[3] Leo III was fluent in Arabic,[4] possibly as a native language,[5] and was described by Theophanes the Confessor as "the Saracen-minded," although there is very little evidence that he was directly influenced by Islam.

[6] After the victory of Justinian II, Konon was dispatched on a diplomatic mission to Alania and Lazica to organize an alliance against the Umayyad caliphate under al-Walid I.

On his deposition, Konon joined with his colleague Artabasdos, the stratēgos of the Armeniac Theme, in conspiring to overthrow the new Emperor Theodosius III, ostensibly in support of Anastasius.

[15] The following year saw the deposed Emperor Anastasius II raise an army and attempt to retake the throne, but he was captured and executed by Leo's government.

[16] Umayyad attacks under Caliph Hisham ibn Abd al-Malik continued in the form of yearly raids in eastern and central Asia Minor (see hatched area in figure), which affected communications, commerce and agricultural production.

[23][24] The Empire of the eighth century was characterized by ruralization and depopulation, which along with the Arab invasions motivated Leo to undertake intense centralization and militarization, particularly involving the many fortresses and walls in towns such as Nicaea and Padyandus.

In 730, Patriarch Germanus opted to resign rather than subscribe to iconoclasm; Leo replaced him with Anastasius,[32] who willingly sided with the Emperor on the question of icons.

On the basis of Patriarch Germanus' letters read at the 787 Second Council of Nicaea, which state that the bishops Constantine of Nakoleia and Thomas of Claudiopolis had forbidden the veneration of icons even before 730, some scholars argue that the alleged aniconism of the eastern part of the Empire, Leo's place of origin, motivated his policies.

[39] Others have discussed the mutual influence of Muslim and Byzantine iconoclasm, noting that Caliph Yazid II had issued an iconoclastic edict, also targeting his Christian subjects, already in 721.

Thus, Auzépy says, the banning of the veneration of images was fundamentally a rejection of idolatry in order to ensure the survival of the Christian people of the Empire, a decision which was apparently vindicated by the abatement of the Arab and Bulgar threat during Leo's reign.

[41] Some scholars, such as Leslie Brubaker and John Haldon, doubt whether there was any active imperial involvement in iconoclasm at all, proposing instead that Leo made a qualified critique of the use of images in public spaces, likely leading to the adoption of a somewhat iconoclastic attitude among the clergy in the late 730s or early 740s.

[43] Brubaker and Haldon support this hypothesis by pointing to the absence of any reports of iconoclasm in several contemporary accounts, including those of Willibald, who travelled to Nicaea from 727 to 729, Germanus and even John of Damascus.

[44] Brubaker and Haldon attribute a more moderate iconoclasm to Leo, "It is quite possible that Leo did attempt to restrict the public display of certain types of image and to remove them from certain places in churches (near the altar and in the apse, for example) to avoid their receiving the honour due to God alone", confirming this conclusion with the writings of Germanus and John of Damascus which appear to describe a kind of initial or moderate stage of iconoclasm.

[45] Leo reformed the silention, a type of restricted council instituted by Justinian I, transforming it into a special assembly in the Great Palace of Constantinople, in which the emperor would announce a solemn decision.

[49] Leo's prologue to the Ecloga sets out his conception of law as requiring ethical significance founded upon God's will and divinely-sanctioned imperial authority.

[55] In response to the catastrophic Twenty Years' Anarchy, Leo, and his son Constantine V in emulation, fundamentally changed the formula of imperial survival as established by Justinian I.

This autocratic renewal of imperial authority was motivated by justice and spiritual welfare, leading to the denunciation and eventual destruction of images deemed to be "idolatrous".

Modern assessment of the reign of Leo as well as that of his son is that it was a period of violence which saw the Empire's rescue from destruction, within a context of extensive domestic policy reform.

[60][61] His personal knowledge of the geography of the foothills of the Taurus Mountains helped in the countering of Arab incursions mainly in the latter part of his reign, as was especially signified in the Battle of Akroinon—a crucial victory for Leo which had changed the tide of the Arab–Byzantine wars in the favour of Rome for the next 350 years.

[63] In 1573, a translation of John of Damascus' attack on Leo III was published, under the title Apologie divisée en trois livres contre Léon Isaure, triggering religious controversy.