Megas doux

The megas doux (μέγας δούξ; grand duke) was one of the highest positions in the hierarchy of the later Byzantine Empire, denoting the commander-in-chief of the Byzantine navy. It is sometimes also given by the half-Latinizations megaduke or megadux (from Greek μεγαδούξ). The Greek word δούξ is the Hellenized form of the Latin term dux, meaning leader or commander.

History and functions
The office was initially created by Alexios I Komnenos (r. 1081–1118), who reformed the derelict Byzantine navy and amalgamated the remnants of its various provincial squadrons into a unified force under the megas doux. The Emperor's brother-in-law John Doukas is usually considered to have been the first to hold the title, being raised to it in 1092, when he was tasked with suppressing the Turkish emir Tzachas. There is however a document dated to December 1085, where a monk Niketas signs as supervisor of the estates of an unnamed megas doux. The office of "doux of the fleet" (δούξ τοῦ στόλου), with similar responsibilities and hence perhaps a precursor of the office of megas doux, is also mentioned at the time, being given ca. 1086 to Manuel Boutoumites and in 1090 to Constantine Dalassenos.

John Doukas, the first known megas doux, led campaigns on both land and sea and was responsible for the re-establishment of firm Byzantine control over the Aegean and the islands of Crete and Cyprus in the years 1092–1093 and over western Anatolia in 1097. From this time the megas doux was also given overall control of the provinces of Hellas, the Peloponnese and Crete, which chiefly provided the manpower and resources for the fleet. However, since the megas doux was one of the Empire's senior officials, and mostly involved with the central government and various military campaigns, de factο governance of these provinces rested with the local praitōr and the various local leaders. During the 12th century, the post was dominated by the Kontostephanos family; one of its members, the megas doux Andronikos Kontostephanos was one of the most important officers of Emperor Manuel I Komnenos (r. 1143–1180), assisting him in achieving many land and naval victories.

With the virtual disappearance of the Byzantine fleet after the Fourth Crusade, the title was retained as an honorific in the Empire of Nicaea, where Michael VIII Palaiologos (r. 1259–1282) assumed the title when he became regent for John IV Laskaris (r. 1258–1261). It was also used by the Latin Empire: ca. 1207 the Latin emperor awarded the island of Lemnos and the hereditary title of megadux to the Venetian (or possibly of mixed Greek and Venetian descnt) Filocalo Navigajoso ("imperiali privilegio Imperii Megaducha est effectus"). His descendants inherited the title and the rule of Lemnos until evicted by the Byzantines in 1278.

After the recovery of Constantinople in 1261, it reverted to its old function as commander-in-chief of the navy, and remained a high rank for the remainder of the empire, its holder ranking sixth after the emperor, between the prōtovestiarios and the prōtostratōr. As such, it was also sometimes conferred upon foreigners in imperial service, the most notable among these being the Italian Licario, who recovered many Aegean islands for Emperor Michael VIII, and Roger de Flor, head of the Catalan Company. After the mid-14th century, the office was sometimes held together with the office of mesazōn, the chief of the imperial secretariat. In this capacity, Alexios Apokaukos served as one of the leading members of the imperial government during the Civil War of 1341–1347, supporting John V Palaiologos (r. 1341–1391) against John VI Kantakouzenos (r. 1347–1354). The last and perhaps most famous megas doux and mesazōn was Loukas Notaras, who served under Constantine XI Palaiologos (r. 1449–1453) until the Fall of Constantinople.

Cultural references
In the famous 1490 Valencian epic romance Tirant lo Blanc, the valiant knight Tirant the White from Brittany travels to Constantinople and becomes a Byzantine megadux. This story has no basis in actual history, though it may reflect the above-mentioned cases of the office being conferred upon foreigners.