Louis the Pious

Sole surviving legitimate son of Charlemagne, inheriting the entire empire intact. His repeated attempts to redivide the realm among his sons by two marriages produced civil war: his sons by his first marriage rebelled twice, briefly deposing him in 833 in the so-called Field of Lies. He is the last Carolingian to rule the empire whole; his death triggered the war that produced the Treaty of Verdun.