The town of Kozara has a marginal role in the history of the medieval Bosnian state, considering that it is a town that was under the rule of the Bosnian kings for a relatively short time, so its medieval history is primarily related to the territory of the Kingdom of Hungary. The town was located in the county of Sana, which was first mentioned in written sources in 1200 in the charter of the Hungarian king Emerik, where it is stated that the Vodice possession, which was gifted to Prince Stjepan on that occasion, borders the districts of Sana and Dubica (districtus Zaue et Dubicha). What particularly attracts attention, when it comes to historical sources from the 13th century related to the county of Sana, are Ragusans’ reports on the slave trade from this very area, which could point to the existence of religious teachings that the Catholic Church did not approve of. The famous Croatian family of the Dukes of Blagaj, later also known as of Vodice, ruled the possessions in the county of Sana, but also in the territory of the neighboring counties of Vrbanja and Dubica. Sana county fell under the jurisdiction of the Bishop of Zagreb, which is evident from the list of Catholic parishes of the Zagreb Diocese from 1334. Due to previous research, we are fairly familiar with the county’s borders, so it is safe to assume that in the west it extended to the rivers Una and Japra, in the east it extended to the mountains Kozara and Piskavica, while in the north-south direction it stretched from Kozara to Mrin. The seat of Sana county was originally probably the place of the same name, and later it became the town of Kozara.
The oldest preserved mention of the town of Kozara is from 1334, when it was mentioned as the center of the county in Sana district and as the location of the church of St. Martin (ecclesia sancti Martini de Cozara). According to the document issued in Kozara on February 10, 1360, it is a free town and the seat of the county of Sana. Namely, on that occasion, Latko, sub-prefect (pod-župan) and sub-castellan of Sana, convened the assembly of the county of Sana in the free town of Kozara (ad liberam villam Kazara). Five years later, on December 18, 1365, the sons of a certain Golub sold their property there, in front of the Sana župan (prefect) Bokuč and the judges. The mentioned župan (prefect) Bokuč was also the castellan of the fortress of Kozara, as well as of the nearby Greben (castellanus castrorum Kozara et Greben) which was handed over to the Hungarian king in 1357 by Grgur and Vladislav Pavlović and Grgur Stipanić and thus committed treason against the Bosnian ban Tvrtko. The town of Kozara was last mentioned under Hungarian rule in 1385, when the Slavonian bans Stjepan and Ivan Banfi made promises to Duke Vuk Vukčić, brother of the Great Duke Hrvoje Vukčić Hrvatinić, that they would stand up for him with their queen after the latter occupied the town of Greben.
Taking advantage of the difficult circumstances in Hungary, which occurred after the death of King Louis I, the Hrvatinići, with the aim of territorial expansion, undertook military activities towards Hungarian possessions in their neighborhood. During these military activities in 1389, Grand Duke Hrvoje Vukčić Hrvatinić also captured Kozara. In this way, the town of Kozara entered the territory of the Bosnian state and became part of the territorial and political entity known as Donji Kraji, which was ruled by Hrvoje Vukčić Hrvatinić in this period. In the famous Gospel of the tepčija Batalo, from 1393, it is written that this famous Bosnian nobleman came into possession of the county of Sana. Tepčija Batalo Šantić, a member of the feudal family of Šantić, owned the county of Lašva and the town of Toričan, and after marrying Resa, the daughter of Duke Vukac Hrvatinić and sister of Hrvoje Vukčić, the county of Sana and probably the town of Kozara came under his control. In 1396, the župan (prefect) of Sana was Vukac, who, on the orders of Grand Duke Hrvoje, issued a charter to two Ragusan merchants in the town of Kozara guaranteeing them safety in his county. Also, in a charter of Duke Hrvoje in 1412, Gašpar Dijanišević is mentioned as a witness from the county of Sana.
In the first years of the 15th century, Prince Hrvoje Vukčić Hrvatinić was at the peak of his power and as such was instrumental in creating the internal and external circumstances in Bosnia. However, already in 1413, this Bosnian nobleman found himself in the disfavor of the Hungarian king Sigismund, due to an attack on the possessions of Sandalj Hranić Kosača, who was then preoccupied with the war against the Ottomans, and soon a systematic attack on his possessions began. In the attack of 1413, the county of Sana was lost, along with the town of Kozara. Kozara was handed over to King Sigismund by Hrvoje’s relative Vuk, the son of Miloš Družić from Guča Gora in Lašva, which certainly paid off for him because in 1425 he was generously rewarded with the king’s charter. According to this charter of King Sigismund, Kozara was then in his possession and would remain so for the remainder of the period, indicating that the town was lost to the medieval Bosnian state in 1413. However, the southernmost part of the county of Sana will remain under Bosnian control, where the new county of Sana was formed. In the charter issued by King Stjepan Tomaš to the sons of Ivaniš Dragišić, dated August 22, 1446, certain parts of this county are also mentioned.
It is noteworthy that Kozara distinguished itself in its defense against the Ottoman invasion. In a charter from 1473, Nikola Sekelj is credited with successfully defending the town of Kozara from Ottoman attacks for ten years. Despite their courage, the defenders of the town were forced to surrender to the Ottoman conquerors in 1518. As a result of this act, Kozara, albeit in a different manner, re-entered Bosnian territory and remains in this situation to this day. The town has, however, undergone a change in name in historical sources and is now referred to as Kozarac. Today, this name refers to the area under the Kozara fortress in Prijedor.
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