Field artillery has been called “The King of Battle.” And for good reason. Great generals throughout history have lauded the power and necessity of artillery in battle. Artillery wins battles and, therefore, could win wars. Mortars are basically the light artillery of the infantry. The US military uses a variety of mortar calibers for infantry support.

The 81mm mortar is a portable, mobile, medium mortar at the infantry’s disposal.

Mortars are indirect-fire weapon systems. The term “indirect fire” means firing at an enemy without having a direct line of sight. A rifle or a tank, for example, are direct-fire weapons. You see the enemy, you aim, and fire that munition directly at him. Mortars are indirect-fire weapons that rely on mathematical calculations to fire a munition at a high angle, which then arcs down onto the intended target.

The Infantry Mortar Platoon

In the US Army and the US Marine Corps, the 81mm mortar is a battalion asset. This means that each infantry battalion has a mortar platoon providing indirect fire support for the other infantry companies in the battalion. This mortar platoon has four squads of infantrymen, plus a fire direction section (squad), that makes the fire control calculations. Each mortar platoon has four 81mm medium mortars at its disposal — one for each squad. They also have four M120 heavy mortars, but typically, each squad only operates one mortar at a time.

Mortar systems can provide three different types of “fires” — types of rounds and engagement — for the infantry units they are supporting.

US Infantry mortar platoon composition
Unit composition of the infantry mortar platoon taken from ATP 3-21.20. Unclassified.

Firstly, high explosive rounds (HE) are used to suppress or destroy enemy infantry, weapons, and equipment. They are also used to deny enemy movement and mobility in certain areas.

Obscuration rounds, or smoke rounds, create a smokescreen within the target area. This smokescreen can either help conceal the movements and locations of friendly units or obscure the vision of enemy units.

Thirdly, illumination rounds. These are fired directly into the sky at night over a target area. Once the shell explodes, a bright flare ignites and offers light and visibility of the area below. These can also include infrared (IR) illumination, not visible to the naked eye without the use of other optic systems.