Leo entered Constantinople and definitively seized power on 25 March 717, allowing Theodosius and his son to retire to a monastery.

The nobles of this time were often natives of Asia Minor, and rarely had a strong agenda beyond preventing the emperors from growing stronger and disrupting the status quo.

This included sending the patrician and urban prefect, Daniel of Sinope, to spy on the Arabs, under the pretense of a diplomatic embassy, as well as shoring up the defences of Constantinople,[17][18][19] and strengthening the Byzantine navy.

The 9th-century Byzantine historian Theophanes states that in early 715 Anastasius II had commanded the navy to gather at Rhodes to then advance to Phoenix.

Bury suggests that he was selected at random for little more than the fact that he already had an imperial-sounding name, was inoffensive, obscure but respectable, and could easily be controlled by the Opsicians.

Theodosius, the son of Tiberius, was bishop of Ephesus by c. 729, and held this position until his death, sometime around 24 July 754, and was a leading figure of the iconoclastic Council of Hieria in 754.

[26] Byzantine historians Cyril Mango and Roger Scott do not view this theory as likely, as it would mean that Theodosius lived for thirty more years after his abdication.

From Chrysopolis, he launched a six-month-long siege of Constantinople, before supporters within the capital managed to open the gates for him, allowing him to seize the city in November 715.

[27][b] Theodosius, whom Byzantine sources convey as being both unwilling and incapable, was viewed by many of his subjects as a puppet emperor of the troops of the Opsician Theme.

[33][34] Although they had not taken any action to prevent the overthrowal of Anastasius, they took issue with Theodosius' ascension, and Leo proclaimed himself Byzantine emperor in the summer of 716.

[27] Around this time, Sulayman had begun advancing into Byzantine territory, laying siege to Amorium, and a separate force entered Cappadocia.

After his son was captured, Theodosius, taking the advice of Patriarch Germanus and the Byzantine Senate, agreed to abdicate and recognize Leo as emperor.

[43] Bury postulates that, without the threat of the Arabs, it is possible that Theodosius may have retained power, and a succession of nominal emperors might have followed him, controlled by court officials and the elites.