JOHN OF BRIENNE (c. king of Jerusalem and Latin emperor of Constantinople, was a man sixty years of age before he began to play any considerable part in history. In forty years of tournaments and fights he had won some fame, when in 1208 envoys came from the Holy Land to ask Philip Augustus, king of France, to select a husband for the heiress of the kingdom of Jerusalem, Mary (daughter of Isabella and Con rad of Montferrat). Philip selected John, who assumed the title of king after his marriage. In 1211, of ter some desultory opera tions, he concluded a six years' truce with Malik-el-Adil; in 1212 he lost his wife, who left him a daughter, Isabella; soon after wards he married an Armenian princess. In the fifth crusade (1218-1221) he was a prominent figure. The legate Pelagius, however, claimed the command; and insisting on the advance from Damietta, in spite of John's warnings, he refused to accept the favourable terms of the sultan, as the king advised, until it was too late. After the failure of the crusade, King John came to the West to obtain help for his kingdom. In 1223 he met Honorius III. and the emperor Frederick II. at Ferentino, where, in order that he might be connected more closely with the Holy Land, Frederick was betrothed to John's daughter Isabella, now heiress of the kingdom. John then travelled to France, England and Compostella, where he married a new wife, Berengaria of Castile. After a visit to Germany he returned to Rome (1225).
Frederick II. (who had now married Isabella), now demanded that he should abandon his title and dignity of king, which—so Frederick claimed—had passed to himself along with the heiress of the kingdom. John was now a septuagenarian "king in exile," but he was still vigorous enough to revenge himself on Frederick, by commanding the papal troops which attacked southern Italy during the emperor's absence on the sixth crusade (1228-1229). In John, now eighty years of age, was invited by the barons of the Latin empire of Constantinople to become emperor, on condition that Baldwin of Courtenay should marry his second daughter and succeed him. For nine years he ruled in Constanti nople, and in 1235, with a few troops, he repelled a great siege of the city by Vataces of Nicaea and Azen of Bulgaria. After this last feat of arms, which has perhaps been exaggerated by the Latin chroniclers, who compare him to Hector and the Mac cabees, John died in the habit of a Franciscan friar.
The story of John's career must be sought partly in histories of the kingdom of Jerusalem and of the Latin Empire of the East, partly in monographs. Among these, of which R. Rohricht gives a list (Ge schichte des Konigreichs Jerusalem, p. 699, n. 3), see especially that of E. de Montcarmet, Un chevalier du temps passé (Limoges, 1876 and i881).