Leo III the Isaurian

Born around 685, Leo rose through Byzantine ranks during an empire in freefall: between 695 and 717, emperors cycled through power while the seventh century's territorial hemorrhaging continued. He took the throne in 717 and stabilized what had seemed ungovernable, halting the Twenty Years' Anarchy. Then he turned to the Umayyad forces pressing at the gates and repelled them, securing borders that had bled for decades. But his reign is remembered less for military success than for what came next: he forbade the veneration of icons, igniting a religious convulsion that would define Byzantine politics long after his death in 741.