Siege and fortress artillery



In 1885, after the defeat of Serbia and the union of the Eastern Rumelia with the Principality of Bulgaria, the main aim of the Bulgarian policy was to liberate the brothers living in Macedonia under the Turkish yoke. But a war against Turkey meant to face the fortress of Odrin, which could be regarded as the most powerful strongpoint in the Balkans. At that time the Bulgarian Army had only a little number of old Russian heavy guns delivered in 1878, after the end of the liberation war. Besides 12 – 6 inch mortars and 17 – 24 pdr short guns, the only quite modern guns were 6 – 120mm L/25 Krupp guns, for which however there were no shells available. They were stored half in the arsenal of Ruse and half in a museum in Pleven, and only in 1896 they were assigned to the Sofijyski fortress artillery battalion, after having purchased the required ammunition.


To equip the fortress artillery with modern weapons, in 1890, on request of the Prime Minister Stefan Stambulov, the government announced funds to buy 150mm Krupp long guns. The order was assigned to the Artillery Inspection that sent to Essen a commission to test the heavy guns manufactured by Krupp. The commission suggested buying also 120mm long guns. The government approved the report of the Military Minister and on 23 March 1891 a contract was signed with the German firm Krupp to obtain 14 – 150mm L/30 guns and 12 – 120mm L/30 guns with their equipments and ammunition. They were delivered between the autumn of 1892 and the beginning of 1893 to be employed as siege weapons against strong earthworks at long ranges.

These guns were intended for use on a wooden platform, the carriage being connected to a pivot plate on the platform. The platform consisted of three layers of posts connected by bolts, on which also a shield was fastened. Even if they were not true quick-firing guns, a recoil buffer was connected from the platform to the trail and wooden wedges behind the wheels were used for counter-recoil. These wedges both took up the recoil and made the task of manhandling the howitzer back into position easier. According with some Western sources, two of these guns were later equipped with steel wheels type Bonagente, in order to increase their mobility and allow them to fire without being mounted on the platform. This is confirmed by a picture.


In 1891 major Nyagul Tzvetkov was sent to the German firm Grusonwerk at Magdeburg to test the 57mm fahrbare Panzerlafette (“movable armour carriage”) or Fahrpanzer (“mobile armour”). It was a quick-firing gun mounted in a mobile armour housing especially designed as fortress weapon, being regarded by as “very advantageous for use in the construction of temporary fortifications or entrenchments”. It was introduced by Grusonwerk in 1886 after the design of Maximilian Schumann (patent n° 367,617). It would be mounted on a narrow gauge railway track protected by being in a shallow trench or behind a low parapet. It would be located at one end of the track concealed by stone, concrete or earth works. As and when needed (say to repel a storming attempt) the Fahrpanzer could be trundled out of hiding (using cables) to bring its gun to bear. For the transport of the gun on the road, the export version had a horse-drawn limber carrying two smaller wheels forward, while the German Army used a two-wheel cart.

This kind of guns were sold in significant numbers to various countries (Romania, Denmark, Belgium, Switzerland, Chile) both in 57mm, 53mm and 37mm calibre. In summer 1891 Grusonwek started a tour aimed at publicizing their new guns in the Balkans. Exhaustive tests with a 53mm gun were carried on at Belgrade in May, and on 22 and 24 June at Sofia. They were repeated on 8 and 9 December at Hademköi, near Istanbul, with a 57mm gun, the results being always excellent, as reported by the European artillery journals (Revue d’Artillerie, Reichswehr, Militär Wochenblatt, Mitteilungen über Gegenstände des Artillerie-und Genie-Wesens).

On 25 May 1892 the Artillery Committee and the Committee for the defence in a joint session considered what kind of quick-firing gun was most suitable for the close defence of the forts of Slivinitza, Belogradchik and Vidin. As for the ballistic characteristics, the 75mm gun was superior, being effective even at a range of 2000/2500 m, but the 57mm was more movable and could concealed more easily. Then, since its fire was very effective at a range of 1500 m or lesser, and it should be employed mainly in close combat, the 57mm was choosen and 30 Fahrpanzer were bought. They arrived in Bulgaria in 1892-93, after the firm Grusonwerk had been purchased by Krupp, the takeover agreement having been signed on 10 December 1892.

