Cyrus entered Egyptian politics as the representative of Heraclius’s attempt to restore religious unity. In 631 he was appointed simultaneously patriarch and civil governor, a combination that embodied the Byzantine integration of ecclesiastical and state authority. His task was to persuade Egyptian Christians to accept the Monergist compromise developed by Heraclius and his advisers.

Cyrus possessed energy and courage, but he was also portrayed as harsh and merciless toward opponents. The Copts regarded him as a foreign Caucasian who had displaced their own patriarch, Benjamin. His correspondence further suggested that he was willing to proclaim the orthodoxy of the Tome of Leo, making Monophysite confidence in the compromise even more difficult.

After initial success, Cyrus failed to convince most monks that Monergism could be accepted without an imperial denunciation of Chalcedon. He then turned from persuasion to force between 635 and 641. This policy eroded the loyalty that remained toward Heraclius, and Cyrus ultimately capitulated at Alexandria in September 641, bringing the immediate political and military crisis to an end.