Background After the
Umayyad Caliphate was repelled at the
first Arab siege of Constantinople (674–678), the Arabs and
Byzantines experienced a period of peace between each other. Hostilities were resumed by Byzantine Emperor
Justinian II (), resulting in a string of Arab victories. As a consequence, the Byzantines lost control over
Armenia and the
Caucasian principalities, and the Arabs gradually encroached upon the Byzantine borderlands. Annually, generals from the Caliphate would launch raids into Byzantine territory, seizing fortresses and towns. After 712, the defenses of the Byzantine Empire weakened, as Arab raids penetrated deeper into Byzantine
Asia Minor, and Byzantine response to these raids became less common; much of the frontier became depopulated, as the inhabitants were either killed, enslaved, or driven away. A result of this was that many frontier forts, especially in
Cilicia, were gradually abandoned. The success of these raids emboldened the Arabs, who prepared for a second assault against
Constantinople as early as the reign of Caliph
al-Walid I (). After his death, his successor,
Sulayman () continued planning the campaign, Sulayman began assembling his forces in late 716, on the plain of
Dabiq, north of
Aleppo, entrusting the command of these forces to his brother,
Maslama ibn Abd al-Malik. The
Slavs and
Bulgars also formed a growing threat to the northern frontier of the Byzantine Empire, threatening Byzantine control in
the Balkans. During the rule of Byzantine Emperor
Philippicus (), in 712, the Bulgarians under Khan
Tervel advanced as far as the walls of Constantinople itself, plundering the surrounding country, including villas and estates near the capital, where the Byzantine elites often summered. Theodosius came to power during a period called the
Twenty Years' Anarchy, defined by struggles between the emperors and the elites, and political instability, with a rapid succession of emperors. 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. The Twenty Years' Anarchy began when Emperor Justinian II was overthrown by
Leontius () in 695, ending the
Heraclian dynasty, which had retained power for eighty years. During this period of anarchy, seven different emperors took the throne, including a restored Justinian for a time. The modern historian
Romilly Jenkins states that between 695 and 717 the only competent emperors were
Tiberius III () and
Anastasius II (). The crisis was ended by Emperor
Leo III (), who overthrew Theodosius, and whose dynasty reigned for 85 years.
Rise to the throne Sulayman's preparations, including his construction of a war fleet, were quickly noticed by the Byzantine Empire. Emperor Anastasius II began making preparations to defend against this new onslaught. 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, 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. It was there that the troops of the
Opsician Theme mutinied against their commander,
John the Deacon, killing him before sailing for
Adramyttium, in southwestern Asia Minor, and there declared Theodosius, a tax collector, as Emperor Theodosius III. The
Zuqnin Chronicle states that Theodosius ruled under the
regnal name Constantine, his full name being "Theodosius Constantinus". The historian
J. B. 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.
Graham Sumner, a
Byzantologist, suggests that Theodosius might be the same person as
Theodosius, the son of Emperor Tiberius III, therefore explaining why he might have been chosen by the troops, as he would have legitimacy from his father, himself made emperor by a naval revolt. Theodosius, the son of Tiberius, was
bishop of Ephesus by , 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. 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. Cyril Mango proposed that it was actually Theodosius III's son who became bishop, rather than the son of Tiberius. Theodosius was allegedly unwilling to be emperor and according to Theophanes: He was acclaimed as Emperor Theodosius III by the troops of the Opsician Theme at
Adramyttium in May 715. Anastasius led his army into
Bithynia in the Opsician Theme to crush the rebellion. Rather than remaining to fight Anastasius, Theodosius led his fleet to
Chrysopolis, across the
Bosporus from Constantinople. 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. Anastasius remained at
Nicaea for several months, before finally agreeing to abdicate and retire to a monastery.
Reign One of Theodosius's first acts as emperor was to reinstate the depiction of the
Sixth Ecumenical Synod in the
Great Palace of Constantinople, which Emperor
Philippicus Bardanes had removed, earning himself the epithet of "Orthodox" in the
Liber Pontificalis for this action. 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. Thus he was not recognized as legitimate by the
Anatolic and the
Armeniac Themes, under their respective (generals)
Leo the Isaurian and
Artabasdos. Although they had not taken any action to prevent the overthrowal of Anastasius, they took issue with Theodosius's ascension, and Leo proclaimed himself Byzantine emperor in the summer of 716. He also sought the support of the Arabs, who viewed the Byzantine disunity as advantageous, and thought the confusion would weaken the Byzantine Empire and make it easier to take Constantinople. Theodosius negotiated a treaty with the
Bulgarian khan Tervel (), likely to secure his support against an imminent Arab attack. The treaty fixed the border between the Byzantine Empire and the
Bulgarian Empire at
Thrace, ceding the
Zagoria region to the Bulgarians, as well as stipulating the payment of tribute to the Bulgarians, the return of fugitives, and some trade agreements. Around this time, Sulayman had begun advancing into Byzantine territory, laying siege to
Amorium, and a separate force entered
Cappadocia. Negotiations with Leo led them to withdraw. Leo began to march his troops to Constantinople soon after declaring himself emperor, first capturing
Nicomedia, where he found and captured, among other officials, Theodosius's son, and then marched to Chrysopolis. After his son was captured, Theodosius, taking the advice of
Patriarch Germanus and the Byzantine Senate, agreed to abdicate and recognize Leo as emperor. Bury states that the elite of Constantinople, who might otherwise have sided with the inoffensive Theodosius, who would be unlikely to politically weaken them, sided with Leo, as Theodosius was not competent enough to deal with the Arab threat. He further states that the meeting of the Patriarch, senate, and chief officials, which chose Leo over Theodosius, was done with the knowledge and consent of Theodosius himself, who accepted the decision. 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. Leo entered Constantinople and definitively seized power on 25 March 717, allowing Theodosius and his son, also named Theodosius, to retire to a monastery as monks. After his retirement to a monastery, Theodosius might have become the bishop of Ephesus, if he was the same person as Theodosius, son of Tiberius, in , and, if he is the same, died on 24 July 754 according to Sumner. Either he or his son is buried in the
Church of St. Philip in
Ephesus. Little is known of the reign of Theodosius III. == References ==