ILLYRICUM, ILLYRIA

ILLYRICUM, ILLYRIA. This is the old Roman name for a province that included modern Yugoslavia and Albania (qq.v.). Historically, Illyricum was early under the jurisdiction of the papacy (q.v.). But after the invasion of the Slavs in the 6th c. and 7th c. and the missionary work of SS. Constantine-Cyril and Methodius in the 9th c., the region’s southern half fell under the effective rule of the Ecumenical Patriarch (q.v.). This confirmed what earlier imperial legislation under Leo III had sought to do by law (732/3). The shift in jurisdictional authority occasioned considerable tension between Rome and Constantinople (qq.v.) throughout the 9th c. (See Photius.)