Klis Fortress in Croatia


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Mar 8, 2013
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Klis Fortress in Croatia – History and War (wordpress.com)

History of Klis

Historical development of Klis was guided primarily by its geographic position. Fortress, raised on an almost inaccessible cliff situated between mountain ranges of Kozjak and Mosor, always had a major military significance. The fortress controlled the primary line of communication between the interior and the coast of central Dalmatia. Its strategic and historical significance make it one of most important fortification monuments in Croatia.

History of Klis starts in 2nd century BC. During this period, an Illyrian tribe of Delmats (Delmatae, Dalmatae) lived in the area, and it is likely that an Illyrian hillfort or at least a settlement already existed at the location of the fortress. But first reliable news about the fortress are brought only in 10th century, by the Roman (Byzantine) Emperor Constantine Porphyrogenetos. He writes of an event when Avars and Slavs captured by guille the Roman fortress of Kleisa located on the cliff, and thus enabled the conquest of city of Salona in the first half of 7th century.

Arrival of Croats was an important event in history of the fortress, as two centuries later, Klis became one of capital cities of Croatia. In a copy of a document from 852., Klis is mentioned as a property and a court (ex curte nostra que Clissa dicitur) of duke Trpimir and his predecessor Mislav, and soon became a seat of old Croatian Coastal county.

After 11th century, Klis comes under control of Kings of Hungary and Croatia, and is often governed by their viceroys. In early March of 1242., Klis was unsuccessfully beseiged by Tatars (Mongols) under belief that king Bela IV had taken the refuge there. In late 13th century Klis came into possession of the powerful Šubić family, which kept it in their possession for over 50 years. During this period, Klis has its own notary, stamp, and a court of law. From 1355., Klis is again under royal protection and enjoys a long period of peace.

From late 14th to late 15th centuries, Klis is a focus of struggle between Croatian nobles and Hungarian-Croatian kings for control of the city. But the most devastating period of history of Klis begins in early 16th century, when it forms part of border defences of Kingdom of Croatia against the Ottomans. Important role in this struggle was played by Petar Kružić, captain and duke of Klis, who for two decades had repelled the Ottoman attacks while also defending Klis from Venice. But Petar Kružić was killed in combat against Ottomans at coast of Solin, and thus Klis was forced to surrender.

Petar Kružić approaches Klis fortress

Petar Kružić on a way to Klis

This meant the loss of the strongest Croatian fortress in Dalmatia, and river Jadro became a border between Venetian Split and Ottoman Klis. This situation lasted until April 1596., when a hundred-odd Croats, led by Split nobles Ivan Alberti and Nikola Cindro, managed to take the fortress by surprise. They soon received reinforcements from Uskoks, Republic of Poljica, Kaštela, Brač, and others. But Ottomans quickly organized, and it was not long before the fortress and its 1500 defenders were besieged by 8 000 Ottoman troops. Commander of Croatian Border, general Jural Lenković, attempted to relieve the fortress, but was defeated by the Ottoman army which at that point numbered 10 000. Both Ivan Alberti and Nikola Cindro died in this battle as well. Fortress had to surrender on 31st of May. It should be noted that there was a possibility to save the fortress, but Venetians preferred to see Ottomans have the fortress rather than Croats, and so prevented the Papal, Neapolitan and Croatian reinforcements from assisting the fortress.

Klis thus remained unquestionably Ottoman for the next 50 years. But during the Candian War, in March 1648., ten thousand Venetian soldiers led by general Leonard Foscolo, assisted by large numbers of local population, besieged Klis which was at the time defended by thousand Turkish soldiers. After ten days of fighting, during which various defensive positions changed hands multiple times, Turks surrendered, leaving Klis on 31st of March.

With conquest of Klis, Venetians had achieved their greatest success in the Candian War. The area of Klis was set up as a separate military administrative district, with seat in Klis. Klis remained under Venetian rule until 1797., when it was transferred to Austria. Between 1805. and 1813. it is under French rule, and from 1813. to 1918. it is again under Austria. Then, from 1918. to 1990., it is a part of Yugoslavia, and from 1990. part of independent Croatia.

Architectural Evolution of the Fortress of Klis
Klis was not built according to a plan, but rather developed spontaneously. Having likely inherited the location of a prehistoric settlement or fort, it gradually developed and evolved during a time period stretching from antiquity to 19th century. During this time, Klis had served as a fortress of Roman Empire, Croatia, Hungary, Ottoman Empire, Venice and finally Austria.

