The familiar mortar tube or barrel is only part of a total weapon system and to get rounds on target is a far from simple business, although it is considerably less complex than artillery gunnery.

Mortars are one the oldest forms of ordnance and can trace their ancestry back to breech-loaded medieval siege mortars. The development of rifled artillery in the 19th Century seemed to make breech loading ordnance obsolete, but the requirements of World War One trench warfare resulted in something of a renaissance: the need for simple weapons to lob shells on very high trajectories into enemy trenches prompted the development of trench mortars. They used a smooth bore metal tube as a barrel and were supported by an A-frame, which could be used to raise or lower the barrel to adjust the fall of shot. Today’s mortars are essentially similar in concept but considerably more sophisticated.

The role of tubes and frames is self-evident. Their design and materials determine the range and rate of fire of the weapon. Often the heaviest item is the base plate, which provides the weapon with the stability needed to absorb the recoil and keep it pointing in the same direction. As a matter of fact, the base plate is the element that requires the highest degree of know-how in design and manufacture, and many of those who have tried to copy popular designs, like some of the TDA models for example, by so-called reverse engineering process have often failed lamentably.

There are three main types of mortars: platoon mortars of 60 mm calibre, 81 mm to 82 mm for battalion work and 120 mm heavy mortars. The former two are usually man-portable and the later are nearly always vehicle borne or towed.

Sights are an often neglected area of mortar design. As an indirect fire weapon, mortars do not use sights to aim at targets but are designed to keep the weapon aligned with a nominal aim point and ensure that the crew can compensate for the mortar bedding itself in to the ground after each successive round is fired. Most mortars lack the recoil mechanisms of artillery pieces so this can be a major problem during sustained fire missions.

Mortar ammunition comes in many varieties, with standard rounds including high explosive, smoke of various colours, illumination, anti-armour and training types. Increasingly new types of round are becoming available, including smart terminally guided weapons, submunition dispensers and rocket-assisted rounds. A variety of fuses are used to provide impact or other detonation effects.

Propellant charges are an important part of the mortar system. Conventional mortar bombs are not fitted with cased charges, like small arms and much direct fire weapon ammunition. Mortar crews have to place propellant charge bags or packages around the base of the round depending on the range required. Ignition charges are relatively simple elements that have a significant impact on performance, causing misfires or affecting range.

Target information, received by radio from observers, needs to be quickly turned by the operators into a bearing and range from the mortar base plate position. Now, pocket-sized calculator type devices do the job.

Developed by Mechem (Denel Group), this pocket-sized fire control system is seen here in the hands of the South National Defence Force.

Mobility for mortars is important if they are to keep pace with advancing friendly troops and allow them to move to avoid enemy counter battery fire. The big debate is between man-portable and self-propelled systems. A major issue for mortar crews is the packaging of ammunition. Complex packaging can have an adverse effect on the rate of fire of mortars but flimsy packaging can result in rounds, fuses and, particularly, charges being damaged.