CONSTANTINE XI PALAEOLOGOS (1404-1453) , also called Dragases, last Byzantine emperor, was born in 1404 in Mistra, the son of Emperor Manuel II. He was trained as a soldier, and in 1441 conquered the peninsula of Morea in Greece, which had been under the Frankish principality of Achaia, a state established by the Crusaders. Constantine later occupied Boeotia. In 1446, however, the Turkish ruler Murad II reconquered these lands. The Turks had begun their invasions of the Balkans nearly a century before, and now began to close in on Constantinople. Constantine was crowned emperor on Jan. 6, 1449, succeeding his brother, John VIII. A little less than four years later, on Dec. 12, 1452, the union of the Roman Catholic and Greek Orthodox churches was proclaimed in Constantinople in the presence of the papal legate and the Patriarch Gregory. Constantine had been a strong advocate of this union, but the people generally opposed it, and riots ensued. The popular insistence on Byzantine religious autonomy furthered the estrangement between eastern and western Roman Christendom and weakened Byzantine resistance to the Turks. The Turkish sultan, Mehmed II, advanced on Constantinople, sacked the country around it and, after a determined siege, captured the city on May 29, 1453. Constantine was killed in the final assault.