The oldest fortification must have taken up the highest area of the cliff, gradually encroaching onto the lower-lying areas. Between wartime destruction and later modifications, traces of the original Illyrian hillfort and Roman castrum had almost completely disappeared. Development of early Croatian period is likewise almost completely unknown, as is that through the Middle Ages, as fortifications changed often during this period. During his tenure as a commander, Captain Petar Kružić managed the fortress’ maintenance, collecting for this purpose donations from local populace and foreigners alike. On his behest, popes Leon X, Clement VII and Paul III sent help in food, weapons and money, much of which was used to fortify the fortress.

Despite damage from frequent sieges, much of it from Ottoman cannons, at the time of the loss Klis was not significantly damaged. During the Ottoman rule, fortress saw only regular maintenance and minor repairs, and thus mostly kept its original medieval structure.

Only Venetian rule will result in significant modifications, primarily to first and third defensive walls. As a result, Klis today is a complex architectural structure within which are dominant elements of Venetian defensive architecture of 17th and 18th centuries. Venetian renovation of the fortress began immediately after its capture, under supervision of generals Leonard Foscolo and Ferdinand Scot, while the project of renovation itself was crafted by engineers Alessandro Maglio, Giono di Namuru and Vincenzo Benaglio. Ten years later, renovation was entrusted to engineer Giuseppo Santini, who likely carried it out based on the original Maglio’s project.

During their first two decades of rule over Klis, Venetians had carried out the most extensive project of renovation and reconstruction the fortress had ever seen. Klis thus lost its medieval appearance, with tall towers being demolished and replaced with low-lying bastions. General layout of the fortress remained the same, with division into three circuits of walls. Old water cisterns were repaired and additional ones built. Also built were storage rooms for weapons, ammunition and other equipment, as well as quarters for fortress’ complement which numbered 300 soldiers and officers, and an apartment for governor (provedadore).

Plan of Klis with parts denoted (in Croatian)

Klis as it looks today

Despite this, the terrain prevented extensive modifications which resulted in the fortress retaining most of its medieval structural elements which were a major disadvantage in the new gunpowder era. In 1746., one of last Venetian renovations of the fortress was carried out, with modifications to the eastern areas of the first defensive wall and some repairs to others. After cessation of Ottoman danger to Dalmatia, Venetian interest for maintaing the fortress gradually evaporated, with Klis consequently being in a rather ruined state when Austrians took it over. Fortress only saw extensive repairs and some minor modifications during second Austrian rule.

Defensive Fortifications
Shape and extent of the fortress is primarily determined by the terrain it is situated on. Fortress is built on a steep cliff, with fortress achieving highest point at 385 meters above sea level. Fortress itself is of an irregular polygonal shape, with length of 304 meters (east-west) and width of 53 meters (north-south). Outer circumference of the fortress is 725 meters, with the wall following the line of the earlier medieval fortification. Fortress is a multiple or a complex fortress which achieved gradual articulation and expansion through addition of new lines of walls around its core. Total surface area is 8842 square meters, which was well used as about a third of that area is taken up by structures.

Due to being conditioned by the shape of the cliff, contours of the fortress are irregular. Walls themselves are thin, with maximum thickness of no more than two to three meters. Walls themselves are built with rubble core while external surfaces are built of the cut stone. Walls are up to nine meters tall at fort’s northern side, and cliff itself falls down steeply further 40 or so meters.

As with other fortresses and cities throughout history, fortifications of Klis had developed as a result of multiple factors. Its geographical location had, in the Middle Ages, provided it with very favourable geostrategic conditions. This, combined with masterful construction and utilization of terrain, allowed a small number of defenders to resist a much more numerous enemy. Over time, with addition of new walled circuits, fortress also gained on defense in depth, significantly improving its defensive power. Most important were defensive positions on the northern and western sides, which were most frequently assaulted. Thus, these areas were strongly fortified, first with tall towers and then with powerful bastions. Defensive conception was predominantly vertical, first passive and then – with development of firearms – active.

First Defensive Wall
Outermost defensive wall is located at the far western area of the fortress. It defends the area of the first gate, which is located slightly northwards of the location of the medieval entrance to the fortress that were destroyed in the Venetian siege of 1648. To protect this part of the fortress, Venetians then fortified it with bastions. They raised bastion Foscolo to the east of bastion Avanzato, but had to demolish it in 1657 along with other fortifications. The entire area remained unfortified for the next ten years, after which it received temporary wooden fortifications, and finally stone fortifications in two belts. Older belt, Avanzato, is enclosed by the fortifications of the entrance.

