1911 Encyclopædia Britannica/John III (Roman emperor)
JOHN III. (1193–1254), surnamed Vatatzes and also Ducas, East Roman emperor, earned for himself such distinction as a soldier that in 1222 he was chosen to succeed his father-in-law Theodore I. Lascaris. He reorganized the remnant of the East Roman empire, and by his administrative skill made it the strongest and richest principality in the Levant. Having secured his eastern frontier by an agreement with the Turks, he set himself to recover the European possessions of his predecessors. While his fleet harassed the Latins in the Aegean Sea and extended his realm to Rhodes, his army, reinforced by Frankish mercenaries, defeated the Latin emperor’s forces in the open field. Though unsuccessful in a siege of Constantinople, which he undertook in concert with the Bulgarians (1235), he obtained supremacy over the despotats of Thessalonica and Epirus. The ultimate recovery of Constantinople by the Rhomaic emperors is chiefly due to his exertions.
See E. Gibbon, The Decline and Fall of the Roman Empire, vi. 431–462 (ed. Bury, 1896); G. Finlay, History of Greece, iii. 196–320 (ed. 1877); A. Meliarakes, Ἱστορία τοῦ Βασιλείου τῆς Νικαίας καὶ τοῦ Δεσποτάτου τῆς Ἠπείρου, pp. 155–421 (1898).