The Seljuk campaigns in the Aegean refer to the ground and naval actions conducted by the Seljuk Turks, chiefly under the leadership of Tzachas of Smyrna against the Byzantine Empire. A fierce opponent, Tzachas constructed the first Turkish navy and captured a few Aegean islands, supplemented by the conquest of Smyrna and Abydos. In the aftermath of the First Crusade Alexios I launched a counter-attack which regained the territories lost.