Uskok War The Uskok War , also known as War of Gradisca , was fought between the Austrian and Spanish on one side and the Venetians , Dutch and English on the other . It is named for the Croatian soldiers known as " Uskoks " used by the Austrians for guerrilla warfare . Since the Uskoks were checked on land and were rarely paid their annual subsidy , they resorted to acts of piracy . Uskoks did not limit their attacks to Turkish vessels but also Venetian merchantmen were often attacked by the Uskoks ( and later also attacked by Spanish corsairs ) . The Venetians tried to protect their shipping with escorts , watchtowers , and other protective measures , but the costs became too high : 120 , 000 Thaler s annually in the 1590s , 200 , 000 in the 17th century , and 360 , 000 by 1615 . In December 1615 , Venetian troops laid siege to Gradisca , located on the Isonzo River . Venetian - Habsburg tension increased and escalated into the Uskok War ( 1615 – 1618 ) . The conflict was provoked by the activities of the Uskok pirates , stationed by the Habsburg rulers along their frontiers as part of their military border system . The pirates raided Venetian ships from harbours on the eastern Adriatic coast , within the domain of Ferdinand , Archuduke of Styria and future Holy Roman Emperor . Ferdinand was unwilling to stop their attacks , but instead used the Uskoks to exert pressure on Venice in an attempt to hinder the republic ' s ambitions in northeastern Italy . Ferdinand was aided by Spain , while Venice attracted Protestant assistance from , among others , the Dutch Republic . After the Uskok War , the bond between Venice and the United Provinces was finally formalized in an alliance . Ambassador Francois van Aerssen visited Venice in 1620 to ratify a treaty , signed the year before in The Hague , which entailed mutual assistance if one of the two republics were to enter into war with the Habsburg powers . Venetian relations with the Habsburgs grew less strained during the second half of the seventeenth century . The Venetians launched a major diplomatic campaign for allies , since the Uskoks were vassals of then - Archduke Ferdinand of Inner Austria , who was likely to seek help from the Holy Roman Emperor Matthias ( his uncle ) and King Philip III of Spain ( his brother - in - law ) . In September 1616 , Count John Ernest of Nassau - Siegen agreed to raise 3 , 000 men in the Dutch Republic for Venetian service . They arrived the next May , followed six months later by another 2 , 000 with a contingent of English volunteers . Support from the Spanish was prevented on sea by a flotilla of 12 Dutch and 10 English warships , and on land by the war in Mantua . First military events . The first military events started in January 1616 in Collio , where a garrison of Uskok and Segani was in favour of the Austrian faction . After the faction of Veneto gained an advantage in Mariano and after they placed the cavalry , they moved forward to Gradisca on 24 February 1616 and they encamped in Farra . The Venetian Republic , being powerful at sea , was the absolute master of the Adriatic , while Austria had only a small part of the coast of Trieste and Croatia , which was blocked by the Republic of Venice . Any vessel could pass this border without paying taxes and without holding a Venetian residence . In January 1616 in Collio , which was guarded by a Uskok and Segnana in Vipulzano and San Martino of Quisco . The Venetian troops left a detachment in the field of Mariano , and arranged the chivalry in Romans and Medea , who camped near Farra and were advancing on 24 February 1616 towards Gradisca . The siege lasted twenty - nine days . The Venetian fleet crashed in Trieste , whose garrison was reinforced by Captain Sebastian Zuech . The castle of San Servolo , the Karst Edge , had sacked two of Venetians infantry insignia are intercepted at the Rio Ospo from 240 German musketeers that causes them among a dozen killed and wounded . The administrator Benedict Lezze with 1 , 000 cavalry and infantry occupied the Venetian castle of San Servolo . Uscocchi and Croatian troops led by Wolfang Frangipane , Count of Tersato vicegeneral of Croatia , commandant of a military expedition came to Monfalcone on 26 November 1615 and plunder its territory . The Venetian garrison that was restricted to shoot some guns from the fortress . On the Carso , Slovenia , and between Corgnale in today in today ' s Piedimonte , gathered 1 , 200 Croatian