In the same years major Kalin Najdenov was sent in Germany, France and Great Britain in order to test the new artillery weapons produced by the most important European firms. On his return he published on the Военен журнал (“Military Journal”) some detailed articles, where he reported his opinion about them. Another important member of the Commission for the adoption of modern weapons in 1893 was lt. Vladimir Vazov.


In 1896 War Minister Racho Petrov along with some officers came to Bucharest to study the fortification works of the Romanian capital. Impressed by the steel cupolas built by Schneider, St.Chamond, Chatillon & Commentry (Montluçon) and Gruson, he inquired whether a French group would come to Sofia. Therefore the French Minister in Sofia, Maurice Michel-Schmidt, considered that a double effort by Creusot and Canet would possibly lead to an order of new war material for French industry, especially after the Bulgarian politician Nikolov had requested a study of gun from Creusot.

On 30 July 1896, a Franco-Austrian group composed by Banque de Paris et des Pays-Bas, Banque Internationale de Paris and Länderbank, issued on the French market a loan of 30 million franks on behalf of the Bulgarian government. In that occasion – end 1896/beginning 1897 – Eugène Schneider visited Sofia and designated an agent for Bulgaria, while previously the Schneider agent in Vienna had to take care also of the Balkan States. This decision clearly showed the intention to enter in a market until then reserved to the Germans. In fact, among the conditions imposed for the admission of the loan on the Paris bourse, the banks placed the demand that the French firm Schneider-Canet receive an order for 120 artillery pieces.

The Bulgarian government would have preferred to keep on buying Krupp guns, since they had served as the standard guns in use by the Army since the beginning. Nevertheless to appease the French Foreign Minister Gabriel Hanotaux, who had intervened directly in support of the French firm, it agreed to place a smaller order : on 10 February 1897 Schneider-Canet obtained a command for 24 siege guns, 24 heavy howitzers and 18 mountain guns for 1,250,000 levas. Schneider had to supply both the guns and their ammunition and equipments (cast iron shells, steel shells, steel shrapnel, propellant charges of black powder for guns, vent-sealing tubes of Bulgarian model, double effect fuzes for fortress guns and percussion fuzes for field guns).

It was only after that the contract had been signed, that the loan was issued in June 1897, and 3 million levas were made available for arms order. In this manner Schneider scored its first success in Bulgaria, and in April 1901 the first 23 guns arrived in Ruse, while the remaining ones were delivered within the end of 1902. Nevertheless Krupp still held the advantage, since in same year it received a larger order : 90 field guns with their ammunition, for the price almost double – 2,135,000 levas.


The planning and the manufacture of the French artillery pieces lasted from 1898 to 1900. They were tested under the control of some representatives of the Bulgarian Artillery Committee that required the introduction of alterations, when the pieces were still in the factory. To make the howitzers more movable, major Kalin Najdenov suggested to remove the platform planned by Schneider, and designed a special field wheeled carriage, which rendered them suitable for immediate service on any kind of ground without being necessary to construct a firing platform. In such a way the howitzers could be drawn by horses or oxen and placed in firing position quickly and easily. The carriage was provided with a trail spade that in ordinary ground prevented almost completely the carriage from recoiling. The recoil of the barrel in the cradle was absorbed by a hydraulic recoil cylinder, the return being secured by a compressed air run-out gear. Also the sight was improved, graduating it.


The innovative heavy howitzer resulted from the conversion was presented to the Paris International Exhibition in 1900. Unfortunately it was delivered hastily and without appropriate tests, and after being employed for two or three years the howitzers showed some major faults : in particular during the return in battery, the compressors let flee air and after 4-5 shots they broke down, forcing some pieces to interrupt firing. On 26 November 1904 the Artillery Committee examined the howitzers, suggested some improvements and subsequently commanded to Schneider the accessories required to modernize them on the basis of the Bulgarian plan. They were built in France, but were assembled in the Sofia Arsenal.

