Bust of Çaka Bey in the Istanbul Naval Museum..
Tzachas was originally a raider, who was taken as a prisoner by the Byzantine Empire during the reign of Nikephoros III Botaneiates (ruled 1078–81). Tzachas entered Byzantine service and advanced rapidly through imperial favour, receiving the title of protonobilissimus and rich gifts. However, when Alexios I Komnenos (r. 1081–1118) deposed Botaneiates in 1081, Tzachas lost his position and fled Byzantium.
From ca. 1088 on, he used his base at Smyrna to wage war against the Byzantines. Employing Christian craftsmen, he built a fleet, with which he captured Phocaea and the eastern Aegean islands of Lesbos (except for the fortress of Methymna, Samos, Chios and Rhodes. A Byzantine fleet under Niketas Kastamonites was sent against him, but Tzachas defeated it in battle. In 1090/91, however, the Byzantines under Constantine Dalassenos recovered Chios.
Undeterred, Tzachas rebuilt his forces, and resumed his attacks, even proclaiming himself emperor (basileus) and seeking to conclude an alliance against Alexios I with the Pechenegs in Thrace. In 1092, Dalassenos and the new megas doux, John Doukas, were sent against Tzachas, and attacked the fortress of Mytilene on Lesbos. Tzachas resisted for three months, but finally had to negotiate a surrender of the fortress. During his return to Smyrna, Dalassenos attacked the Turkish fleet, which was almost destroyed.
In spring 1093, Tzachas attacked the port of Abydos in the Sea of Marmara. Alexios I called upon the Sultan of the Seljuk Sultanate of Rum Kilij Arslan I (r. 1092–1107) to attack Tzachas from the rear. The Sultan advanced to Abydos, where, at the pretext of inviting Tzachas to a banquet, and had him murdered. However, in ca. 1097 a "Tzachas"—possibly the original Tzachas' son—is reported as still holding Smyrna when the Byzantine army under John Doukas recaptured the city.
- The Turkish form of "Tzachas" does not appear in any historical documents. The name "Çaka" or "Çaka Bey" prevailed especially in modern Turkey, after Akdes Nimet Kurat used it in his work Çaka: Orta Zamanda İzmir ve Yakınındaki Adaların Türk Hakimi, Istanbul, 1936. (Turkish), ... yüksek siyasî ve askerî görüş sahibi olarak büyük önem taşıyan bu bey'in adının gerçek söylenişi henüz tamamen kesinliğe kavuşmuş değildir. Bu hususta şimdiye kadar üç ihtimal ileri sürülmüştür: Çaka, Çağa, Çakan. AN Kurat'ın bunu «Çaka» kabûl ederek eserini de «Çaka Bey» diye adlandırması, özellikle memleketimizde Çaka şeklinin yaygınlaşmasına yol açmıştır denebilir. (Tarih Dergisi, Cilt 20, İstanbul Üniversitesi Edebiyat Fakültesi, İbrahim Horoz Basımevi, 1983, p. 56. (Turkish))
- Brand, Charles M. (1991). "Tzachas". In Kazhdan, Alexander. The Oxford Dictionary of Byzantium. Oxford and New York: Oxford University Press. p. 2134. ISBN 978-0-19-504652-6.
- Dawes, Elizabeth A., ed. (1928). The Alexiad. London, England: Routledge & Kegan Paul.