After the crushing loss suffered by the Austro-Hungarian Empire at the battle of Sadowa in 1866, The Empire lost more lands in Italy to the Kingdom of Savoy. The entire Veneto added to earlier losses of Lombardy and smaller duchies in central Italy like Tuscany. Austria’s old defense system centered around the forts of the Quadrilateral. Those forts were all given up after 1866 with the loss of the Veneto and Friulian. A totally new defensive system became needed – enter the Kärtner Sperren.
In the far northeast of Italy, Austrian fortifications were not as elaborate as those in South Tyrol. Here, a modern fort system developed in the early 20th century to both defend and to serve as a potential base for offensive operations against potential Italian aggression – even though, Italy supposedly was an ally to Austria-Hungary.
KARTNER SPERREN
Six forts – the Kärtner Sperren – served to defend the routes leading to Tarasp-Tarvisio on the approach to the Drava Valley – Fort Kluže, Fort Hermann, Paßsperre Predil, Batterie Predilsattel, Seebachthalsperre – on the shore of Lake Raibal – and Fort Hensel in the Canal Valley down from Tarasp. None of the forts of the Kärtner Sperren were of the quality found in the newer Austrian forts in the South Tirol, but like those forts, none of the Kärtner Sperren ever fell to the Italians during World War 1.
FORT KLUŽE
from venice to napoleon
Fort Kluže – Klause in German – was the original defensive position in the upper Isonzo region. A fort was built in the inner gorge of the Koritnica beneath the massive of Rombon to the west. The fort, built by Venetians, defended against possible Turkish incursions from the north – Predil Pass. The fort here, erected in 1491, already became abandoned by the Republic of Venice in 1498. In was not much later in 1509, the Hapsburgs re-occupied the defenses.
Stuck deep in the gorge between Rombon and Swinjak, the fort designed for close-in fighting. The French under Napoleon were able to reduce the fort in 1797 by gaining the heights above on Rombon. Eight years later, they were repulsed.
renewal
The fort was vacant for most of the 19th century until 1881 when it became one of the main defenses for the Kärtner Sperren, Tarvisio – Tarasp and the interior of Austria beyond. The old log fort sitting deep in the Koritnica gorge along the Imperial Road to Gorizia became upgraded to a concrete fort with almost a meter of soil atop to soften the impact of potential shells. Three officers, 120 infantrymen and 56 artillery men manned the fort which literally blocked the road north and south. At the time, the road over Predil Pass was the only way from the south to the north. Vrsic pass was not developed until World War 1.
Designed for in close fighting, there are plenty of loopholes in the fort walls for rifles to stick out. The fort actually – like many of the era – formed a literal roadblock meaning you had to pass through the fort’s walls to go farther. The main problem with the fort, its development in a period of time where artillery made great strides in increasing destructiveness.
In response to the events of 1866, Austria-Hungary built a series of six forts to protect the alpine gateways to the Austrian homeland with Klause being the first of the Kärtner Sperren. Built in a L-shape with the main walls facing south, it was not long before military authorities figured out the fort was already out of date.
updates
Originally, water came supplied from a roof cistern, but that changed later to a pump linked to the river below. Eight machine guns, four 120 mm M-61 cannons and two 90 mm M61 guns made up the fort’s armament though the 120 mm guns updated quickly to M-80 versions of the 120 mm. A reinforced observation dome topped the fort. Enough food stored to enable the fort to withstand a 45-day siege.
To provide more artillery power, the upper fort – Fort Hermann – added in 1900. Kluže was sited in a blind spot regarding Italian artillery. Most Italian heavy artillery sited on the other side of Rombon in Nevea Pass – Sella Nevea – four to five miles away. Those guns were unable to hit the fort deep in the gorge, though they Fort Hermann was another matter. 12 August 1915, Italian artillery scored several near misses, but Kluže never suffered a hit during the war.
