From the 1820s to the 1840s, the borderland between the Austrian and Ottoman empires witnessed the creation and development of national movements among Serbs and Croats who lived in administrative and political units with special legal status. One of these territories was the Military Frontier, which turned into a battlefield between the Croatian “Illyrians” (Zagreb) and the Serbian “rodoljubs” (Matica Srpska) for the sympathy of the population. The massive territory and dense population of the Military Frontier attracted the architects of territorial and national integration, and the paramilitary population was considered an instrument in achieving political goals. The population of the Military Frontier spoke the Shtokavian dialect of Serbo-Croatian (which also spread, for example, in Dalmatia and Slavonia), and for this reason the Illyrians took this dialect as the basis for Croatian literary language. In doing so, they were able to spread their ideas through printed materials, which they circulated in the Military Frontier. However, the Serbian “rodoljubs” suspected the Croats of wanting Croatisation and Catholicisation. Both national movements built their agitation on the basis of a historical narrative; Serbs by referring to heroes of Serbian history, and Illyrians by amalgamating Serbian and Croatian heroes together to create a single pantheon for all South Slavs. The Serbian Principality (under the rule of the Ottoman Empire) also claimed their share in the future Serbian unification. For its ruling elite, the Hungarian Srem with the residence of the Serbian Metropolitan was of particular interest. Some Croatian and Serbian politicians worked on a plan of joint action regarding the Military Frontier and turned to Polish émigrés for support.
