Once a patriarch, Cyrus continued trying to unite Miaphysites and Chalcedonians around monoenergism, now evolving into monotheletism, the idea of one will. In a synod held at Alexandria in June 633, he proposed what is known as the Pact of Union, plèrophoria or "Satisfactio", an agreement in nine articles, the seventh of which is a bold assertion of monothelitism. The Miaphysites welcomed the agreement but remarked that Chalcedon was coming to them, not they to Chalcedon. Thousands of clergy, soldiers and ordinary people converted with Cyrus away from the miaphysite position at this time, but the change did not last. It was hoped that Pope Honorius I would be won over to the monothelete position. Cyrus attended another synod at Cyprus under Arkadios II in 636 along with 45 other senior clergy, at which he served as moderator and permitted Monothelite opponents to submit their case to the Emperor. When Cyrus received the Emperor's Monothelite response, the Ecthesis, Cyrus signed it in 637. Ultimately the monothelete compromise proved ineffective, as it was condemned at the Lateran Council of 649 and soon fell into discredit under the contemptuous name of.
Military prefect
When Caliph Umar the Great's general, 'Amr ibn al-'As known to the Romans as Amru, threatened the Prefecture of Egypt, Cyrus was made prefect and entrusted with the conduct of the war. Certain humiliating stipulations, to which he subscribed for the sake of peace, angered his imperial master so much that he was recalled and harshly accused of connivance with the Rashidun Caliphate; however, he was soon restored to his former authority, owing to the impending siege of Alexandria, but could not avert the fall of the great city in 640. He signed a peace treaty that surrendered Alexandria and Egypt on 8 November 641 before dying in 642.
Writings
From Cyrus there are three letters to Sergius and the "Satisfactio", all preserved in the acts of the Roman Synod of the Lateran and of the Sixth Œcumenical Council. The first letter is an acceptation of the Ecthesis; in the second Cyrus describes his perplexity between Pope Leo and Sergius; the conversion of the Theodosians is narrated in the third. The seventh article of the "Satisfactio" — the others are irrelevant — reads thus: "The one and same Christ, the Son, performs the works proper to God and to man by one theandric operation according to St. Dionysius". Cyrus' chief opponents, St. Sophronius, died in 638, and St. Maximus, died in 662, reproached him for falsifying the then much-respected text of Dionysius and substituting for . They showed, moreover, the inanity of his claim to the support of the Fathers, and explained how the Divine and human natures of Christ, sometimes styled one, because they belong to the same person and work in perfect harmony, can no more by physically identified than the natures from which they proceed. Historians are not agreed as to how Cyrus came by this. Some think that he was, from the outset, a Monophysite at heart. Others, with more reason, hold that he was led to this belief by Sergius and Heraclius. Cyrus was posthumously condemned as a heretic in the Lateran Council of 649 and in 680 at the Third Ecumenical Council of Constantinople.