soldiers , 500 horsemen and 500 Uskoks , fronted by 3000 the Venetians led by Benedict Lezze administrator . The Duke of Savoy in Venice offered an alliance but the Senate refused . Carry out the raids and fires on the Karst of Trieste and Istria . The administrator of today Palmanova mobilize militias Savorgnan and Friuli and has 3 , 000 men with whom stood on the Isonzo and the raids began around the fortress of the Habsburg Gradisca . In the first phase of the war , action in Venice ( troops left Palma ) was characterized by the use of offensive forces , their mobility and surprise . The Archduke actively renounced to defend a number of cities ( Cervignano , Aquileia , Castelporpetto , Maranutto , Mariano , Romans d ' Isonzo , Cormons , Medea Sagrado ) , castles and villages - some of them surrendered to Venice to be attacked before - to stand stronger and more defensible positions . At this retreat , we must note , however , the offensive in Istria , where the Austrians broke easily going up to Pola , Duecastelli and Sanvincenti . Since rejected , the Uskoks plundered and destroyed the surrounding villages . The Venetian Loredan administrator then asked , and received , substantial reinforcements to defend the South from the incursions of Uskoks Istria . Parenzo e Rovigno sent the artillery , and weapons in Pola Valley and Duecastelli food and weapons . The militias were concentrated in Barbano ( Istria ) and Sanvincenti . Battle of Zaule . Provveditore Benedetto da Lezze with a galley and a few smaller ships landed in the valley of Muggia . Venetians , with 6 squads guided by captain Fabio Gallo , occupies the saltpans Zaule and begins to destroy them . From the plateau karst intervenes Captain Daniel Francol , followed by the count of Trsat and the musketeers under Captain Sebastian Zuech . Venetians , caught by surprise , fled to the ships . The administrator Lezze cuts the saline bridges behind him , blocking the escape of his troops . The Venetian galleys opened fire with cannons , hitting both enemies and friends . Venetians lost some man , killed in action , some drowned and they lost also a flag . The Austrians had 10 casualties , including the voivoda Verdonoviz , leader of the Croats , who was killed by a cannon shot from a galley . First Siege of Gradisca . In 1616 the Venetians started defensive works for the siege in Farra and Gradisca . The archducal disturbed them with the chivalry from Gorizia and Lucinico . With three major culverins , four guns and three children culverins and other pieces on the side of Farra , damaging the walls and the buildings ; and silenced the enemy artillery , except colubrina " Cerberus " from the castle . The assaults on the breaches were repulsed with heavy losses . The Venetians launched another futile assault in which only the courses differed . Giustiniani lifted the siege and retreated to Mariano . In September , Johan Ernst van Nassau - Siegen agreed to raise 3 , 000 men from the Dutch Republic for Venetian service . They arrived the next May , followed six months later by another 2 , 000 with a contingent of English volunteers . Support from the Spanish was prevented on sea by a flotilla of 12 Dutch and 10 English warships , and on land by the war in Mantua . Ferdinand only had 4 , 000 soldiers to defend Gradisca , but received military , political and financial support from the Spanish as part of a larger deal : Philip agreed to give aid against the Venetians and support Ferdinand as the next Holy Roman Emperor in return for the cession of Alsace , Finale Ligure and Piombino . This led to a negotiated settlement between Ferdinand on the Venetians in which many Uskok ' s pirates were executed or exiled , and a permanent Austrian garrison was installed in Senj . Battle of Lucenico . Pompeo Giustiniani was flanked by Francesco Ferrante and Martinengo de Rossi . Marcantonio of Manzano , the squadrons of cavalry Camillo Trevor and a group of Albanians resumed raids on the neck , killing 60 fighters and citizens of the castle of St . Florian and the surrounding area . Adam von Trautmannsdorf , received reinforcements , passed the Isonzo and strengthened Lucenico and Gradisca . The Venetians attacked Trautmannsdorf at dawn on three columns from Mariano , Corona , San Lorenzo and Mossa , led by Orazio Baglioni . Albanians left in the middle of the mercenaries Ferrante de Fulvio Rossi and Count of Porcia , the cavalry on the right of Francis Camillo Martinengo