The improvements introduced were :

    the replacement of the air brakes with hydro-pneumatic ones, that prevented the leak of the air;

    the introduction of special gears for small lateral correction, that enabled to fire more easily and rapidly;

    the adoption of dual sights equipped with goniometers, that enabled to aim easily from covered positions;

    the introduction of elevating gears that enabled to put the barrel in horizontal position rapidly, when the howitzer was loaded;

    the addition of a movable trail spade and of devices to fixe the howitzer during the march and joint the traversing lever with the carriage trail.

In 1907, when the howitzers were finally fully upgraded, the fortress battalions carried several drills to test the weapons and train the troops. On the basis of the lessons learned, further improvements were introduced, this time to the 120mm siege guns. In order to increase their field of fire, an extension was added on the right or on the left side of the firing platforms. In addition to protect the guns and the crews from the shrapnel bullets they were covered and surrounded by a shelter, the so-called “veranda”, that proved to be very effective during the siege of Odrin.


At the beginning of the 20th Century the Bulgarian siege park could field 109 artillery pieces, including the outdated Russian guns and mortars. The general Staff intended to share the fortress guns among Vidin and Belogradchik : each of them should receive 8 – 150mm, 120mm and 24 pdr guns and in addition some old 4 pdr guns, Vidin 12 and Belogradchik 10. All the existing projectiles for them were collected in these two fortresses, since the supply of ammunition in wartime could be very difficult and it should be avoided the capitulation of a fortress due to the lack of ammunition.

In 1905 in order to strengthen the defences of the Odrin stronghold with a powerful mobile reserve of artillery, Turkey ordered 18 – 150mm heavy howitzers and 18 – 105mm long gun to the German firm Krupp. These modern artillery pieces outclassed the whole Bulgarian heavy artillery both in range and in fire power.

To manage this threat, in 1906 the budget of the Bulgarian War Ministry assigned a considerable sum to increase the amount of the heavy artillery. Then the Artillery Inspection proposed to buy 24 – 150mm heavy and 48 – 120mm field howitzers, but the Chief of the General Staff, major general Radko Dimitriev thought more urgent to buy mountain guns instead of heavy howitzers. The purchase of field howitzers dragged on, because the French firm Schneider-Canet at that time had not 120mm howitzers and proposed a 105mm light howitzer. In 1911, after a long debate, the Bulgarian Government ordered 36 howitzers instead of 72, as originally planned.


In 1909 Major General Georgi Vazov published a Brief instruction on the operation and the attack against fortresses (Кратко упътване за действие против крепостите и атаката им), where he presented a detailed introduction to the siege warfare and to the gradual or regular attack to a fortress. Unfortunately his text did not penetrate into the Bulgarian Army, and was studied only by the Engineers, to whom it was mainly addressed.

In the spring of 1911, lt.col. Stefan Slavchev, head of the Sofiyski Fortress Artillery Battalion, gave some lectures on the vital importance of the Odrin stronghold in a war against the Ottoman Empire. After a detailed analysis of the defensive works of the fortress and of the Bulgarian military equipment, he concluded that in order to attack Odrin successfully the Bulgarian Army should purchase 3 – 150mm heavy artillery batteries with 6,000 rounds each, 26 – 120mm howitzers batteries with 8,400 rounds each and 6 – 105mm long guns batteries with 500 rounds per gun, as well as 2,000 incendiary shells for 150mm and 120mm howitzers, 7 searchlights, 9 balloons and various engineers equipment. Lt.col. Slavchev thought that all this materiel would cost around 30,000,000 levas.

Unfortunately at the beginning of the Balkan War, nothing had been done to fulfil his plan. Also the request carried out jointly by the Artillery Inspection and the General Staff in 1910 to obtain funds to form a siege park composed of 300 modern artillery pieces was not accepted. To have an increase of its heavy artillery, the Bulgarian Army had to wait until the fall of Odrin in March 1913, when a large amount of fortress guns was captured and immediately adopted. Thus the major part of the fearful quick firing 150mm howitzers and 105mm guns of the Turkish Army became the top of Bulgarian Artillery.