The M198 155mm howitzer is a towed, medium-sized artillery weapon that was developed for service in the United States Marine Corps and Army. It was commissioned as a replacement for the M114 155mm howitzer that was used during the era of World War II. The M198 was designed and prototyped in 1969 at the Rock Island Arsenal. Firing tests began in 1970, and the weapon went into full production in 1978. Since it entered service in 1979, 1,600 units have been produced and put into operation. This weapon has been deployed in many separate army- and corps-level field artillery units, as well as various battalions of airborne and light divisions. It also provides support for all of the Marine Air-Ground Task Force organizations.

Weighing less than 16,000 pounds, the M198 may be dropped by parachute or transported by a CH-53E Super Stallion or CH-47 Chinook. This howitzer is towed and transported tail-first, however the gun tube may be rotated over its trail legs to reduce its length. Instead of being anchored to the ground, the weapon is then lowered onto its baseplate when firing for rapid emplacement. The breach is operated manually with a screw-type mechanism that rests in a low ergonomic position. The M198’s effective range is 18,100 meters when firing standard projectiles, and increases to up to 30,000 meters when firing guided ammunition and rocket-assisted projectiles; with modification, the firing 52-caliber ammunition may surpass 40,000 meters. This weapon system requires a crew of 9 and fires at a maximum rate of four rounds per minute.

The M198 fires non-fixed ammunition and may be loaded with a wide variety of projectiles and propellants, including:

• High Explosives (He) – Composition B material that is packed into a thick, internally scored shell. This causes a large blast and sends razor-sharp fragments at extreme velocities (5,000-6,000 meters per second).

• Rocket Assisted Projectiles (RAP) – A rocket-assisted high explosive that adds to the maximum range of the normal high explosive. Max range is around 18.7 miles.

• White Phosphorus (WP) – A base-ejecting projectile that may come in two versions: standard or felt-wedge. The smoke created by this projectile is used to start fire, burn targets, or create smoke when concealing movements.

• Illumination – These projectiles are base-ejecting rounds that deploy a bright parachute flare to illuminate an area of approximately 1 grid square (or 1,000,000 square meters.)

• Dual-Purpose Improved Conventional Munition (DPICM) – A base-ejecting projectile that drops 88 bomblets above its target.

• Area Denial Artillery Munition System (ADAMS) – Artillery round that releases anti-personnel mines.

• Remote Anti Armor Mine System (RAAMS) – Artillery rounds used to release anti-armor mines, usually along with ADAMs rounds to prevent anti-tank mines from being removed.

• Copperhead – Artillery launched guided high-explosive munition that is used for precise targeting.

• Sense and Destroy ARMor (SADARM) – An experimental munition fired in the general direction of the enemy vehicle.

• W48 Nuclear Shell – An artillery shell that has a 155mm caliber and explosive yield of only 72tons – making it one of the world’s smallest nuclear weapons.