 After King Pepin had made several attempts to conquer Venice on the Adriatic coast, his father Emperor Charlemagne under the 812 Treaty of Aix-la-Chapelle finally recognised the formal Byzantine control over the city along with Istria, at least its western coast.After this, it falls into obscurity, but perhaps the Byzantines never succeeded in re-establishing their government in the returned territories, if they were actually handed over.The remaining parts of Istria were probably eventually just re-integrated into the Carolingian duchy of Friuli.