Mortar (weapon)

A mortar consists of a smoothbore barrel, a base plate, and a bipod or other mount. It is fired by dropping a shell down the barrel, where a firing pin strikes the primer, igniting the propellant charge. The high-angle trajectory allows the projectile to drop vertically onto targets, making it effective against troops in trenches or behind cover.

Modern mortars come in three main categories: light (60 mm), medium (81 mm), and heavy (120 mm). They are typically crew-served, with a team of two to five soldiers. The weapon can be disassembled for transport, and some variants are mounted on vehicles or ships. The mortar's simplicity and low cost make it widely used by armed forces worldwide.

The mortar's origins trace to the 15th century, when European armies used short, wide-barreled cannons to lob explosive shells over castle walls. The name derives from the mortar and pestle, due to the similar shape. During World War I, mortars like the British Stokes mortar became essential for trench warfare, providing rapid, high-angle fire.

In World War II, mortars were standard infantry support weapons, with the U.S. 60 mm M2 and the German 81 mm Granatwerfer 34 being notable examples. Post-war developments introduced rifled barrels and improved ammunition, such as the Brandt 120 mm mortar, which remains in service today.

Mortar shells come in various types: high-explosive (HE), smoke, illumination, and precision-guided munitions (PGMs). HE rounds are the most common, with a typical weight of 1.8 kg for a 60 mm shell to 16 kg for a 120 mm shell. Modern PGMs, such as the U.S. M982 Excalibur (though primarily for howitzers), have inspired guided mortar rounds like the Israeli Iron Sting.

Specialized variants include self-propelled mortars (e.g., the U.S. M1064), recoil systems for vehicle mounting, and lightweight models for airborne forces. Some mortars are rifled, like the French MO-120-RT, which increases accuracy but requires a complex loading system. The Soviet 2B9 Vasilek is a unique automatic mortar that can fire in both direct and indirect modes.¹

Mortars are used for close support, smoke screening, and illumination. They are often assigned to infantry battalions, with fire direction centers coordinating fire missions. The high angle of fire allows engagement of targets in defilade, such as behind hills or buildings, which direct-fire weapons cannot reach.

In urban warfare, mortars are valuable for suppressing enemy positions on rooftops or in courtyards. However, their use in populated areas raises concerns about collateral damage, leading to the development of precision-guided mortar rounds. Mortars also serve on naval vessels for close-range defense and on patrol boats.

One obscure fact is that the U.S. Army experimented with a 4.2-inch (107 mm) chemical mortar during World War II, designed to deliver smoke and chemical agents. Another is the existence of the 'spigot mortar', such as the British PIAT, which used a spring-loaded spigot to launch a bomb, avoiding the recoil of a conventional barrel.

The smallest mortars, like the 50 mm Japanese Type 89 grenade discharger (knee mortar), were lightweight and could be fired by one soldier. In contrast, the largest mortars, such as the Soviet 240 mm M-240, are towed and fire shells weighing over 130 kg. Mortars have also been used in space: the Soviet Union's Luna program used a mortar to deliver scientific instruments to the lunar surface in 1959.¹

Defilade

A position protected from enemy fire by natural or artificial obstacles, such as a hill or wall.

High-explosive (HE)

A shell filled with explosive material designed to detonate on impact.

Smoothbore

A barrel without rifling, which imparts no spin to the projectile.

Spigot mortar

A type of mortar that uses a rod (spigot) to launch a projectile, rather than a conventional barrel.