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YAHYA OF ANTIOCH. Christian Arab historian of the 11th century who lived in Egypt under the Fatamids. He authored a continuation of the History by Eutychos of Alexandria covering the years 938–1034. His work concentrates on Egypt and on Syria, about which there is much useful information on the military campaigns of Nikephoros II Phokas and John I Tzimiskes, as well as the persecution of the Caliph al-Hakim in 1009.

YARMUK, BATTLE OF. See EMESA; GHASSANIDS; HERAKLEIOS; KHALID; SYRIA; UMAR.

YASSI ADA SHIPWRECK. The underwater excavation of a Byzantine merchant ship near the island of Yassi Ada, Turkey. The excavation was directed by George Bass during the summers of 1961 through 1964, sponsored by the University Museum of the University of Pennsylvania.

The ship, which was constructed during the first quarter of the seventh century, had a cypress keel about 12 meters long. It crashed into a reef and sank in 625 or 626, based on the latest of the 70-odd coins found in the wreck. Its cargo was between 850 and 900 wine amphoras, weighing some 37 tons. Additionally numerous items used by the ship’s crew, including anchors, lamps, weighing implements, mattocks, hammers, gouges, files (and other carpentry tools, useful for repairs), fishing gear, knives, and kitchen utensils (e.g., a bronze cauldron and frying pan) were found.

Most important is what was revealed about the ship’s construction, something not known through Byzantine literary texts, but only through such excavations. The traditional Greco-Roman practice of building up the hull planking was used, beginning at the keel, one strip at a time, shaping each plank with adzes. Each plank was closely fit to the adjoining ones and fastened with mortise-and-tenon joints. Above the waterline, however, internal ribbing was used, and the planks fastened with iron nails. Further savings of labor and money was achieved by using rough half-timbers for wales and ceiling of the hull.

Thus, the Yassi Ada shipwreck revealed a remarkable transition in the history of ancient construction: from solely plank-first construction fastened with mortise-and-tenon joints to the use of frame-first construction onto which the planks are simply nailed. See also AEGEAN SEA; MEDITERRANEAN SEA; NAVIGATION; POTTERY; TRADE AND COMMERCE; TRANSPORTATON.

YAZDGIRD III. See SASSANIANS.

YAZID II. Caliph of the Umayyads from 720 and 724, remembered for his edict of 721 that ordered the destruction of all images, which he viewed as a form of idolatry. Despite the fact that this decree was issued several years before a similar one by Leo III, there is no evidence that Yazid II’s decree inspired Leo III’s Iconoclasm. See also ICON; UMAYYAD CALIPHATE.

YOLANDE. See LATIN EMPIRE.