In 1258, the Sicilians took possession of the island of Corfu and the Albanian coast, from Dyrrhachium to Valona and Buthrotum and as far inland as Berat. This gave Manfred a strategically vital beachhead in the Balkans, controlling the western terminus of the great Via Egnatia, the main overland route to Constantinople. Already in the 11th and 12th centuries, the same area had been the target of the Normans of southern Italy in their attacks on the Empire. After overthrowing Manfred, in the Treaty of Viterbo (1267) Charles secured his recognition as Manfred's heir. In 1272, the Latin notables who had held the fortresses of Valona, Kanina, and Berat for Manfred surrendered them to Charles, and soon afterwards Charles's troops took Dyrrhachium too. Having secured the support of many Albanian chieftains, Charles proclaimed the establishment of the Kingdom of Albania in the same year.