JOHN IV, pope. — Of a Dalmatian family, son of a scholasticus, he succeeded the elderly Pope Severinus in 640 while relations between Rome and the East were very tense due to the usual theological disputes; he proved uncompromising in matters of faith, succeeding in obtaining from Emperor Heraclius a letter of justification regarding the *Ecthesis*; after Heraclius' death, conciliatory factions gained the upper hand at the court of Constantinople, while J. IV continued energetically to defend the orthodox doctrinal position; he died on 12 Oct. 642 and was buried in St. Peter's. He brought to Rome relics of martyrs from Dalmatia and took an interest in the ransom of Istrians and Dalmatians who had fallen into slavery during Slavic raids.
Bibl.: F. Gregorovius, Storia della città di Roma nel medioevo, I, Rome 1900, pp. 441 sqq.; A. Crivellucci, Storia delle relazioni tra lo Stato e la Chiesa, III, Pisa 1909, p. 29; Fliche-Martin-Frutaz, V, p. 463 and passim; O. Bertolini, Roma di fronte a Bisanzio ed ai Longobardi, Bologna 1941, pp. 325-27, 705. Paolo Brezzi