In the Treaty of Verdun of 843 the three surviving sons of Louis the Pious, Charlemagne's grandsons, divide his territories, the Carolingian Empire, into three kingdoms.

Though often presented as the beginning of a devolution or dissolution of Charlemagne's unitary empire, it in fact reflects the continued adherence to the Germanic, and therefore Frankish, idea of a partible or divisible inheritance rather than primogeniture, inheritance by the eldest son.When Louis the Pious died in 840, the eldest son, Lothair I, claims overlordship over his brothers' kingdoms and supports the claim of his nephew Pepin II as king of Aquitaine.

After his brothers Louis the German and Charles the Bald defeat his forces at the Battle of Fontenay (841) and seal their alliance with the Oath of Strasbourg (842), Lothair is willing to negotiate.Each of the brothers is already established in one kingdom - Lothair in Italy, Louis the German in Bavaria, and Charles the Bald in Aquitaine.