Mortars are weapons typically designed to fire in the high trajectory (over 45 degrees) and have generally been smooth-bore and muzzle-loaded systems with short, light tubes, relatively low muzzle-velocities, and a high rate of fire. They lack recoil systems, transferring the force of the recoil into the ground. Although the US Department of Defence defines a mortar as being muzzle-loading, automatic breech-loaded mortars appeared 40 years ago in fortresses, and in the 1980s the USSR produced a breech-loaded mortar to fire in both the low and high angle.
Mortar bombs have a lower velocity than artillery shells and are subject to lesser forces on firing. They can therefore contain a higher proportion of explosive, but being of low velocity and not directly aimed at a target, mortar bombs are least effective against armour, and most potent against soft area targets. They are also effective against targets such as entrenchments. The time of flight of a bomb is longer than that of a shell and mortar fire is therefore subject to greater meteorological variation, making it less accurate than shelling by guns or howitzers and less likely to hit a moving target. Emerging technology is now redressing some of the mortar's disadvantages. Mortars have tended to be cheap and simple but mortar bombs can now be given rocket assistance, increasing their range without requiring significantly greater weight or expense in the mortar itself. Mortars have been most easily located by radar calculating the point of origin of the bomb by comparing two points on its trajectory, but bombs which have a trajectory distorted by rocket assistance should be harder to detect. Mortar bombs with terminally guided ‘smart’ fuses can now hit armoured vehicles with precision from above, a hard-target kill capability to rival more expensive and sophisticated weapon platforms.
Mortars were originally developed for siege warfare to lob munitions over walls and other fortifications. They were first used by the Turks at the siege of Constantinople in 1451 to attack the enemy fleet. They tended to be heavy and immobile, but in the American civil war were transported for the first time on railway mounts. Mortars were used in coastal defence to attack armoured battleships from above and were also mounted in ships to attack shore fortifications, for example the bombardment by the Royal Navy of the Russian fort of Sweaborg in August 1855 and the attacks on Russian river forts by the British and French in October 1855. By the beginning of the 20th century, the siege mortar had been transformed into a short-barrelled, breech-loaded howitzer. Giant mortars/howitzers, usually mounted on railways, were used by the Germans to reduce the fortress of Liège in 1914 and in the siege of Sevastopol in 1941-2. By the mid-1980s the USSR had deployed self-propelled (SP) mortars of up to 240 mm designed to demolish NATO strong points.
In WW I, armies developed lighter infantry mortars for use in the trenches, based on the British 3 inch Stokes mortar of 1915. These became standard issue in most armies and thereafter a distinction was made between artillery mortars and infantry mortars. High explosive shells were largely ineffective in cutting wire in WW I and in the British army this became the major task for mortars from the battle of Arras/Vimy Ridge, April 1917, onwards. Between the world wars, the infantry of most nations sought to introduce their own anti-armour guns and mortars to provide what Wavell called ‘self support, not close support’. The British army was so impressed by the German use of mortars in France in 1940 that it trebled the number in its own battalions. By 1944, Allied artillery had largely mastered German artillery and the mortar, which was more mobile and harder to detect, became the greatest threat to Allied infantry in Normandy, accounting for an estimated 70 per cent of British casualties. The Germans usually placed their 81 mm mortars 547-875 yards (500-800 metres) short of their opponents' positions, making it hard for the Allies to return fire with artillery or mortars without endangering their own men. A sophisticated counter-mortar organization was developed and for VERITABLE, the battle for the Reichswald in February 1945, this linked observers, detecting radar and counter-fire units. The Soviets made great use of mortars in WW II, the Germans having nothing to match their 160 mm piece. When attacked by it for the first time, they believed that they were under air attack. Mortars were so useful in the Burma campaign that, after April 1945, many anti-tank units of the British army were converted to 3 inch and 7.2 inch mortars. US Under Secretary of State for the Army E. D. Johnson claimed that mortars caused most of the casualties in the Korean war.
Where artillery support cannot be guaranteed, mortars have come to be regarded as the infantry's organic source of fire, particularly for parachutists, mountain troops, and irregulars who lack heavy equipment. Where the infantry has been mechanized, so mortars have been mounted in armoured vehicles or towed by trucks to accompany them. The ranges of these heavier mortar systems now rival light artillery, reaching over 10 miles (16 km). The tactical mobility, range, and lethality of mortars have made them ideal weapons for guerrilla warfare in numerous African conflicts, during the Vietnam war, in Afghanistan in the 1980s, and by all sides in the Bosnian conflict of the early 1990s. Home-made mortars have also been the most effective weapon employed by the IRA against British security installations in Northern Ireland since the 1970s and, on one occasion, against the British PM's house in Downing Street.
Bibliography
- Bailey, J. B. A., Field Artillery and Firepower (Oxford, 1989).
- Bellamy, C., Red God of War, Soviet Artillery and Rocket Forces (London, 1986).
- Fowler, W., ‘Mortars—The Infantryman's Artillery’, Defence, 17/8 (Aug. 1986).
- Kershaw, A., Weapons and War Machines (London, 1976)
— Jonathan B. A. Bailey
