John IV

John IV, Byzantine emperor of Nicaea

John IV (John Lascaris) (lăs`kərĭs), b. c.1250, d. after 1273, Byzantine emperor of Nicaea (1258–61), son and successor (under a regency) of Theodore II and last of the Lascarids. Michael Palaeologus (later Michael VIII) overthrew the regency and in 1259 was crowned coemperor. He postponed John's coronation and in 1261 had the boy blinded and imprisoned. It is possible that John escaped from his fortress and went (c.1273) to the court of Charles of Anjou.

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John IV, king of Portugal

John IV, 1604–56, king of Portugal (1640–56). He succeeded as duke of Braganza in 1630. Descended from Manuel I and in illegitimate line from John I, he had the strongest claim to the Portuguese throne when a revolution was planned to cast off the rule of Philip IV of Spain. In 1640 the revolution was successfully carried out, and John became king of independent Portugal. John's policy was to secure foreign alliances, especially with France, in order to consolidate his position against Spain (which did not recognize Portuguese independence until 1668). During his reign the Dutch were expelled (1654) from Brazil, where they had seized territory during the period of Spanish rule. John was unwarlike himself and was devoted to hunting, music, and the arts. The first king of the Braganza line, he was succeeded by his son Alfonso VI. His daughter Catherine married Charles II of England.

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John IV

called the Fortunate. 1604--56, king of Portugal (1640--56). As duke of Braganza he led a revolt against Spanish rule and became king: lost most of Portugal's Asian possessions to the Dutch