Relief of the battle of Sisak.
Map of Croatia in 1593.
Although fairly autonomous, Croatia was part of the Hungarian kingdom and thus political relations between Croatia and the Ottoman Empire were mainly confined to interactions with local authorities, such as correspondence about and negotiations of borderland issues.
Despite the fact that formal political relations were limited, the Ottoman Empire was nevertheless an important presence for the peoples of Croatia, especially after the early 15th century when the continued expansion of the Muslim Ottomans began to be perceived as a threat to the Catholic population of northwestern Croatia and central Bosnia. After the fall of Bosnia to the Ottomans in 1463, Ottoman expansion continued in the southern areas (Herzegovina and the coastland up to the river Cetina), yet in other places it could not break the defense system set up by King Matthias Corvinus of Hungary (r. 1458-90). A new wave of Ottoman conquests began in 1521 and lasted until 1552, at the end of which the Ottomans had conquered a good portion of present-day Croatia, including territories between the rivers Drava and Sava. For approximately the next 150 years, due mainly to the fact that the Habsburgs had established an efficient defense system in Hungary and Croatia, the borders in the north and south stabilized. The border was, in effect, a strip of no-man’s-land running between Koprivnica and Virovitica near the river Drava to Sisak, then westward to a point near the present-day town Karlovac, then southward to the Plitvice lakes, and in the southwest to the Adriatic; in Dalmatia the Venetian- held territory was reduced to small enclaves around the principal towns.
However, east of the Habsburg border in the central region of Croatia, between the rivers Una and Kupa, Bosnian ghazis or Muslim warriors were still making gains against Croatian nobles, who were fighting without Habsburg support. The situation changed in 1593 when the Croatians broke the offensive power of the Bosnian troops with lasting consequences in a battle at Sisak, on the confluence of the rivers Sava and Kupa. In 1606, at the Ottoman-Habsburg Treaty of Zsitvatorok that ended the war of 1593-1601 between the two empires, the Croatians made some further territorial gains, but from 1699 to 1718 Croatia’s surface almost doubled as a result of the treaties of Karlowitz and Passarowitz that ended the Long War of 1684-99 between the Ottomans and Habsburgs. However, it took some time to negotiate clear lines of control and actual change came slowly. The jurisdiction of the Croatian autonomous administration in the northern parts of the reconquered lands down to the river Danube was extended in 1745, while the rest was integrated in 1871 and 1881, after the Habsburg Military Border was abolished.
The rout at Mohacs was a momentous event for the Croats. The joint kingdom established in 1102 was ended. The Croats were without a ruler. A few days after Ferdinand’s coronation in Pressburg the Sabor assembled at Cetingrad, near Bihak, to elect him as king of Croatia. Most Croats backed the Habsburg candidate, although they were determined to make use of the choice to reaffirm Croatia’s privileges and its status as a kingdom.
On New Year’s Day 1527 the Sabor met at the Church of the Visitation of St Mary in the Monastery of the Transfiguration under the presidency of the Bishop of Knin and the heads of the Zrinski and Frankopan families.
Following final negotiations with three Habsburg plenipotentiaries, they elected Ferdinand as king of Croatia. The Sabor made it clear to Ferdinand that they had elected him in the hope of gaining more military aid against the Ottomans – `taking into account the many favours, the support and comfort which, among the many Christian rulers, only his devoted royal majesty graciously bestowed upon us, and the kingdom of Croatia, defending us from the savage Turks…’. The ceremony closed with a Te Deum and `a tumultuous ringing of bell’. The document of allegiance was sealed with the red-and-white coat of arms of Croatia, which marks the first known occasion on which the chequer board symbol was used as Croatia’s emblem.
The Sabor of Slavonia, which was dominated by Hungarian magnates, did not share the Croats’ enthusiasm for the Habsburgs. In 15 05 it had pledged never to accept another foreign (non-Hungarian) prince, and supported Zapolya.
Krsto Franltopan, the brother of Bernardin, emerged as a powerful supporter of Zapolya in Slavonia and joined him in flirting with the Turks, although he was killed in the early days of the civil war, Simon Erdody, the Bishop of Zagreb, was another pillar of the pro-Zapolya faction, laying siege to his own diocesan capital in 1529 and burning the outlying hamlets. A force loyal to Ferdinand raised the siege of Zagreb, destroyed the Kaptol, and extinguished this threat to the Habsburg claim. In 1533 a joint session of the Sabors of Slavonia and Croatia-Dalmatia confirmed Ferdinand’s title to all the Croat lands.
Croat hopes of recovering large tracts of the country with the aid of the Habsburgs were disappointed. As an election sweetener, before the assembly in Cetingrad, Ferdinand promised to pay for 1,000 cavalry and 1,200 infantry to defend the Croatian border, while the Estates of Inner Austria, Carinthia, Carniola and Styria voted money to supply garrisons in the frontline cities of Bihać, Senj, Krupa and Jajce in Bosnia. But this investment was insufficient to keep the Ottomans at bay. The Habsburgs pockets were not deep enough, and the complicated arrangement of their possessions, in which there were many estates with overlapping jurisdictions, made it difficult to harness their resources. Instead, there were stopgap measures and half-built castles, manned by soldiers who often were not paid for years on end.
The results on the ground were depressing. From 1527 to the 1590s the Croats continued to lose territory. In 1527 the Ottomans overran Udbina, in Lika. In the same year the last Christian-held fortress in central Bosnia, at Jajce, also collapsed. By the end of the 1530s, the Turks had mopped up the last spots of resistance on the southern bank of the River Sava in northern Bosnia, and had advanced through Slavonia as far west as Naŝice and Poriega. In Dalmatia, the Turks conquered most of the land that was not occupied already by Venice. Obrovac fell in 1527 and in 1537 the fortress of His, the last Croat stronghold south of the Velebit Mountains succumbed. In the 1540s the pace of the Ottomans’ advance in Slavonia was equally relentless, as they pushed westwards as far as the line between Virovitica, Cazmanad Sisak.
During the next three decades they continued their advance through the north-west of Bosnia in the direction of the Habsburg garrison town of Karlovac, south-west of Zagred. The biggest disaster of the period was the loss of the royal free city of Bihać in 1592. The town was razed and the inhabitants – those not killed – fled. The loss of Bihać to Croatia was permanent. The city was rebuilt and revived as a Muslim city surrounded by Serb orthodox peasants. The fall of Bihać was almost followed by the loss of Sisak, which was attacked in 1593 by an Ottoman force under Hasan Predojević, the Pasha of Bosnia. Had Sisak crumbled, the way would have been open to Zagreb. The threat threw the Sabor into panic and a hastily recruited force of about 5,000 professional soldiers under the Ban, Thomas Erdody, was despatched to the town. The Ottomans were too confident. The Croats, made fearless by terror of the consequences of failure, took the initiative and fell on the Turks with ferocity. This rare and surprising victory was not followed up. An attempt to recapture neighbouring Petrinja, where the Ottomans had erected a fortress, was not successful. Nevertheless, the Ottomans had reached their high-water mark in Croatia by the end of the 1590s, leaving a strip of territory around Zagreb, Karlovac and Varaždin under the control of the Sabor and the Habsburgs.
The Habsburgs called the string of garrisoned castles they maintained in Croatia the Military Frontier – Vojna Krajina in Croatian. It was not a piece of territory but simply a series of forts manned by German mercenaries who were backed up by local troops. At first, most of these local soldiers were Croat refugees who had fled north from Dalmatia or trekked out of the interior of Bosnia, ahead of the Ottoman advance. The soldiers manning these garrisoned forts became known as frontiersmen – granićari in Croatian.