Constantine and Charlemagne are arguably two of the greatest Christian emperors to ever rule the Roman Empire. While these men reigned almost five centuries apart, they shared certain ambitions and personality traits that simultaneously made them effective leaders and caused them significant problems. Neither Constantine nor Charlemagne was born "destined" to be an emperor. Although Constantine's father rose to the rank of Augustus, Diocletian's tetrarchy was not set up to facilitate dynastic rule. Charlemagne, on the other hand, was born into a royal family—but one whose members had begun ruling as mere "mayors of the palace," evolved into kings, and would never have imagined themselves becoming "emperors" before the days of Charlemagne himself.
