VATATZES GIOVANNI III DUKAS. - Emperor of Nicaea (1222–54). He prepared the fall of the Latin Empire of Constantinople, accomplished under his second successor, Michele VIII Paleologo.
Under him the celebrated union conferences took place at Nicaea and Nymphaeum (near Smyrna) in 1234 between the Greeks, under the patriarch Germanos II, and the delegates of Pope Gregorio IX, namely the Franciscans Aymo and Rofoldo and the Dominicans Ugone and Pietro. Under Innocenzo IV he too continued negotiations for Union. But the motives of this policy of union were not religious, nor did he find among the Byzantine clergy defenders of a religious union with Rome. Because of his charitable works, V. acquired the name of “the Merciful”; indeed, he is venerated as a saint in the Greek Orthodox Church.