and Trevor , for a total of 4 , 000 men . The Albanians occupied the trenches on Lucinico but instead of advancing they plundered the dead soldiers , while the other columns were welcomed by a large fire , suffering heavy losses and were forced to retreat . The Venetians reduced military activities while the Austrians received reinforcements . War in the Alpine Range . The superintendent Barbarigo was replaced by Antonio Priuli on the 2nd of June and obtained fresh Friulian and Dalmatian troops , strengthens the field fortifications and conducts diversionary raids in Istria , attracting opposing forces . The Austrians responded with other raids in Monfalcone . In Monfalconese armies face each extending the entrenchments . Choices and Albanian troops ran a strong Venetian attack Stella , on the heights in front of Fogliano , so named for its hexagonal shape , but are rejected by serious losses . The war extends over the mountains . The Venetians plunder the territories of Kobarid and Tolmin , Schmit , an English mercenary captain with 400 men , hired by the bishop of Bamberg , with as many regular Austrian took Pontebba on August the 8th . A counterattack led by Marcantonio of Manzano retook Pontebba e Malborghetto on August the 13th . Pontefract dealing with a sleight of hand , ed by militias and resume Pontebba Malborghetto , obtained by the cavalry led by James Antonini that plunders the surroundings of Tarvisio . The Venetians then fold up to Pontefract and strengthen defenses . Camillo Tevigiano with numerous Stradioti Cividale make a foray into the valley to Kobarid and Tolmin Soca . The Austrians , affected by the disease , lose a third of the militian , then retire on the left bank of the Isonzo . The Venetians occupied Lucenico , abandoned by their opponents . Even the last outposts repass the Austrian Isonzo infiltrating at night between the Venetian locations . Pompeo Giustiniani puts 4 guns and 2 culverin against Fort San Pietro ( on Mount Fortin ) and the bombardment began , prompting the captain Sibel to give the yield . The defense comes out with the honors of war . Second Siege of Gradisca . In Monfalcone landed the Count John Ernest of Nassau with 4 , 000 Dutch mercenaries , bringing the Venetian effectives to 20 , 000 men . There arrived also some British volunteers . The Venetians were preparing for a massive advance on 1 June : Giovanni de Medici , and his head quarter moved to Monfalcone ; Govanni Martinego from Mariano through Cassegliano reached San Pier d ' Isonzo , the right wing of the cavalry led by Ferdinand Scotus from Mariano through Fratta and Monfalcone , reached Vermegliano , where he was0 joined by the infantry of Orazio Baglioni , the Dutch mercenaries advancing towards the heights of the Carso , the brothers Francis and Charles Strassoldo with 200 armor , 300 arquebusiers , two squadrons of horse and one of infantry took place between Farra and Mainizza and , joined by two large companies of horses , one from Cividale and one from Udine . At dawn on 2 June the Dutch occupied San Martino del Carso . The Austrians abandoned all positions between Gradisca and the heights , which were occupied by the Venetians . Camillo Trevigliano with a thousand men committed the Austrians in Gorizia . Six galleys bombed the castle of Duino . The following day on 3 June the Dutch overran forte delle Donne ( on Monte San Michele ) and after the arrival of artillery of Martinego they opened a gap . Afterwards , the 42 defenders surrendered . Two days after also the 400 men of the Fort Imperial surrendered to the Dutch in exchange for their free passage . The Venetians erected a few small reduits , placing forty pieces , and were prepared to launch the final assault to the park of Rubbia where the Austrians had their headquarters . Captains and civil began to evacuate the city of Gorizia , but on 6 June Henry of Nassau , refused to continue the assault because of the fatigue of his men . The Austrians revived and strengthened their defenses , but during an inspection on 7 June , Trautmansdorf was killed by a shot of artillery . He was succeeded by the Spanish Baltasar Marradas who made false matches to capture the Venetians , saying them that Gradisca was well equipped . The Austrians rejected an assault on the park of Rubbia on 9 June , tried again and again rejected on 12 June with Henry of Nassau , which is among the wounded , meanwhile , was able to bring food in Gradisca . There were also