THE POSAVINA BORDER REGION OF CROATIA AND BOSNIA-HERZEGOVINA: DEVELOPMENT UP TO 1918 (with special reference to changes in ethnic composition) Ivan CRKVEN^I] Zagreb UDK: 94(497.5-3 Posavina)''15/19'':323.1 Izvorni znanstveni rad Primljeno: 9. 9. 2003. After dealing with the natural features and social importance of the Posavina region in the past, presented is the importance of this region as a unique Croatian ethnic territory during the Mid- dle Ages. With the appearance of the Ottomans and especially at the beginning of the 16th century, great ethnic changes oc- cured, primarily due to the expulsion of Croats and arrival of new ethnic groups, mostly Orthodox Vlachs and later Muslims and ethnic Serbs. With the withdrawal of the Ottomans from the Pannonian basin to the areas south of the Sava River and the Danube, the Sava becomes the dividing line creating in its border areas two socially and politically different environments: the Slavonian Military Frontier on the Slavonian side and the Otto- man military-frontier system of kapitanates on the Bosnian side. Both systems had a special influence on the change of ethnic composition in this region. With the withdrawal of the Ottomans further towards the southeast of Europe and the Austrian occu- pation of Bosnia and Herzegovina the Sava River remains the border along which, especially on the Bosnian side, further changes of ethnic structure occured. Ivan Crkven~i}, Ilo~ka 34, 10000 Zagreb, Croatia. E-mail:
[email protected] INTRODUCTION The research subject in this work is the border region Posavi- na between the Republic of Croatia and the Republic Bosnia- 293 -Herzegovina.