Mediterranean were divided. In 638 Sergius penned a fateful Ekthesis or “exposition” of faith, in the hopes of ending certain disputes among Chalcedonians. The Ekthesis, issued in the name of Heraclius, repeats the prohibition initially issued in 633 in the Psēphos on teaching either a single or two activities in Christ (the positions known, respectively, as monoenergism and dyoenergism).