Few years after the dissolution of Arbanon, Charles of Anjou concluded an agreement with the Albanian rulers, promising to protect them and their ancient liberties. In 1272, he established the Kingdom of Albania and conquered regions back from the Despotate of Epirus. The kingdom claimed all of central Albania territory from Dyrrhachium along the Adriatic Sea coast down to Butrint. A catholic political structure was a basis for the papal plans of spreading Catholicism in the Balkan Peninsula. This plan found also the support of Helen of Anjou, a cousin of Charles of Anjou. Around 30 Catholic churches and monasteries were built during her rule mainly in northern Albania. Internal power struggles within the Byzantine Empire in the 14th century enabled Serbs' most powerful medieval ruler, Stefan Dusan, to establish a short-lived empire that included all of Albania except Durrës. In 1367, various Albanian rulers established the Despotate of Arta. During that time, several Albanian principalities were created, notably the Principality of Albania, Principality of Kastrioti, Lordship of Berat and Principality of Dukagjini. In the first half of the 15th century, the Ottoman Empire invaded most of Albania, and the League of Lezhë was held under Skanderbeg as a ruler, who became the national hero of the Albanian medieval history.