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).
JOHN IV. (c. 1250-c. 1300), surnamed Lascaris, East Roman emperor, son of Theodore II. His father dying in 1258, Michael Palaeologus conspired shortly after to make himself regent, and in 1261 dethroned and blinded the boy monarch, and imprisoned him in a remote castle, where he died a long time after.
See E. Gibbon, The Decline and Fall of the Roman Empire, vi. 459-466 (ed. Bury, 1896); A. Meliarakes, Ἱστορία τοῦ Βασιλείου τῆς Νικαίας (Athens, 1898), pp. 491-528.
JOHN V. or VI. (1332-1391), surnamed Palaeologus, East Roman emperor, was the son of Andronicus III., whom he succeeded in 1341. At first he shared his sovereignty with his father’s friend John Cantacuzene, and after a quarrel with the latter was practically superseded by him for a number of years (1347-1355). His reign was marked by the gradual dissolution of the imperial power through the rebellion of his son Andronicus and by the encroachments of the Ottomans, to whom in 1381 John acknowledged himself tributary, after a vain attempt to secure the help of the popes by submitting to the supremacy of the Roman Church.
See E. Gibbon, The Decline and Fall of the Roman Empire, vi. 495 seq., vii. 38 seq. (ed. Bury, 1896); E. Pears, The Destruction of the Greek Empire, pp. 70-96 (1903).