Bands of Uskoks fought a guerrilla war against the Ottomans, and they formed small units and rowed swift boats.

An extremely curious picture of contemporary manners is presented by the Venetian agents, whose reports on this war resemble a knightly chronicle of the Middle Ages.

The Ottoman conquest of Bosnia and Herzegovina during the early years of the 16th century drove large numbers of ethnic Croats from their homes, which in the town of Klis prompted the formation of the Uskok military.

[6] Large numbers of fugitives from Herzegovina, Dalmatia, and Bosnia fleeing the Ottomans, joined the ranks of the Uskok bands.

Owing to its location, Klis Fortress was an important defensive position which stands on the route by which the Ottomans could penetrate the mountain barrier separating the coastal lowlands from around Split in Croatia, from Ottoman-held Bosnia.

Christian guerilla resistance in Ottoman-occupied areas of Dalmatia and Bosnia caused these people to flee and settle down, first at the fortress of Klis along the Military Frontier, then at Senj.

[10] A body of these "uskoks" led by Croatian captain Petar Kružić used the base at Klis both to hold the Turks at bay, and to engage in marauding and piracy against coastal shipping.

[6] Although nominally accepting the sovereignty of the Habsburg Emperor Ferdinand I,[Note 1] who obtained the Croatian crown in 1527, Kružić and his freebooting Uskoks were a law unto themselves.

[6] After Petar Kružić's death, and the lack of water supply, the defenders of Klis finally surrendered to the Ottomans in exchange for their freedom.

[13] At Senj, the Klis Uskoks were soon joined by other refugees from Novi Vinodolski in northwestern Croatia, from Otočac on the Gacka River, and from other Croatian towns and villages.[when?

So, the uskoks fitted out a fleet of swift boats, which were light enough to navigate the smallest creeks and inlets of the shores of Illyria.

[17] Throughout the following years the Habsburgs were at arms with the Turks, giving the Uskoks the opportunity to repeatedly raid Bosnia and Dalmatia.

[18] By 1573 the Uskoks caused considerable concern in Venice with frequent attacks once Venetian attempts of protection had proven to be ineffective.

From 1577 onwards, Venice endeavored to crush the pirates without offending Austria, enlisting Albanians in place of their Dalmatian crews, who feared reprisals at home.

Led by Telli Hasan Pasha, the beylerbey of Bosnia, the Ottomans managed to capture a number of uskok settlements, killing and enslaving the population.

Austria was involved in war with the Ottomans and the Venetian admiral Giovanni Bembo blockaded Trieste and Rijeka (Fiume), where the pirates forwarded their booty for sale.

A raid by the Uskoks upon Istria resulted in an agreement between Venice and Austria, and Count Joseph of Rabatta was appointed to act as commissioner to those in Senj as well as the chief negotiator with the Venetians.

[21] In response to this offense the Uskok captured a galley of Venetians, slaughtered the crew, and used the blood of the victims to flavor their bread.

The pirates and their families were, accordingly, transported to the interior, where they gave their name to the "Uskoken Gebirge", a group of mountains on the borders of Carniola now called Žumberak.

Their presence has also been traced near Učka in Istria, where such significant family names as Novlian (from Novi Vinodolski), Ottocian (from Otočac) and Clissan (from Klis, older orthography), were noted by Italian historian Carlo de Franceschi in 1879.

Other important aspects of the Uskok heroic honor were loyalty to their city, army, and band; honorable attention to every knight and obligation; readiness to lay down their lives or spill their blood in time of war; experience in warfare; ability to benefit their city; success and glory in duels with the Turks and other enemies of the Christian faith; and severity in punishing those who were disobedient or rebellious.

[30] It was also made known the Uskok qualities that would cancel out one's honor: reluctance to shed one's own blood; failure to engage the enemy in battle; groundless boasting; avoidance of risks on the frontier; failure to take prisoners, trophies, or booty; meanness in rewards to comrades or spies; the absence of any general recognition of one's manliness; and the lack of battle scars or wounds.