The Krajina in the Balkans is mostly associated with the Military Frontier (Militär Gränze) which acted as the Austrian cordon sanitaire against the Turks in the Middle Ages. The border areas were divided into the following military districts:
Due to the constant border wars, the area became rather depopulated, and the authorities encouraged immigration of various peoples. The majority of settlers were Serbs and Vlachs who came from territories in the southeast, fleeing the Turk occupation. Germans and Magyars mostly came as administrative personnel, and there was a number of other settlers and military persons from other parts of Austria-Hungary such as the Czechs, Slovaks, Ukrainians/Ruthenes and others.During the 1990s, the parts of the Krajina which were found on the territory of the former Yugoslav Republic of Croatia organized into Serb Autonomous Regions and finally the Republic of Serbian Krajina (RSK) in 1991 after Croatia declared independence from Yugoslavia. This political unit lasted until 1995 when Croatian forces in May took its northern areas in western Slavonia Operation Flash, and in August the rest with Operation Storm, displacing most of the Serb population.