belonged. The Count of the Opsicians probably retained authority over civil administration and local defence, while the Aegean theme was solely responsible for equipping ships and raising the men for fleets from these areas. A similar procedure existed in the theme of Samos as well. This view is strengthened by the fact that the Opsicians, and especially the Slavs (Sklabesianoi) forcefully settled by the Empire in the Opsician Theme, are attested serving as marines in the 10th century. According to Emperor Constantine VII Porphyrogennetos (r. 913–959), in the early 10th century the theme included Lesbos (the seat of the strategos), Lemnos, Imbros and Tenedos, Chios (later transferred to Samos), the Sporades and the Cyclades. According to Hélène Ahrweiler, the Cyclades were probably transferred to the Aegean theme when the Dodekanesos/Kolpos naval command was broken up and the theme of Samos established from it in the late 9th century. In 911, the forces of the naval theme of the Aegean are recorded as being 2,610 oarsmen and 400 marines. The province survived until the late 10th/early 11th century, when it became progressively split up into smaller commands. As the Cyclades and Sporades, Chios and the region of Abydos acquired their own strategoi, the theme of the Aegean became a purely civil province comprising only the coasts of the Propontis and the region around Constantinople. By the late 11th century, what remained of the old thematic fleet was incorporated into the unified imperial navy at Constantinople, under the command of the megas doux. Thereafter, some time in the 12th century, the theme of the Aegean seems to have been fused with the Opsician theme into a single province, as attested in the Partitio terrarum imperii Romaniae in 1204. The theme ceased to exist after the dissolution of the Byzantine Empire by the Fourth Crusade in 1204. References Sources Themes of the Byzantine Empire Medieval Aegean Sea Byzantine navy States and territories established in the 840s 843 establishments