Leo III (ca. 680-741), called the Isaurian, was Byzantine emperor from 717 to 741. He rescued the empire from disaster and began the containment of the Arabs' eastern advance. He also initiated the controversial Iconoclastic movement.

Leo was born in Germanicea in northern Syria, but his family was resettled in Thrace by one of the population movements of the last Heraclian emperor, Justinian II, during his initial regime (685-695). Leo attracted this sovereign's attention during his second regime (705-711) and then won a reputation for daring exploits during the chaos of the Heraclian dynasty's collapse. Under the insecure Anastasius II (713-715) he was advanced to command of the Anatolikon Theme, one of the military provinces of Asia Minor. Rivalries between troop units of the various themes produced rebellions and instability, encouraging Leo's own ambitions. Leo formed a coalition with another thematic commander, Artavasdus, who became his son-in-law. Evading Arab attacks...