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Smart Bombs: Military, Defense and National Security

The Army’s M109 Howitzer Is the ‘Big’ Gun Russia and China Fear Most


The American M109 155 mm turreted self-propelled howitzer has formed a core component of the American military’s artillery force since its introduction in the 1960s, and has featured for a number of other militaries around the world and ranks as one of the most common Western indirect-fire weapon systems. The M109 has been upgraded several times over the years and has taken part in several international conflicts during its operational lifetime. The M109 remains in service with the United States military, and it will likely continue to do so for several years before the system is eventually replaced with a still-in-development successor in the form of the M1299.

M109, A History 

Early development of the M109 dates back to 1952 to a United States Army requirement for the development of a more mobile, mechanized artillery system capable of keeping up with armored and mechanized units. The M109 was envisioned as providing the Army with a more mobile artillery weapon than its towed M114 howitzers and a more capable system than the M44 self-propelled howitzer. The M109 was developed alongside the lighter M108 105 mm artillery system, which was ultimately canceled before most M108s were converted into M109s. The first M109 prototypes were completed in 1959, and the system entered into production in 1962.

The M109 was armed with the M126 155 mm howitzer cannon, and was equipped with 28 rounds of ammunition. The system had a maximum range of roughly 14,600 meters when firing standard High Explosive rounds and a range of approximately 20,000 meters when using rocket-assisted projectiles. The M109 was capable of firing as many as four rounds per minute, but had a sustained fire rate of two rounds per minute. The M109 was also armed with a secondary M2HB heavy machine gun that was mounted on the commander’s cupola on top of the turret.

Early M109s were protected by up to 32 millimeters of armor, enough to protect the vehicle from small arms fire and grenades but not enough to protect it from heavier anti-vehicle weaponry. The M109 is powered by a 450 horsepower Detroit Diesel 8V71T engine that gives the M109 a maximum speed of 65 kilometers an hour and a maximum range of 390 kilometers. The M109 can also be outfitted with a floatation kit for fording water obstacles and is propelled by tracks while on the water for a maximum amphibious speed of 6.5 kilometers per hour.

A crew of six operates the M109, including a commander, two gunners, two loaders, and a driver, and the system has often been accompanied by the M992 armored supply vehicle that is based on the same tracked chassis as the M109.

A host of variants of the M109 have been developed over the years. The first of these variants – the M109A1 – was first introduced in 1970 and was first delivered in 1973. Improvements included a new main gun in the form of the M185 that allowed for improved range and use of laser-guided rounds, and also included a more efficient muzzle brake, improved loading assist system, and an upgraded suspension.

Production of the M109A2, which featured more space for ammunition and an improved gun mount, began in 1978, while the M109A3 was the designation given to M109A1s upgraded to M109A2 standard. The M109A4 provided nuclear, biological, and chemical (NBC) protection, while the M109A5 introduced the new M284 cannon that offered improved range (an M109A5+ version, with an improved fire control system, was also introduced).

M109-A6 Paladin Self-Propelled Howitzer

U.S. Army Sgt. Manuel Sarabia, a native of San Diego, assigned to A Battery, 4th Battalion, 27th Field Artillery, Division Artillery (DIVARTY), 1st Armored Division as a crew chief in a M109-A6 Paladin Self-Propelled Howitzer, listens to firing commands over the radio during the first day of DART (Division Artillery Readiness Test) at Dona Ana firing range just outside Fort Bliss, Texas, Dec. 7, 2015. DART is a new, three-day exercise that will determine the readiness of DIVARTY FA units through live-fire exercises, react to contact, improvised explosive device (IED) defense and casualty and vehicle evacuation. (U.S. Army Photo by Sgt. James Avery, 16th Mobile Public Affairs Detachment)

The M109A6 Paladin, introduced in 1991, represented the first major improvements for the M109 platform as a whole. Major upgrades found on the M109A6 Paladin include the addition of more armor, enhanced sensors, and upgraded communications systems, along with a generally improved overall design.

The most recent addition to the M109 series of howitzers is the M109A7, which has also been given the Paladin designation. The newest M109 howitzer system includes a number of enhancements such as a new chassis and improved engines, suspension, transmission, and steering systems. Many of these parts are also found on the Army’s Bradley Infantry Fighting Vehicles, which will reduce maintenance costs and improve interoperability. In addition, new Paladins will feature on-board digital fire control systems and more sophisticated navigation systems that will provide better firing data.

U.S. Army Birthday

U.S. Army Soldiers assigned to Alpha Battery, 3rd Battalion, 29th Field Artillery Regiment, 4th Infantry Division, fire a M109A6 Paladin in support of the joint training exercise Eager Lion ’19 at Training Area 1, Jordan, Aug. 27, 2019. Eager Lion is an annual, multinational training event in its ninth iteration which enables partnered nations to strengthen military relationships and exchange expertise. (U.S. Army photo by Spc. Angel Ruszkiewicz)

Written By

Eli Fuhrman is an Assistant Researcher in Korean Studies at the Center for the National Interest and a recent graduate of Georgetown University’s Security Studies Program, where he focusedd on East Asian security issues and U.S. foreign and defense policy in the region.