Mortars. The mortar is a very simple piece of artillery, essentially a firing tube, that fires a high arc and imparts its main recoil force directly into the ground through a base plate. The lack of a recoil system distinguishes this weapon from other pieces of artillery. Dating back to at least the fifteenth century, mortars became most common in World War I. With opposing forces dug in at close ranges, a simple weapon capable of high‐angle fire was needed to drop rounds in the enemies' trenches. In Britain in 1915, Sir Wilfred Stokes produced the prototype that has become the world's standard, consisting of a tube with a fixed firing pin at the breech attached to a base plate and supported at the muzzle end by a bipod. It can be adjusted in both azimuth and elevation by a screw mechanism. To fire the weapon a projectile containing the propellant and explosive is dropped into the muzzle.

After World War I, mortars passed into the hands of infantry units, while very heavy pieces remained with the artillery. The U.S. Army classifies mortars as light (60mm), medium (81mm), and heavy (120mm and above). All light and medium mortars are carried by infantrymen. They are inexpensive and easy to maintain, and can achieve a very high rate of fire. An 81mm mortar platoon can fire 196 rounds in a minute—a far greater weight of ammunition on a target than can be achieved by a field artillery battery, but one that can only be sustained over a short period of time. Concealment is easy and fire control is straightforward. With the advent of global satellite positioning systems, accuracy has been improved. The high‐angle fire associated with this weapon allows it to engage targets concealed behind cover.
[See also Weaponry, Army; World War I: Military and Diplomatic Course.]

Bibliography

The Diagram Group , Weapons: An International Encyclopedia from 5000 B.C. to 2000 A.D., 1990.
Timothy M. Laur and and Steven L. Llanso , Encyclopedia of Modern U.S. Weapons, 1995.

William F. Atwater