For 10 points, name this grandson of Charles Martel and Carolingian ruler who greatly expanded the Frankish empire.
This ruler set up a system of authority and law in his namesake Capitulary. A biography of this ruler was written by Einhard. This ruler originally split lands with his brother Carloman after the death of his father, Pepin the Short. This man was unexpectedly crowned while kneeling to pray in St. Peter's Basilica on Christmas by Pope Leo III, becoming by that action "Emperor of the Romans" in the year 800. For 10 points, name this grandson of Charles Martel and Carolingian ruler who greatly expanded the Frankish empire.
This ruler set up a system of authority and law in his namesake Capitulary.
{Charlemagne} [or Charles I; or Charles the {Great}; or Charles le {Grand}; or Karl {der Grosse}