Months before the battles on the Isonzo Front started, the Austrian military leaders anticipated that Italy would attack sooner or later. To be prepared, they set up a number of defence lines that would prevent Italians advance across the Slovenian lands deeper into the Habsburg Monarchy. One of these lines, later known as the third line of defence, ran across the Cerkno region. The line started on Mt. Rodica and crossed the Baška grapa valley, the Šentviška planota plateau, continued through the villages of Bukovo, Reka, Šebrelje and further towards Čepovan and the Karst region.
The line of defence was actually a system of trenches, caves, gun positions, road blocks, barbed-wire entanglements and electric wires, etc. The construction of the line started in January of 1915 and was overseen by the head of the Direction for building of fortifications Colonel Alois von Harl who on a couple of occasions visited Šebrelje and Reka for this purpose. Many different military work departments, war prisoners and civilians were involved in the construction.
The villagers of Šebrelje were strictly prohibited from accessing the church of St. John, as a cave and trenches were being built near there. In addition to trenches and entanglements, the defence line also included two supply routes, locally called mule tracks (mulattiere). One of these has recently been cleared and offers a nice walk from the village of Reka to the church. Similar mule tracks criss-crossed the area wherever they were needed. Supposedly, there were also gun positions on some spots in the area of Šebrelje.
The third line of defence was only partly constructed, as many plans never came to fruition. Just before Italy entered the war and the battles on the Isonzo Front started, all labour force was sent to strengthen the defence line along the Soča (Isonzo) River. The third line of defence became less important and only some construction works were continued. All works were stopped at the end of October 1917 with the victory of the Austro-Hungarian and German soldiers over the Italian Army at Kobarid, in Italian literature also known as the Caporetto Retreat.
In the village cemetery at Šebrelje stands a memorial to 46 locals, who lost their lives in World War I. The monument bears the names of people who died on the battlefield, in hospitals, in captivity and of those who were never found. Together with other Slovenian youths and men, the villagers of Šebrelje mostly fought and died on the Eastern Front, where they fought against the Russians, and later on the Isonzo Front and the Tyrolean Front where they fought against the Italians. Only a few men fought on the Balkan Front against the Serbians. Most of them were part of the 27th Home Guard Infantry Regiment (Landwehr Infanterie Regiment Nr. 27), the 27th Reservist Infantry Regiment (Landsturm Infanterie Regiment Nr. 27), 97th Infantry Regiment (Infanterie Regiment Nr. 97), the 7th Riffle Battalion (VII. Feldjägerbataillon), and many other units.
The monument symbolises the death toll that Šebrelje and other parts of the Cerkno region paid in the war. The current number of the lads and men who died amounts to 322.
A steep asphalt road leading to Šebrelje branches off at the Stopnik settlement from the road Idrija–Most na Soči.
It is recommended to park the car in the centre of the village and go on foot for fifteen minutes along the cart track to the church of Sv. Ivan (St. John) at the edge of the plateau, where the starting point is for visits to the remains of WW1 defence positions and the archaeological site of Divje babe.
When coming from the village of Reka, access to the plateau is also possible on foot along a well-groomed footpath (a former mule track).