GREAT WAR AND BEYOND
By the start of the war, Austrian command had decided to disarm the fort 20 April 1915 and place the guns elsewhere in the area. The fort became a command center for the defense of the Bovec basin. In addition to barbed wire barriers outside of the fort, electric fences also added to the defense though never used. After the Twelfth Isonzo, the fort closed.
Between the world wars, the fort was left intact by Italian authorities – this area became Italian after 1919 until 1945. Fort Hermann above was scavenged for iron, but the same fate was not in store for Kluže. The concrete portal over the Predil road was demolished by the Anglo-American military administration occupying the Bovec region at the end of World War 2.
FORT HERMANN
Fort Hermann developed in 1900 as an upgrade to the older Fort Kluže in the Kortnica gorge below. The walls of Kluže were unable to withstand even a weak bombardment. Hermann, sited 60 meters above, could add artillery defense not only for Kluže, but the guns here – four 120 mm M-96 cannons in armored casements with a range of 6,700 meters and two 105 mm M-80 mortars in revolving armored turrets on the roof with a range of 5,900 meters – could control almost the entire Bovec basin. Two rotating armored observation turrets kept watch on things. A 900 mm searchlight provided light at night.
updates
The new fort served by 13 officers and 227 soldiers. The roof and exposed walls were up to two meters thick built in metal reinforced concrete layers. Granite blocks from South Tirol imported to further give strength to the casements and roof. Water came from a spring far below near the Kortnica River. Electricity from a small hydro-powered generating plant provided lighting and power for ventilation. Connecting Fort Hermann to Kluže below meant a road of almost 1,300 meters carved out of the steep slopes with a 113-meter-long tunnel and one hairpin turn rising 114 meters in elevation. The tunnel needed widening to allow the larger parts of the fort’s equipment to pass through.
The fort was named after Captain Johann Hermann von Hermansdorf. He served as the Austrian commander dying in defense of the fort further up the road at Predil Pass May 1809 against a French incursion. The latest improvements to the fort made in 1909 when three more searchlight caverns became carved from the cliffs 14 meters below the fort along with two machine guns and another artillery observatory. Underground tunnels, telephone and speaking tubes connected the two forts together – the speaking tubes proving more useful for communicating during a bombardment.
WARTIME EXPERIENCE
Even though the fort was only 15 years old by the time of the war, it was already obsolete. But the forts of the Kärtner Sperren did prove to be a deterrent. The Italians never actively attacked the fort even with their initial strength of numbers. Instead, they chose to bombard Hermann with heavy artillery near Nevea Pass over the first months of the war.
Through the summer of 1915 some 3,840 shells rained down on the fort with about 200 hits. Among the shells fired were some weighing 440 and 350 kg shot from 305 mm guns 13 kilometers on the other side of the Canin massif. Their aim helped by an artillery observation post on Krn.
The defenders withdrew from the fort during bombardments. Still nine men died. By May 1916, the fort became abandoned after heavy damage from the hits. The guns found new homes in caves on Svinjak near the artillery base at Čelo.
After the war, landslides made access more difficult with parts of the road washed away. The iron and steel from the fort scavenged in between the wars during the embargo resulting from il Duce’s Ethiopian adventures. I have read where the sentry slits at the tunnel entrance were built by the Italians during their occupation years, though why fortify the road to a destroyed fort?
VISITING TODAY
Only recently has work been done to improve the location to make it safer for visitors. On my first visit here, for example, the tunnel was not lit. The lights are now on inside the tunnel. Explanatory tablets also help make sense of the ruined fort.
Two trails connect into the fort. One basically traversing the lower elevations of Rombon connecting farther on to other trails coming up from Bovec. The other trail heads steeply up the mountain. This was one of the main routes to maintain their presence high on Rombon above. It is a hard path but besides the great views higher up, you also pass sections of old fortifications. The route takes about five hours up and back, though you can also drop back down directly to Bovec passing through the Italian monument on Cukla. It was from down where Mussolini served for some time on the slopes of Rombon during 1916.
