The fortress of Odrin

During the Russo-Turkish War of 1877, the Russian Army conquered Odrin (Turkish Edirne, Greek Adrianopolis) after a brief siege. At that time the fortress had a girdle of 24 forts and batteries, without connecting trenches, of which 19 were on the hills and 5 in the plains. The main line of defence, composed by 20 forts, was located 500 (Kaik) to 5000 m (Aivas Baba) out from the city centre, and their mutual distance was from 1500 to 3000 m. They were constructed upon the plans and under the supervision of Blum Pasha, formerly an officer of engineers in the Prussian service.

There were 4 advanced forts, 2 in the North-western Sector (Kazan Küprü and Karagöz Tabia) and 2 in the North-eastern Sector (new Taš Tabia and Kavkas Tabia). They were lunettes, defending the lines of approach to the fortress that were not covered by the fort of the main defence. The ground of the Western Sector was so swampy, that it was impossible to attack there. Therefore there was a 3500 m gap between Maras Tepe and Kazan Küprü. The city itself had no enceinte.

The prevailing type was a circular redoubt, sometimes containing a cavalier or a redoubt, with traverses containing bomb-proof magazines between each pair of guns, surrounded with a polygonal ditch with banquette for infantry fire. The gorge was closed by an exterior traverse in the form of a semicircle, usually arranged for one gun and for infantry fire.

Before the outbreak of the Balkan War, 5 of these forts had been declassed: Čatal Yolu, Čaj Tepe (North Western Sector), old Taš Tabia and Kokardja (North eastern Sector) and Merkes Tabia (Southern Sector). Further 19 forts were still operative in 1912, when in North Eastern Sector they represented the most important works of the line of defence.

In 1878 the Berlin treaty established a strong Bulgarian state immediately on the strategic doorstep of the city, with the new frontier a mere 24 km from the city’s centre. In 1885, when Bulgaria became stronger and its army more capable, the Turks became more concerned with the security of Odrin antiquated fortifications. With German assistance, the Ottoman General Staff began planning a significant upgrade in the defences. In concept, the new fortifications were to be based on an interlocking series of strong points (small, self-contained forts) located concentrically 3 to 4 km out from the city centre. Nine strongpoints were planned, each containing an infantry detachment, six machine guns, and either four field artillery pieces or three howitzers. The strong points were built mostly of brick or stone, and the gun positions had embrasures providing overhead protection. The strong points were fronted with earthworks and linked together by an underground telephone system.

Inside this girdle of the strong points, the Turks planned to place numerous batteries of artillery. But they did not have nearly enough artillery for this ambitious scheme, and immediately purchased 12 – 150mm howitzers, 5 – 150mm guns, and 12 – 105mm guns from the Germans. In addition they brought in 87mm guns from the Second and Third Armies. Other physical improvements were made as well, including macadamizing the interior roads and constructing bombproof magazines. Finally, in February 1910, the improvements were completed and the fortress achieved its “first form.”

However, in that year General von der Goltz, who was on an inspection tour during manoeuvres, stopped at the fortress to examine the improvements. Keenly aware of the changing tactical dynamic, von der Goltz recommended that the defensive arrangements for the city be changed by moving the strong-point system farther out, to key terrain located 3 to 8 km from the city’s centre. These changes would result in what the Turks called the fortress’s “second form.” Unfortunately, the Italian War put this idea on hold temporarily and, in 1911, Odrin actually lost a battery of 105mm guns and 12 – 90mm guns that were sent to the Dardanelles and Bosporus defences.

In 1912, during the reorganization of the Ottoman Army, Odrin became the home garrison of the newly organized IV Army Corps under the command of Ferik Abuk Ahmet Pasha. The new commander was very interested in the second-form project, and assigned staff major Fuat and staff captain Remzi to work with German technical advisors and fortification experts on planning the new system. The new plan was ready in April 1912, and work began immediately to move the strong-point system farther out from the city centre. The new system had a total of 18 strong points or redoubts, most of which were located on small hills or ridgelines that dominated the surrounding terrain. The plan called for the strong points to be linked by trenches and barbed wire.

The Turks thought that the plan would take four years to complete. Although work had begun and had accelerated as the empire drifted toward war, the system was incomplete by 1 October 1912. On that date, some of the strong points had been completed (Yildiz, Karagös, and Aivas Baba), but most were incomplete. Pressed by the imminent war, the fortress commander concentrated on the construction of the trench system linking the strong points.

The peacetime garrison of the city and fortress consisted of the IV Corps headquarters, the 10th Infantry Division, the 4th Rifle Regiment, and corps troops. Strong cavalry forces for the screening of the frontier were also located there and consisted of the 4^th Cavalry Brigade (9^th, 10^th, 11^th Cavalry Regiments) and the 5^th Light Cavalry Brigade (1^st and 2^nd Light Cavalry Regiments). The Fortress Artillery Brigade was extremely powerful, and was composed of the 6^th, 7^th, 8^th, 9^th and 10^th Heavy Artillery Regiments.

On 18 October 1912 the fortress had mobilized 926 officers and 50,650 men, but on the 21 October 1912 the unplanned attachment of the 11^th Infantry Division to the fortress brought the total personnel strength up to 1,111 officers and 60,139 men. The large size of the garrison belied its combat readiness, as only about 25 % of the men were regarded as trained and many reserve officers were lacking in tactical proficiency as well.

The garrison was composed by :

– Nizam (first line) troops : 10^th and 11^th Infantry Divisions and 4^th Rifle Regiment;

– Redif (reserve) troops : Edirne, Baba Eski, Gumülcine Divisions;

– 12^th Cavalry Regiment;

– Six machine-guns detachments with 24 Maxim machine guns;

– Fortress Artillery : 6^th , 8^th, 9^th (with 3 battalions and 12 companies each), 7^th (with 2 battalions and 8 companies, 10^th (with 3 battalions and 13 companies) Heavy Artillery Regiments – 57 companies.

In 1913, after the recapture of the fortress, Turkish Army decided to reconstruct the permanent works which had been much damaged by bombardment and to enlarge the perimeter especially on the east side. At the beginning of the World War Edirne was armed with only 115 guns:

70 – 150mm short guns;

11 – 150mm mortars;

8 – 120mm guns;

10 – 120mm howitzers;

16 – 87mm field guns.

But in September 1915 the treaty with Bulgaria and the cession of the Maritza line made the fortress useless and untenable, and some of the forts were dismantled. Great part of the fortress troops with the artillery that could be moved was sent to Chataldzha, the Dardanelles and Uzun Küpru.

Odrin in 1906	1910 plan	1912 plan