The siege of Bihać () was the besieging and capture of the city of Bihać, Kingdom of Croatia within Habsburg monarchy, by the Ottoman Empire in June 1592. With the arrival of Hasan-paša Predojević as the Beylerbey of the Bosnia Eyalet in 1591, a period of peace established between Emperor Rudolf II and Sultan Murad III ended and the provincial Ottoman armies launched an offensive on Croatia. Bihać, a nearly isolated city on the Una River that repelled an Ottoman attack in 1585, was one of the first targets. Thomas Erdődy, the Ban of Croatia, used available resources and soldiers to protect the border towns, but the Ottomans managed to take several smaller forts in 1591. As the offensive gained pace, the Croatian Parliament passed a law on a general uprising in the country on 5 January 1592.
In early June 1592 Hasan Pasha led his troops towards Bihać, which was defended by around 500 soldiers and commanded by Captain Joseph von Lamberg. The siege lasted from 10 June to 19 June, when Lamberg surrendered the city due to a lack of reinforcements and an insufficient number of defending troops. Lamberg was for this act later tried for treason. Although under the terms of the surrender its citizens were to be allowed to leave or remain in the city without harm, more than 2,000 civilians were killed and 800 were taken captive after Hasan Pasha's troops entered Bihać. The offensive lasted until June 1593 when Hasan Pasha was killed in the Battle of Sisak, which was the cause for the Long Turkish War (1593-1606).
Background
From the 1520s the Ottoman advance into Croatia gained pace. The Croatian nobles elected Ferdinand I of Habsburg at the 1527 election in Cetin as the new monarch, but continuous Ottoman incursions resulted in a significant loss of territory. In 1537 the fall of Klis meant the loss of the last Croatian stronghold in the south of the country. In the 1540s the Ottomans advanced into Slavonia and in the next three decades through western Bosnia in the direction of Zagreb. By the late 16th century Croatia lost two thirds of its pre-war area and more than half of the population. It was reduced to 16,800 km2 of free territory and had around 400,000 inhabitants. The remaining land was referred to as the "remnants of remnants of the once great and renowned Kingdom of Croatia" ().
Numerous ceasefires were signed or renewed between the Ottoman Empire and the Habsburg monarchy, but they were not respected by local Sanjak-beys. Depending on the weather conditions and available military forces they conducted raids without taking into account a truce. Uskoks, irregular soldiers in Croatia, responded with their own raids into Ottoman-held territory. Ottoman authorities settled Vlachs, mainly of Orthodox faith, on the conquered territory and used them as auxiliary units in their wars.
In 1578 Archduke Charles II decided to respond to Ottoman attacks with an offensive to push the frontier back to the Una River. The offensive began in August and the joint Austrian-Croatian troops took back Cazin, Zrin, and Ostrovica, but they were stopped at Bužim and pushed back to the north, losing all gains. Bihać remained basically isolated on the Una River. To strengthen the southern defences the construction of Karlovac as a city-fortress began in 1579. The string of garrisoned forts at the border became known as the Croatian Military Frontier.
The role of Bihać
Following the fall of Knin in 1522 Bihać took the leading role in the Kingdom of Croatia south of the Sava River. It became an important stronghold that protected the area from the Croatian Littoral to the lands around the Una River. From the times of King Matthias Corvinus a garrison was stationed in the city. In 1528 Bihać became a center of a captaincy due to its position near the border with the Ottoman Empire and a relatively large number of residents. There were 25 forts under the command of the Bihać Captain in 1576. However, the number of forts was reduced to only three by 1579: Ripač, Sokol, and Izačić. The rest were either conquered by the Ottomans or were included into the Slunj captaincy. By the 1580s the city was in a dire state. It was almost surrounded by Ottoman territory, villages in its vicinity were abandoned and there were frequent reports of food shortages. Many of its citizens fled the city and there was a large influx of refugees into Bihać from nearby places that were conquered by the Ottomans.