FORT PREDIL
Napoleon and the Austrian Empire seemed to be eternally at war. French forces had come up through Fort Kluže in 1797. With another war coming, Captain Johann Hermann von Hermansdorff came to Predil Pass to build a fort guarding the road north from Gorizia.
A two-story blockhouse went up above the road with another smaller building sited closer to the road. A trench connected the two. Construction began in the fall of 1808 with the facility still unfinished the following spring. Too soon, the French were advancing upon Predil. Taking command of the fort and a company of the 62nd Infantry Regiiment Franz Jellachich, Hermann armed and the stocked the fort in preparation for a siege. The men of the 62nd later replaced by Croatians of the 4th Slunj Border Regiment. The unit included four officers and 218 men. Arming the fort were a few cannons.
The French came 16 May. Four regiments of 6,000 to 7,000 men and twelve cannons led by General Jean Mathieu Seras attacked. After two days of fighting, the fort fell. Only one officer and four soldiers of the border guard survived. Captain Hermann fell in the last attack. The French burnt the fort and marched on towards Vienna.
Post Napoleon
In memory of the valiant stand, in 1848, Ferdinand I erected a pyramidal monument with a dying lion stretched out in front. At the same time, the fort was reconstructed as part of the Kärtner Sperren with two parts – lower and upper fort connected by an underground passage. Four cannons were set in the upper fort and there were three positions for cannons in the lower. The fort – Paßsperre Predil – was finished in 1849 and armed with cannons the following year.
It was not long before the interest in the fort waned. A study in 1878 decided a modernization of the Predil Pass fort did not make sense militarily or financially. The new fort at Kluže was built in 1882 in its place. The fort at Predil became used as a warehouse renamed Depot Predil in 1907. The fort remained as a warehouse and a station house for military postal pigeons during World War 1.
BATTERIE PREDILSATTEL
The same commission finding Paßsperre Predil no longer serving a purpose, still found a need to interdict the route from Nevea Pass along Lake Rabelj leading directly north to Tarasp. It was not until 1896 before the War Ministry decided to build a small fort just to the west of the old fort at Predil Pass as part of the Kärtner Sperren to supplement the shorter range guns found at the earlier fort along the north shore of the lake.
Construction began for the new artillery base 300 meters west of Predil Pass 22 June 1897. The fort lies just west of the present border of Italy and Slovenia. The fort finished two years later with cannons installed by 1900. Like many forts designed late in the 19th century, this one was obsolete by the time it was finished. The walls, as constructed, could only withstand shellfire up to 105 mm. Only a small amount of re-barred concrete used, making the walls weaker yet. Worse yet, the battery was in direct line of sight to Italian artillerists at Nevea Pass.
Three 120 mm M-80 cannons armed the fort with two machine guns providing close in defense against infantry attacks. Three 300 mm searchlights illuminated potential nighttime targets. A 1906 update to the fort included an armored observation post. A year later, 50-75 cm of concrete were added to the roof to increase protection.
WARTIME AND BEYOND
In October 1914, the fort, already considered obsolete, was ordered to be disarmed with the guns removed to nearby caves. A first gun removed 26 May 1915 as the Italians began to bombard the battery with 149 mm shells. A respite in the shelling allowed the second gun to relocate in early June. The last cannon removed later in June. By now, the Italians brought up a couple of 305 mm naval guns. These began doing real damage to the structure of the fort.
The Italian bombardment continued until the end of July before they realized the cannons firing from caves above the fort. The caves proved much more difficult to hit than the fort. Try as they might, the Italians were never able to knock out the cannons.
After the Caporetto battle in late October 1917, the fort closed. After World War 2, the site served as border observation post for the Italian army. The fort was thoroughly scavenged for iron and steel bits in the 1930’s. The result is the years have not been kind to the old fort as it remains in bad shape today. Two cannons from World War 2 sit outside the old battery though they have no connection to the fort, itself.
SEEBACHTHALSPERRE
Built between 1885 and 1887, the fort on Raibel Lake built up as one of six planned forts of the Kärtner Sperren closing the path between Italy and the Drava Valley. Seebachthalsperre closed the road over Nevea Pass leading to Tarasp. Construction of the fort fell under the management of Captain Albin Kropsch who previously managed the rebuilding of the larger Fort Hensel in the Canal Valley to the north.
