Chronology of Catholic Dioceses:Notes on the Dioceses of Sirmium / Syrmia / Srijem, and of Bosna [the Bosnian diocese]

The diocese of Sirmium, first mentioned in the sources in the 4th century, is located in the Slavonian region of Croatia, known as "the breadbasket of Croatia", and in Srijem that is partially located within the territory of the [new] Federal Republic of Yugoslavia.

When Christianity spread from the regions of the upper Drina River to the upper Vrbas River and the rest of the former Pannonia, the Bosnian Diocese was established for that territory. The earliest reference to the diocese is from 1088. In approximately the year 1250, the bishop and his cathedral chapter moved to Djakovo, probably due to a clash with the members of "Bosnian Church" - Patarenes or Bogomils. In 1683, when Turks were defeated in the Battle of Vienna, Slavonia and most of Srijem were liberated from Turkish rule and the Church administration was reorganized. In 1773, Pope Clement XIV merged the Bosnian and Srijem Dioceses into a Bosnian-Srijem Diocese with the see in Djakovo.

The territory of the Srijem Diocese had been the ancient Syrmia Diocese during early Christian times and was overrun by the Huns and the Avars. In 885, following the death of St. Methodius, it was extinguished. In 1231, the diocese was restored and in 1773 merged with the Dakovo (Djakovo) Diocese. Since 1963, it has been known as the Dakovo (Djakovo) and Srijem Diocese and is a suffragan of the Zagreb Metropolitan See.

-CT (from Dr. Alberto Mioni)