Mortar (weapon) - Function

Function

A mortar is relatively simple and easy to operate. A modern mortar consists of a tube into which assistant gunners drop a purpose-designed bomb. The tube is generally set at between 45 and 85 degrees angle to the ground, with the higher angle giving shorter firing distances. The bomb has no cartridge case; the propellant is attached to the bomb's fins. When it reaches the base of the tube it hits a firing pin, which detonates the propellant and fires the projectile. Some larger caliber mortars have a string-operated firing pin.

These attributes contrast with the mortar's larger siblings, howitzers and field guns, that fire shells at higher velocities, longer ranges, flatter arcs, and sometimes using direct fire. These weapons are also breech-loaded while mortars are muzzle-loaded.

From the 18th to the early 20th century very heavy, relatively immobile siege mortars were used, of up to one metre calibre, often made of cast iron and with outside barrel diameter many times that of the bore diameter. Smaller and more portable designs were introduced during the First World War, primarily for trench warfare, which took place at relatively close ranges. Mortars continue to be in use to the present day.

Light and medium mortars are portable, and usually used by infantry units. The chief advantage a mortar section has over an artillery battery is the flexibility of small numbers, mobility and the ability to engage targets in the defilade with plunging fires. Mortars are able to fire from the protection of a trench or defilade. In these aspects, the mortar is an excellent infantry support weapon, as it can be transported over any terrain and is not burdened by the logistical support needed for artillery.

Heavy mortars are typically between 120- and 300-mm calibre. These weapons are usually towed or vehicle-mounted, sometimes breech-loaded, and normally employed by infantry units attached to battalion through division level. Even at this size, mortars are simpler and less expensive than comparable howitzers or field guns.

A mortar can be carried by one or more people (larger mortars can usually be broken down into components), or transported in a vehicle. An infantry mortar can usually also be mounted and fired from a mortar-carrier, a purpose-built or modified armoured vehicle with a large roof-hatch. A mortar can also be a launcher for fireworks, a hand-held or vehicle-mounted projector for smoke shells or flares, or a large grenade launcher. Heavy mortars can be mounted on a towed carriage, or permanently vehicle-mounted as a self-propelled mortar. Twin-barrelled self-loading mortars—such as the Patria AMOS PT1—are the latest evolution of these heavy mortars and are mounted on platforms such as armoured personnel carriers, tank chassis, and coastal patrol boats.