The fort consisted of two sections, a two-storied artillery fort – Werk Raiblersee – and a structure with a gate on the road, itself – Straßensperre. Money constraints limited the guns to 120 mm M-61 cannons, outdated and replaced in 1905 by newer 90 mm M-04 models. A small powerplant allowed the operation of three 300 mm searchlights. Two more machine guns added along with an armored observation dome. The walls of the fort could only withstand shells up to 149 mm which led the fort quickly to obsolescence.
Going into World War 1, the fort was commanded by Captain Schuprina containing infantry troops from the 4th Infantry Regiment and artillerists from the 4th Battalion of the Fortress Artillery. An inspection tour 9 October 1914 determined the fort could not withstand an Italian bombardment and ordered the fort disarmed.
WARTIME AND BEYOND
The six cannons transferred to caves in cliffs above the fort. The first pair moved 15 May 1915 with a second pair on 20 May. One cannon later moved to the lake, and another placed with a third pair of guns on Jerebica – a peak rising above the south side of Raibel Lake. Only an observer and telephonist remained in the main fort. The roadblock station remained fully armed and occupied as it was located out of range of the Italian guns.
The Italians did not realize the fort abandoned and began firing on it 24 May with four 149 mm guns joined the next day by two more 210 mm mortars. Hits were hard to come by because of the location of the fort. Out of 160 shells fired in May, only one hit recorded. There were two hits in June out of 334 shells. In July, 420 mm shells were added to the mix and 31 hits were recorded. Some 25 of the hits were by the heavier shells and the fort was irreparably damaged.
After the ear, the fort along the lake was destroyed by the Italians so not much remains on site today except foundations. The roadblock station can still be visited across the road. Like up at Predil Pass, there are World War 2 guns on the sites, one in front of the roadblock and one on the site of the former fort by the lake.
FORT HENSEL
Like Fort Predil, this fort originally developed in 1808 to block potential French moves up the Canal Valley towards the Drava Valley. The fort designed and constructed under the leadership of Captain Friedrich Hensel was overcome and destroyed by the invading French in 1809. And like at Predil, Captain Hensel and his men died during the battle with the French.
Further, like at Predil, another pyramidal monument lies with a dying lion on the west side of the rock buttress just east of the village of Malborgeth. After the loss of the Veneto following war in 1866, a new fort went up on the site of the old, a part of the Kärtner Sperren.
1 – Werk B; 2 – Communication tunnel; 3 – Tower Werk A; 4 Werk A; 5 – Old road before tunnel.
WARTIME AND BEYOND
Two sections made up the fort, Werk A set above the road with barracks, two howitzer batteries – 100 mm M-80 howitzers – and two-story battery of four guns – two 150 mm M-80 cannons with a later addition of four 90 mm M-4 casement guns. Seven machine guns provided up close defense. Werk B 50 meters below had two towers with an eight-gun – four 120 M-80 in turrets and four in casements – battery in between. The forts featured concrete graded to support hits of up to 210 mm shells.
Set at only two and a half miles from the border, Austrian military authorities realized when war came, the fort would not be able to withstand the newer guns the Italians could bring to bear. Some of the guns removed to outside positions just before the war.
With the war begun 23 May 1915, the Italians began to ready themselves to bombard the fort. Starting 12 June, the fort came under fire for the next 48 days with 300 tons of ammunition dropped on the fort and some 200 hits. Initially, the Italians used 149 mm cannons and 210 mm howitzers, but later 305 mm naval guns joined in. Ten months of further bombardment led to a magazine explosion finally destroying the fort. Fort Hensel closed 19 March 1916, little more than rubble.
You can visit the fort today walking up from the parking lot on the north side of the SS 13 highway. Good boots and long pants for the overgrown vegetation along with a light for any tunnel exploration helps searching through the ruins.