Rules for firing in fortress-siege artillery

Till 1897 the Bulgarian fortress-siege artillery had not special rules for firing, the only direction existing was the so called “Red booklet”, published in 1889 and specifically directed to the field artillery. Their need was greatly felt by the Bulgarian military circles, the European literature was carefully examined and the first original proposals were made. Detailed “Draft rules for firing with siege, fortress and field mortars batteries” were published by cpt. Atanas Rakovski, the commander of the Sofiyski fortress battalion, in the Военен Журнал in 1893-95, considering every kind of fortress artillery piece utilized at that time by the Bulgarian artillery and dealing with every aspect of the matter, from the different methods of firing to the signals for transmitting the orders during the combat.

In 1896 with the creation of an independent direction of the fortress artillery under to active leadership of col. Nikola Ryaskov, the situation begun to change. On 18 February 1896, with his Order N° 5 he listed in detail the reasons of the failure of the training fires made by the fortress battalions : 1) the officers were not well trained, since they had been recently transferred from the infantry battalions or the field artillery batteries; 2) the firing rules had been not adequately assimilated by the gunners; 3) the knowledge of the artillery materials recently introduced in armament was inadequate; 4) there were not manuals to instruct the troops in the service of the piece and in the conduct of fire.

First Проекто-правила за стрелбата въ крепостно-обсадната артилерия (Draft rules for firing in fortress-siege artillery) were elaborated by the direction of the fortress artillery in 1897 and sent to the battalions to be tested. After three years, they were revised according with the remarks and the proposals of the officers, who had applied them during the training firing practices, and published with Order N° 26 on 17 October 1900. Nevertheless also this text was regarded as provisional and after only two years it was replaced by a new Наставление за стрелба въ крепостно-обсадната артилерия (Direction for firing in fortress-siege artillery) that was mainly work of maj. Ivan Vatev, the head of the technical section of the Artillery Inspection.

The rules of fire were mainly based on the “Red booklet”, with only some changes due to the experience gained from its issue and to the typical features of the fortress-siege artillery pieces. The Draft rules exposed also a system to transfer the fire quickly, but did not contemplate special rules to direct the fire of a group of batteries, even if it was improvised by the Bulgarian artillery at that time.

Fortress artillery pieces could fire with different battering charges in order to make the trajectory more or less curved and hit also troops protected by trenches or breastworks.

- aimed fire : it was executed by long guns firing with the maximum charge, using all kinds of projectiles – shell, shrapnel and case shot; its performances were the highest accuracy, high horizontal striking velocity and the highest flatness of the trajectory;

- plunging fire : it was executed by howitzers and mortars firing with reduced charges at high angles, using shell or shrapnel; its performances were high steepness of the trajectory and high vertical striking velocity;

- jumping fire : it was executed by short guns firing with mid charges at mid angles, using shell or shrapnel, its main performance was a trajectory steep enough to jump over the obstacle and strike the target placed behind it with sufficient force.

The adjustment was usually made with shell, according with the process described in the “Red booklet”, i.e. 1) taking the target into the high bracket, 2) shortening the bracket by halving to obtain the low bracket, 3) repeating the limits of the low bracket, 4) firing at one of the limits or at the middle of the low bracket, 5) verifying the height of sight obtained by firing a group of six shots.

However the low bracket could be reduced up to 4 probable errors, instead of 2, since the practice fires had showed that the deviations reported in the firing tables of the Russian guns were often wrong. In fact the tabular deviations of the 6 inch mortars were 2-3 times greater than the real ones, whereas the real deviations of the 4 pdr and 9 pdr guns were much greater that the tabular data. The bracket of 2 probable errors was required only with howitzers firing at high angles, especially with an angle of 38°, in order to fire with the established charge.

The limits of the low bracket were repeated since the fortress-siege artillery fire should be methodical and accurate. Repeating the limits the probability of hitting the target raised to 83%, instead of only 53%. The repetition slowed down the rate of fire, but this was not so important since the targets of the fortress artillery were not transitory like those of the field artillery.

The adjustment with shrapnel was usually made beginning with shells and shifting to shrapnel as soon as the burning time of the fuze was set. For this purpose the Draft rules introduced more accurate indications to find the correspondence between the elevation and the fuze set. Exceptionally the adjustment might be made also directly with shrapnel. With shrapnel fire 2 control rounds should be shot every time a doubt arose about the accuracy and effectiveness of the fire or also to verify whether the target had changed its position. If the enemy could suffer from the control fire, it is possible to shot even a whole battery discharge 4-6 rounds). Control rounds should be shot at an elevation increased of two low brackets and with fuze set for low bursts.