Charlemagne died in 814, leaving the empire he built to his son Louis the Pious. Louis had three elder sons: Lothair, Pepin of Aquitaine, and Louis the German. Then, with another wife, he sired Charles the Bald. While Louis was alive, the older princes forced their father to abdicate, only to have him regain his power and punish court members who were disloyal to him. Pepin died. Louis died. The succession problem remained. Open civil war broke out as Louis Jr. and Charles allied against Lothair, who had claimed the throne for himself. For years, armies clashed in bloody battles. In 843, the Treaty of Verdun ended the conflict, carving the empire into three kingdoms that would lay the groundwork for later political maps of Europe. Amid all the Carolingian squabbles, popes, cardinals, kings, fathers, sons, brothers, and supporters regularly swore official sacred oaths to one another, just to be disregarded in favor of personal ambition.