Main entrance currently present in the fortress was built by Austrians in 1820s after they had removed old Venetian Porta del Primo Recinto. Shaped in neoclassicist style, it is crowned with a terrace at the top. As with other entrances, it used to have double gates whose interspace could be filled with earth to protect it from cannon fire.

Main entrance to Klis fortress, constructed during Austrian rule

Main Entrance
Entrance fortifications flank the entrance from the northwestern side, having been raised by Venetians in the first half of 18th century.

Position Avanzato is first mentioned as a forward position (Posto Avansato) in 1688., with the purpose of protecting the first and the second entrances which, due to their size and increased usage of gunpowder artillery, presented major weak points in fortress’ defense. In 18th century, Venetians built position Tantaglia (“pliers”) to its north. Within the ground level of its wall there is a narrow passage (“Caponera”) or a casamat (“Casamatta”) with a small door leading to the platform of the entrance fortification, and a row of loopholes. Above it are parapets with two gunports.

Second Defensive Wall
Second defensive wall encompasses the central portion of the fortress, between the first and the third wall, from whom it is separated with additional walls.

Second entrance (Porta del Secondo Recinto) is fortified, with a terrace on top, and is approached by a slope. Entrance replaced the old medieval entrance that was heavily damaged in the siege of 1648. Small defensive anteroom had also existed there until 19th century when it was removed. Modern look the entrance received in 1820s, when it was repaired and reshaped in neoclassical style. The entrance is flanked from the northwest by a wall and round Oprah tower, which defended the entrance in the case of attack.

Entrance to the second circuit

Medieval Oprah tower was once the most important defensive position of the western part of the fortress. It is first mentioned in a letter of duke Pavao III Šubić as Oprack, while during Ottoman rule it was called Pasha’s tower. In 17th century, Venetians gave it a name Torretta, which was also used by Austrians. However, Croatian name Oprah was used the whole time. The tower displays several building phases: from medieval which had shaped its escarp from foundations to the platfrom, to baroque which had shaped its preserved northern part of the crenellation with its two cannon ports. Insides of the tower are filled with rubble and earth, providing it with greater resillience against siege engines and cannons. Originally much taller, it was damaged in the siege of 1648., and received new, lower crenellation during rebuilds.

Oprah tower and the eastern position Scala are connected by a cortina towards Megdan (Cortina verso il Meidan). Cortina has numerous embrasures, while a guard track follows its southern side, serving also as a defensive position. Cortina kept its medieval crenellated design all the way to mid-17th century.

Position Scala is relatively small, with irregular square ground plan. It has thin walls, which originally had four embrasures, which were later replaced by two cannon ports. Named after the staircase located at its southern side, it defended the Cortina and the path which passes along the northern side, leading towards the main entrance.

Artillery barracks were built by Austrians in 19th century, replacing the old guard house. Originally it had two floors, but the top floor was destroyed in 1931., leaving only the ground floor. Building is set up against the raised terrain of cortina, while southern face contains entrance and symmetrically set windows.

Ahead of the artillery barracks stretch the preserved walls of flanking fortifications, shaped in irregular rectangle. Larger elongated position was called Mezzo, “the middle one”. During Venetian period this was also the location of the of the guardhouse and a fortified entrance towards the eastern and southern parts of the fortress.

Second circuit was also the location of two of water cisterns. These were crucial, as Klis had no natural water wells to enable it to outlast frequent and long sieges it was subjected to. Out of seven water cisterns, two largest ones were located here, next to the staircase leading to the third entrance. Small stairs to the west of cisterns lead to square terrace which was the location of military quarters until 1938., when they burnt down.

Southern part of the walled area is accessed by a sharp incline, located on the lowest part of the plateau encircled by a cortina above the town. This area was likely built in the late Middle Ages, with the purpose of protecting the fortress from the southern side. None of the objects which had existed in this area – small quarters, hospital and gunpowder storage – had been preserved until today, having been demolished by Austrians during renovation of the fortress in 19th century. Eastern part of the cortina contains two walled-off secondary entrances which would allow the unnoticed entrance and exit from the fortress. On the western side of the southernmost part of this wall, Venetians had in 17th century built a new entrance – New Doors (Porta Nuova, Porta della Sortita). These were walled off in the second half of 18th century, while the Madonna position was expanded in its western part during 1820s.