rejected the third slaught on 20 June and the attempt of winding through Merna , because of the resistance to the passage of the captain Melgruber Vipava . on 22 June . The Venetians refrained from further offensive and intensified the blockade of Gradisca . The diseases reduced losses and their effects , the Dutch were halved . Austrian reinforcements arrived , led by Albrecht von Wallenstein . The Austrians advanced in three columns from Farra , Gradisca , and Gorizia and assaulted the camp of the Albanian militias of Camillo Treviglio , inflicting them heavy losses , including the commanders Marcantonio Manzano , Leonardo and Pietro Avogadro Gualdo . An Austrian column attacked the Venetians that blocked Fort Stella killing Orazio Baglioni . The Austrians also took over the trenches on Monte San Michele . Lando was saved with difficulty . Giovanni de Medici left the command for health reasons , replaced by Prince Luigi d ' Este . During the night the Venetians raised other forces and batteries around Fort Stella , but Albrecht von Wallenstein managed to bring reinforcements and supplies to fort Stella . The aids already arrived in Gradisca , that was still besieged . Don Giovanni , in order to block the enemies ' supplies coming from the " Vallone " ( a valley ) , wanted to occupy Sdraussina and Fogliano ( south of Gradisca ) , to cut the Austrian communications . The occupation of these villages , was planned in detail by Giovanni de ' Medici on 25 August 1617 , but was not carried on since it was reputed dangerous . So , the Austrians managed to bring relief to fort Stella from the Karst . Ferdinand only had 4 , 000 soldiers to defend Gradisca , but received military , political and financial support from Spain as part of a larger deal : Philip agreed to give aid against the Venetians and support Ferdinand as the next Holy Roman Emperor in return for the cession of Alsace , Finale Ligure and Piombino . This led to a negotiated settlement between Ferdinand and the Venetians in which many Uskok pirates were executed or exiled , and a permanent Austrian garrison was installed in Senj . Aftermath . Archival study of Istrian circumstances at the time of this warfares documents and supports a thesis that in the clash between Austrians and Venetians " a squadron ( banderijska ) , and not an ethnic , consciousness was dominant ; this was not sort of progressive struggle against foreign rule but an unfortunate manipulation of our people by foreign camps , " which subordinated the local warriors " to the interests of foreign powers and pushed the Croatians ( and to a lesser extents Slovenes and Italians ) into a brutal brother - killing - brother war " . Bertosa goes on to say that in the warfare of 1615 - 1287 : 30 - 50 percent of Istria ' s inhabitants were killed or hauled off as captives , 90 - 99 percent of the livestock was destroyed , 60 - 90 percent of the houses were burned and destroyed , and 90 - 98 percent of the land was abandoned . Peace . At the front there was fighting but both sides yearned for peace . Ferdinand , already in anticipation of problems in Germany , wanted to break away from the commitment of the war with Venice . Venice although has not really been fully engaged in the conflict because of fear and of direct intervention by the Spanish - did not think the conflict would contribute to his cause . The truce was signed on November 6 and the armies began to demobilize on 28 , but the prolongation of the peace talks and their uncertain outcome suggested that the Netherlands were recruiting new contingents of soldiers would arrive in Venice . In the " Treaty of Peace concluded through the mediation of Philip III of Emperor Matthias de ' Romans and King of Bohemia and Archduke Ferdinand of Austria and the Republic of Venice " ( now known as the Preliminary Treaty of Paris and the Treaty of Madrid ) is resolved that the pirates are driven from the maritime areas belonging to the House of Austria . The Venetians , returned to their Imperial and Royal Majesty all the places occupied by them in Istria and Friuli . The Venetians , however , emerged from the conflict head - on , getting what they wanted , namely the expulsion of Uscocchi by Mark and at the same time , the recognition of sovereignty over the Gulf , but the overall picture was bleak and the press indicate that during the first seventeenth century Friuli was in misery , famine , fever , livestock diseases and incursions of wolves .