The House of Doukas (pl. Doukai; , pl. , feminine form Doukaina; ), Latinized as Ducas (from the Latin title dux "leader", "general", Hellenized as ), was a Byzantine Greek noble family, whose branches provided several notable generals and rulers to the Byzantine Empire in the 9th–11th centuries. A maternally-descended line, the Komnenodoukai, founded the Despotate of Epirus in the 13th century, with another branch ruling over Thessaly.
The continuity of descent amongst the various branches of the original, middle Byzantine family is not clear, and historians generally recognize several distinct groups of Doukai based on their occurrence in the contemporary sources. Polemis, who compiled the only overview work on the bearers of the Doukas name, in view of this lack of genealogical continuity "it would be a mistake to view the groups of people designated by the cognomen of Doukas as forming one large family".
History
Origins
Nothing is known for certain about the family's origin. Later tradition, mentioned by the historian Nikephoros Bryennios, held that they descended from a paternal cousin of the Roman emperor Constantine I who had migrated to Constantinople in the 4th century and allegedly became the city's governor with the title of doux. This tradition is, however, evidently an invention meant to glorify the family, at the time the Empire's ruling dynasty, by 11th-century court chroniclers. In fact, it is more likely that the surname derives from the relatively common military rank of doux. Some authors have raised the possibility of an Armenian descent, but all evidence suggests that the Doukai were native-born Greeks, probably from Paphlagonia in north-central Anatolia, where their estates were located.
Doukai of the early 10th century
The first representative of the family appears in the mid-9th century, during the regency of Empress Theodora (r. 842–855), when he was sent to forcibly convert the Paulicians to Orthodoxy. He is only known as "the son of Doux", although Skylitzes interpolates the name of Andronikos, probably in confusion with Andronikos Doukas (see next). This name is also used by some modern sources--e.g., in the Prosopographie der mittelbyzantinischen Zeit (Andronikos #433).
The first branch of the family to achieve prominence was in the early 10th century (they are usually referred to with the archaic form Doux rather than Doukas in the sources), with Andronikos Doukas and his son Constantine Doukas. Both were senior generals during the reign of Emperor Leo VI the Wise (r. 886–912). In circa 904, Andronikos engaged in an unsuccessful rebellion and was forced to flee to Baghdad where he was killed circa 910. Constantine managed to escape and was restored to high office, becoming Domestic of the Schools. He was killed, however, along with his son Gregory and nephew Michael, in an unsuccessful coup in June 913. These deaths, along with the castration and exile of Constantine's younger son Stephen and the death of a Nicholas Doukas (of uncertain relation to the others) at the Battle of Katasyrtai in 917, mark the end of the first group of Doukai recorded in Byzantine sources. It is likely, as the 12th-century historian Zonaras records, that the Doukai line died out, and that the later bearers of the name were descendants through the female line only.
Lydoi-Doukai under Basil II
Towards the end of the 10th century, there appeared a second family, sometimes known as Lydoi ("the Lydians", likely indicating their origin). Its members were Andronikos Doux Lydos and his sons, Christopher and Bardas, the latter known by the sobriquet Mongos ("hoarse"). It is unclear whether the doux in Andronikos's name is a surname or a military rank; some scholars consider them as belonging to the Doukas clan, although the exact relation, if any, with the earlier Doukai is impossible to ascertain. The family was involved in the 976–979 rebellion of Bardas Skleros against Emperor Basil II (r. 976–1025), but the sons were later pardoned and resumed their careers. Bardas the Mongos is attested as late as 1017, when he led a military expedition against the Khazars.