Third Defensive Wall
Third defensive wall is located at the raised part of the cliff. It is thus the fortress’ most important element – its citadel. Raised above other defensive positions, it represented dominant position of the fortress, its center and the final defensive line. This area was likely the location of the original Illyrian hill-fort, and then Roman castrum which served as a core for the later Croatian fortress.

Third entrance is approached via a wide paved staircase which leads to the entrance, itself constructed as a passage though a guardhouse with a small defensive area in front (Barriera). It was reconstructed by Venetians in mid-18th century, when they also added two gunports. In 1753., top floor was vaulted, and on it constructed a terrace with addition of cannon ports and embrasures. Upper floor is accessed by external staircase, and it contains a single room with two cannon ports.

Main entrance to the third defensive wall

Main entrance to the third defensive wall

Flanking tower (Torre Bastionata) is located at the southeastern side of the entrance. Tower is of irregular shape, owing to complex construction in multiple phases. Founded in mid-18th century, and finished in 1763., its purpose was defense of this circuit and part of Varoš. Tower is entered from the north, and it has multiple cannon ports in the walls. Its ground-level room is now filled with earth and rubble, while its top has a terrace with a parapet, with cannon ports and embrasures.

The armory contains one of oldest water cisterns, of irregular square shape, with semicircular roof. Across it is a ruinous weapons storage, which to Venice served to store tools and to Austria for cannon mount storage. At eastern side, there was a smaller weapons storage which was removed in the 19th century. Sheltered by a cliff, there is also an 18th century gunpowder storage. In 1830s, Austrians, in the ground in front of the southern facade of the storage, made a small water cistern.

Small quarters are located on the upper part of the walled area. In the beginning they were quarters of the armory master, then as quarters for soldiers and officers, and finally as a toast/rusk storage. It originates most likely from 17th century.

Duke’s quarters or Providur’s Flat is located at an rocky elevation northwards of the armory. They may have been raised at the foundations of the oldest buildings of Croatian rulers and then dukes of Klis, known as Duke’s house. It originally consisted of a ground level and a floor above, with providure’s office being located near the entrance. Ground level also contained storage and rooms for officers, soldiers of the watch, and serwants. Upper floor had rooms for officers, living room, room for servants, kitchen and the pantry. After Austrians repaired it in 19th century, Duke’s Quarters served as offices for fortress command staff and the engineering unit.

Bembo bastion is located at the far western end of this wall, where previously stood Kružić’s Tower as well as positions Speranza and Elsa. It is the largest artillery position in the fortress, of irregular rectangular shape. Northern side is protected by tall, partly ruined parapet with wide cannon ports, while parapets of the western and southern wall are reduced to the level of the platform. To the East, it connects to the central pentagonal bastion Malipiero, itself bordered by tall parapets with narrow cannon ports. Below it is a vaulted passageway leading to the position Maggiore.

Position Maggiore is the second largest position in the fortress. It is likewise protected by tall parapets with cannon ports. In its northwestern corner is located the new gunpowder storage, built by Austrians in 1820s, after they had removed Venetian quarters which had housed first officers, then infantrymen, and finally chancellors and fortress serjeants. Position itself has a floor plan in the shape of irregular rectangle, with a small accompanying annex in front of the entrance on the southern side, while walls up to three meters thick carry a round-arched vault constructed from brick and topped by a gable roof.

Position Šperun (Speron – Sperone, Spiron) is the most exposed part of this enwallment, as well as the fort itself. It is a narrow protruding prow, which once controlled Ozrna height as well as the road passing along the eastward side of the cliff. This was the location of the tall Duke’s Tower, which however had been heavily damaged during liberation of Klis in 1648. and demolished. Of once-tall parapets of this position, only low parapets with a row of loopholes remain.

Church of St. Vid is located between Bembo and Malipiero bastions, and is the most beautiful object of the fortress. This former Ottoman mosque had been built on the place of the old church, and is one of few examples of islamic architecture in Dalmatia. It was built soon after fall of Klis in 1537., as endowment of its conqueror, Murat-beg Tardić. After Venetian conquest it was turned into a church. Building itself is of square floor plan, and has an eight-sided roof likely built during Venetian rule. Today’s floor, made of stone blocks, is much taller than the original Ottoman floor.

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