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AOAV: all our reportsWide-Area Impact ReportAn Anatomy of a Mortar Strike

Explosive weapons with lack of accuracy: mortars (M-1943/M43)

This report is part of a series of case studies that make up an analysis of the wide area effects of certain explosive weapons and the concern about their use in populated areas. The report – Wide-Area Impact – can be read here. A video of mortar use can be seen here. An infographic covering this form of weapon can be seen here.

Mortars fire distinctive fin-tailed munitions from a smooth-bore tube mounted to a base plate on the ground. As soon as the mortar round is dropped down the tube it is launched at a high trajectory that can clear obstacles such as tall buildings or hills.

This ballistic trajectory means the weapons are not pointed directly at the target and fired. Instead, they are ‘walked up’ to the target. Each time a round is fired and misses, an observer is nearby to report where the rounds have landed so that the mortar crew can make necessary corrections.

Mortars have a high rate of fire and they are commonly used in rapid, intense bursts with several mortars being launched in short succession. Mortars are extremely widely used and produced. According to Small Arms Survey, nearly 50 countries have manufactured one or more types of mortars – with 30 continuing to do so as of 2008 – making it the most widely produced light weapon.

Mortars range in size and power and generally cover three categories: ‘light’ (up to 60 mm), ‘medium’ (61 mm to 82 mm), and ‘heavy’ (83 mm to 120 mm). In Syria in 2012 evidence surfaced of the use of a 240mm mortar bomb, but the most common sizes include 81/82mm and 120mm mortars.

One of the many mortar types in use in Syria is the M-1943. Syria has hundreds of these, which have been shipped to the country over the years by Russia and Bulgaria. The M-1943 is a heavy 120mm mortar. It is 0.66m tall, and weighs a little over 16kg. This weapon has a thick metal case, and only 2.68kg of high explosive TNT. The M-1943 can be fired as far as 5.7km. Its blast range is estimated to be around 28.44 sq m.

The classic mortar system in use by many armed forces across the world is notoriously imprecise. The dispersion of indirect-fire weapon systems is generally expressed using Circular Error Probable (CEP). This is defined as the radius of a circle within which half of all the weapons fired are expected to fall or explode. If a mortar system had a CEP of 100m, this would mean that, if eight mortar rounds were launched at a target in the middle of a circle measuring 100m, only four would land inside. This definition does not provide a full indication of accuracy. In this hypothetical example, the other four outliers could land immediately outside that distance or far away.

Despite technological advances that have improved accuracy of the most expensive and capable models, most conventional, unguided mortar systems have relatively high CEPs for such a short firing range.34 Conventional NATO High Explosive 120 mm mortar bombs have a CEP of 136m at their maximum ranges if an advanced fire control system is not used.