Develtos was ceded to Tsar Simeon I in the Treaty of 896, and designated as the site where the annual tribute to the Bulgarians was to be delivered. Simeon I launched his campaign against Constantinople by way of Develtos in the summer of 913, thus beginning the War of 913-927. As per the stipulations of the Treaty of 927, Tsar Peter I relinquished control of the city to Emperor Romanos I Lekapenos, and Develtos became part of the theme of Thrace.