The question of the defence of Sofia
In 1879, when the country was liberated from the Turks, Sofia was defended by some redoubts (tabja) :
<![if !supportLists]>1. <![endif]>the fortification north-east of the church of Santa Sofia, on the terrace above the district of Kjuljutzit,
<![if !supportLists]>2. <![endif]>the Slatinskja lunette near the War School,
<![if !supportLists]>3. <![endif]>the Aiva-dede redoubt at the ecclesiastical seminary,
<![if !supportLists]>4. <![endif]>the tabja Evrejska at the Macedonia brewery, raised in 1854 during the Crimean War,
<![if !supportLists]>5. <![endif]>the Kuru-bulgar and Konövitza redoubts, built in 1876 during the Serbo-Turkish war.
They were all earthworks with a high profile, as was the custom at the time, and now had limited war value, so they were abandoned and progressively blended into the landscape.
The Army General Staff began to directly face up the problems related to the defence of Sofia in 1890. On the initiative of the Military Minister col. Mihail Savov, a special commission was set up. It was presided by the chief of the general staff lt.col. Racho Petrov, and it was composed by the staff officers major Stefan Paprikov, Nikola Ivanov, Krastju Marinov and Mihail Andreev. Their task was to study how to defend the country from an enemy coming from west. They examined many alternatives for the construction of fortified lines in the area of Godech, Slivnitza and Dragoman. Different plans were proposed such as the construction of reinforced concrete fortifications, earthworks, the use of the natural defence offered by the mountains, and so on.
Prime Minister Stefan Stambulov suggested to consult gen. Henri Brialmont, a well-known Belgian fortification specialist. Therefore, col. Nikola Ivanov, the deputy chief of staff of the Army, went to Brussels to discuss the matter with him. Brialmont the immediate protection of Sofia the construction of an expensive reinforced concrete fortification, to which Belgian companies were interested, although the progress of the war technique might make them useless or ineffective, even before its completion.
The reference model was the defensive belt of Bucharest, recently designed by general Brialmont (1883), in particular, the commission examined a quadrangular fort equipped with thick concrete protection (type 3 of the Bucharest fortress). To reduce the cost of the work and simplify its construction, it was decided to introduce various modifications to the initial project and to considerably reduce the thickness of the concrete walls.
The plan of the new fort was quadrangular, the external trapezoidal ditch became triangular with ramparts parapets. The trenches were shelled with frontal infantry fire and with light 57mm guns in armoured cupolas, placed in the corners (in concrete nests d). In the middle there was a concrete barrack (k), on each side two barbettes with emplacements (b) for 12cm or 15cm fortress guns, separated by small (n) or large (m) traverses. Overall, compared to the original one, the new structure of the fort was extremely simplified.
The commission decided to defend the north-western sector, placing the fort in front of the Vladaja-Buchino gorge and the Lom-Vratza road. The construction began in the summer of 1891 and proceeded slowly: by February 1895, only three forts had been built, but not yet armed. The other four were completed by the end of the century. Although it was planned to arm each fort with four to six heavy fortress guns, they received only 57mm QF guns for the close defence. The forts were built at Mramor, Iljantzi, Vrbnitza, Obelja, Filipovtzi, Konövitza, Leulju. Except Konövitza and Leulju, all the fortifications were placed on small heights. The distance between the forts was 2-8 km, and from the fortifications to Sofia was 4-9 km.
The decision not to protect Sofia with a powerful belt of forts like that of Bucharest was linked to the Bulgarian military doctrine of the time, which relied entirely on the manoeuvre. It was confident that a modern army with a powerful penetrating force would be able to protect the country’s borders without locking itself in fortifications. For this purpose it was enough to have temporary fortifications and some concrete strongpoints, mainly intended for ammunition. For the immediate defence of Sofia it would have been enough to control the Vladaja gorge, the Petrohan pass, the roads that passed through there and the Orahnie road, which cuts the Vakarel hill. A good protection of these approaches to the capital would have prevented the penetration of a large enemy force in the plain of Sofia.
Therefore, at the beginning of the 19th century plans began to be drawn up to extend the defensive line of Sofia. In 1901, Captain Simeon Dobrevski submitted to the engineering inspection a project, which included Vitosha and Ljulin in the defence system of the capital. The Inspection forwarded it to Army Headquarters and in 1904, it was formalized in the Project for the fortress of Sofia, which, however, remained only on paper.
During the inter-allied war and the First World War, the defence of the capital was integrated only with minor field fortifications.
Turkish fortification of Sofia in 1879
Type 3 Brialmont fort
Bulgarian revision of the Brialmont fort