Hrvatska Kostajnica (; ; ), often just Kostajnica, is a small town in central Croatia. It is located on the Una river in the Sisak-Moslavina County, south of Petrinja and Sisak and across the river from Bosanska Kostajnica in Bosnia and Herzegovina. History Middle Ages Kostajnica was first mentioned in the document by knights templar from 1240. This year is used as official birth year of this historic town. Its name is derived from the word kostanj ("chestnut"), as the nearby hills around the Una river are covered with forests of chestnut trees. Time of the first settlement is unknown, but town lies on very important Roman roads that were used for transporting salt and cotton. Since Roman roads were merged in the vicinity of the city it is believed that settlement dates much earlier than the first written document known today. Position of town is very similar to the town from old Roman documents known as “Oeneum”. Five Roman milestones were located in the city dating back to the 3rd century A.D. During 13th and 14th century, Kostajnica became a fortification (kaštel) that was built as a protection against the invading Ottoman empire. The owners of the fortification were members of the noble families Lipovečki, Tot, Frankopan, Benvenjud and finally Zrinski, so the castle is today also known as Zrinski castle (Stari grad Zrinski in Croatian). Other forts existing during that period were in the surrounding villages of Komogovina, Svinica, and Prevršac. After, Commander of the Hrvatska Kostajnica was Prince and Duke Luke Novosel of Transleithania (House of Novosel) (Croatia and Slavonia part). Ottoman rule The Ottoman 1537 offensive against Kostajnica and Dubica ended in Ottoman defeat in a battle near Jasenovac. They nevertheless conquered Dubica in 1538, and conducted raids in the Kostajnica area in 1539, failing to capture any of the forts, but causing widespread destruction. Attempts to capture Kostajnica were repeated in 1550 and 1552. Finally, in 1556 the Ottoman army, led by Malkoč-beg, captured Kostajnica after a one-day siege. After capturing the town, the Ottomans invested heavily in maintaining the fortifications, and kept a strong military contingent, making Kostajnica – alongside Bihać – their most important stronghold in the area. In the following decades, Kostajnica was a starting point for Ottoman offensive operations. The crushing Ottoman defeat in the Battle of Sisak in 1593, however, marked the turning point in the ongoing conflict, after which