Constantine Dalassenos ( thalassokrator ) Constantine Dalassenos ( , " fl . " ca . 1086 – 1093 ) was a prominent Byzantine military leader on land and sea during the early reign of Emperor Alexios I Komnenos ( r . 1081 – 1118 ) , especially in the campaigns against Tzachas of Smyrna . His life is only known from the " Alexiad " of Anna Komnene . Biography . According to the " Alexiad " , Constantine Dalassenos was related to Alexios I through his mother , Anna Dalassene , although the exact connection is unknown . He first appears in 1086 / 1087 , when he was sent as an envoy to receive Sinope and the surrounding towns from a Turkish " chiaus " who had turned renegade , had become baptized and collaborated with the Byzantines . Dalassenos became Sinope ' s governor , while the " chiaus " was made " doux " of Anchialus . In spring 1090 , Dalassenos was raised to the post of " " doux " of the fleet " and given command of the Byzantine naval forces against the emir Tzachas of Smyrna . Tzachas , formerly a Byzantine vassal , had built a fleet of his own , had seized several Aegean islands , and raided others . After taking Lesbos ( except for the fortress of Methymna ) and Chios , he defeated a Byzantine fleet under Niketas Kastamonites . Taking advantage of Tzachas ' s absence in Smyrna , Dalassenos disembarked his troops on Chios and immediately assailed the island ' s fortified capital . Although the Byzantines seized the town ' s harbour , they failed to break through into the city itself . Meanwhile , Tzachas had gathered 8 , 000 men , according to the " Alexiad " , and set off to the island ' s relief . His army marched on land up to the shore opposite the island , while his fleet followed , sailing along the shore . Dalassenos had charged Constantine Opos with hindering the Turks from crossing over , but when the Turks did so under the cover of night , the latter refused to engage them when he saw that Tzachas had had his ships chained together . The two armies engaged in skirmishes , but soon negotiations began . Dalassenos deferred any decision ; and when Tzachas returned to Smyrna , perhaps to gather more forces , he gathered his men , prepared more siege engines and took the citadel of Chios in a surprise attack . In 1091 , Dalassenos is recorded as participating in Alexios I ' s campaign against the Cumans in the Balkans . In the decisive Battle of Levounion on 29 April 1091 , he commanded the army ' s left wing . In 1092 , he was again sent against Tzachas , with the title of " thalassokrator " ( Greek : θαλασσοκράτωρ , " master of the sea " ) , subordinated to the new " megas doux " , John Doukas . The two commanders were to attack Mytilene on Lesbos , still held by Tzachas . Doukas , at the head of the land forces , arrived first , and attacked the town . The siege lasted for three months , before Tzachas offered to surrender the town in exchange for safe passage back to Smyrna . Doukas agreed , but Dalassenos , who had just arrived , attacked the Turkish fleet . He captured many of the Turkish vessels , and ordered the crews , including the rowers , executed . Dalassenos then returned to Constantinople . In spring 1093 , when Tzachas attacked the port of Abydos in the Sea of Marmara , Alexios again dispatched him against the emir by sea . At the same time , however , Alexios called upon the Sultan of the Seljuk Sultanate of Rum Kilij Arslan I ( r . 1092 – 1107 ) to attack Tzachas from the rear . The Sultan complied , and in an audience had Tzachas murdered . Nothing further is known of Dalassenos after this .