Aegean Sea ( theme ) The Theme of the Aegean Sea ( , " thema tou Aigaiou Pelagous " ) was a Byzantine province in the northern Aegean Sea , established in the mid - 9th century . As one of the Byzantine Empire ' s three dedicated naval themes ( Greek : ) , it served chiefly to provide ships and troops for the Byzantine navy , but also served as a civil administrative circumscription . History . The theme has its origins in the late antique civil province of the islands ( ; ) , which encompassed the islands of the southeastern and eastern Aegean up to Tenedos . The term " " Aigaion Pelagos " " appears for the first time as an administrative circumscription in the early 8th century , when seals of several of its " kommerkiarioi " ( customs officials ) are attested . One seal , dated to 721 / 722 , even refers to an official in charge of all the Greek islands , possibly implying an extension of the old province over the islands of the northern and western Aegean as well . Militarily , the Aegean islands came under control of the " Karabisianoi " corps and later of the Cibyrrhaeot Theme during the 7th and 8th centuries . From the late 8th century , however , two separate commands appear in the Aegean : the " droungarios " of the Aegean Sea ( " Aigaion Pelagos " ) , apparently controlling the northern half , and the " droungarios " " of the Twelve Islands " ( " Dodekanesos " ) or " of the Gulf " ( " Kolpos " ) , in charge of the south . The latter command eventually evolved into the theme of Samos , while the former evolved into the theme of the Aegean Sea , encompassing both the islands of the northern Aegean as well as the Dardanelles and the southern coasts of the Propontis . The theme of the Aegean Sea must have been created in 843 : its governing " strategos " does not appear in the " Taktikon Uspensky " of 842 / 843 , which still lists the " droungarios " , but he is elsewhere attested as being active at Lesbos in 843 . The theme of the Aegean Sea was a regular theme , subdivided into " tourma i " and " banda " and with a full complement of military , civil , and fiscal officials . In the areas of the Dardanelles and the Propontis , however , the " droungarios " and later the " strategos " of the Aegean probably shared authority with the Count of the Opsician Theme , to whose jurisdiction these territories properly 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 to man them 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 " ) living 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 subsumed 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 .