Old forts

The old forts of the Odrin dated back to 1877 and were only slightly reinforced after the so-called “artillery crisis” of 1885. In 1912 five of them had been declassed and employed as depot. Since they were placed on the crests, they were clearly visible from distance and were often employed by the Bulgarian artillery to adjust its fire. 



Karagös Tabia



Trace. In general they had a polygonal shape, with the head front curved outwards, two lateral fronts parallel to the central redoubt and the gorge front perpendicular to it.  Most of them were trapezoidal in shape, some semicircular, one circular (X) and two circular with a triangular outwork (ravelin) in front (XIII and XX).

Profile. The firing line was 4-5 m height; the thickness of the parapet was from 4.5 to 6.5 m. The forts were surrounded by a ditch, 4-5 m depth and 5-10 m width, without scarp and counterscarp covering, their banks being stiffened as soon as the ground allowed. Above the counterscarp some forts had a covered way, usually protected by traverses of earth bags and provided with wooden shelters of German type, dug into the glacis. Sometimes they were covered by a plate of corrugated iron. The ditches had no flanking works and were exposed to the enemy fire, being entirely in the dead angle without any protection.

Defences. The forts were defended only by infantry, exceptionally supported by some old machine guns. The ramparts were originally arranged only for open air artillery emplacements. Therefore it was almost impossible for the defenders to serve their guns under the enemy fire, and in 1912 the Turks had remove all their guns from all the forts, except for new Taš Tabia, placing them in flanking batteries. The main rampart had 3-6 traverses exceeding the crest of the parapet by 1-1,5 m. Many traverses covered a vaulted shelter, 60 cm1 m thick, made of brick or stones. Some forts were arranged with two, occasionally also three, lines of fire, by raising a cavalier on the rampart. The covered ways were usually well conformed to the ground, and sometimes were not parallel to the firing line. The bulk of the troops charged of the forts defence were kept behind, in concrete or wooden shelters, in tents or in barracks, leaving only a little detachment as permanent garrison. The interval between the forts was covered only by the infantry firing from the lateral fronts and by the direct fire of the troops in the trenches and batteries, linking the forts. 

Shelters. The shelters were composed by the casemates built under the traverses of the forts and by the housing buried under the rampart of the gorge front. The casemates originally planned to lodge the garrison, in 1912 were usually employed as ammunition depots. They were made of brick or stones, with vaults 60 cm1 m thick near the keystone. The housings of the gorge front were entirely covered by earth and were ventilated only by vertical vents, debouching above the ramparts. Their entry was placed sideways, on the left and on the right of the entry of the fort. In addition there were the wooden shelters of the glacis.

Communication. The entry of the fort, 4-5 m wide, was on the gorge front, the rampart being cut by vaulted postern or, more frequently, simply by an open passage. The gorge ditch was interrupted in front of the fort entry. Outside it was protected by an outwork for the infantry, with the form of an arc or, at Aivas Baba, of a triangle, but without any kind of hindrances before. Inside the forts the ways communication were uncovered, the inner terre-plein was connected with the fighting positions by means of ramps.



Aiži Yolu Tabia


a. vaulted shelter protected

by an earthwork 

b. opening 

c. stone walls

d. inner terre-plein

e. head front of the fort



New Forts

Trace. Even if designed forts, they were actually lunettes, having no gorge front and therefore no defence on the back. They were simply trenches with a straight head front with two sides as lateral fronts.

Profile. The height of the firing line was usually weak, being not higher than 1 m, the slopes, with an inclination from 1/6 to 1/10, were prolonged below the ground. A grid of barbed wire placed on the slope, surrounded the head and the lateral fronts. Behind the fighting position, an inner trench, 2 m wide at the utmost, was employed as communication trench. There were no flanking works, like in the old forts.

Defence. The forts were defended by infantry, kept in concrete shelters placed under the parapet, 40-50 cm thick. They were not made by true reinforced concrete, as the Bulgarian Army thought, since only the top of the shelter was reinforced by a trellis of 8mm iron wire, while the front and the lateral walls did not have a metal structure. They were closed by wooden doors. The fighting position was provided with traverses both covered by earth and made by earth bags. During the combat, the troops were deployed behind the traverses placed between the shelters. In some forts a machine gun was installed in the corner angles (salients), protected by semicircular parapets reinforced by earth bags.

Shelters. Beside the concreted shelters of the parapet, the garrison was lodged in concrete shelters placed behind the forts, just below the crests.

Communication. The links between the outworks and the forts were out of the enemy sight by means of the ground features or protected by communications trenches. In the forts themselves the trench behind the firing position allowed the troops to move without danger. At the ends of the forts some ramps connected the bottom of the inner trenches with the level of the ground.



a. Nordenfelt machine-gun

b. plank support 

c. earth bag covering

d. concrete shelter

e. frame of the closing

g. inner terre-plein

h. crest

i. strem

Salient at Kasan Tepe



Connecting trenches

The connecting trenches had a weak profile, being high only 80 cm, with the slope prolonged till the level of the ground. They had only wooden shelters, whose roof was usually a plate of corrugated iron 2mm thick, covered by earth, in order to protect the troops against the shrapnel bullets. Sometimes in the rear there were covering trenches linked with the first line for the communications. To deceive the enemy, the Turks had also built some fake trenches before the interval between the forts.



a. shelter at battery 38

b. Maxim machine gun

c. Nordenfelt machine gun