M109 howitzer


The M109, widely known as the Paladin, is an American 155 mm turreted self-propelled howitzer, first introduced in the early 1960s to replace the M44 and M52. It has been upgraded a number of times, most recently to the M109A7. The M109 family is the most common Western indirect-fire support weapon of maneuver brigades of armored and mechanized infantry divisions. It has a crew of four: the section chief/commander, the driver, the gunner, and the ammunition handler/loader.
The British Army replaced its M109s with the AS-90. Several European armed forces have or are currently replacing older M109s with the German PzH 2000. Upgrades to the M109 were introduced by the U.S. and by Switzerland. With the cancellation of the U.S. Crusader, non-line-of-sight cannon and M1299, the M109A6 will likely remain the principal self-propelled howitzer for the U.S. until a replacement enters service.

Operational history

The M109 was the medium variant of a U.S. program to adopt a common chassis for its self-propelled artillery units. The light version, the M108 Howitzer, was phased out during the Vietnam War, but many were rebuilt as M109s.
The M109 saw its combat debut in Vietnam. Around 200 vehicles were deployed in 1966, but the entire fleet suffered a mechanical malfunction within a year of operation. The U.S. dispatched engineers and mechanics, but all M109s were recalled back to the U.S. in 1967 after failing to repair in the field. The howitzer underwent upgrades afterward, which resulted in the M109A1.
Israel used the M109 against Egypt in the 1973 Yom Kippur War and in the 1982 and 2006 Lebanon Wars. Iran used the M109 in the Iran–Iraq War in the 1980s. The M109 saw service with the British, U.S. Army, Egyptian and Saudi Arabian Armies in the 1991 Gulf War. The M109 also saw service with the U.S. Army in the Iraq War from 2003 to 2011.
File:DS1991.jpg|thumb|M109 howitzers belonging to 4th Battalion of the 3rd Field Artillery Regiment, 2nd Armored Division conducts artillery strikes on Iraqi positions during the Gulf War
Upgrades to the cannon, ammunition, fire control, survivability, and other electronics systems over the design's lifespan have expanded the system's capabilities, including tactical nuclear projectiles, guided projectiles, rocket-assisted projectiles, family of scatterable mines, and cluster munitions.
In August 2015, South Korean K55A1s fired rounds behind the Military Demarcation Line as a warning after several North Korean provocations.
During the Russian invasion of Ukraine, Ukraine has used M109 howitzers donated by Western countries. According to video and photographic evidence compiled by the open-source intelligence website Oryx, as of 24 September 2024, at least 70 units of different [|variants] had been lost.

Design

The M109 was developed by the Ground System Division of United Defense LP, now BAE Systems Platforms & Services.

Armament

The M109 was powered by the 8V71T, a 8-cylinder water-cooled diesel engine, produced by the Detroit Diesel Engine Division of General Motors Corporation. The 8V71T is a turbocharged version of the 8V71 commercial truck engine. It was rated 390 hp at 2300 rpm and was used in the M107, M108, M110, and M578 series as well.

Variants

M109

First produced in 1963. It had a 155 mm M126 cannon in an M127 mount, and carried 28 rounds of 155 mm ammunition. It was also armed with a.50cal M2HB machine gun with 500 rounds of ammunition. Easily identified by its short barrel and a double baffle muzzle brake with a large fume extractor just behind it. Maximum range of 14,600 meters.

M109G

The West German army M109s were designated as the M109G, and featured a breechblock system developed by Rheinmetall extending the effective range to or according to some sources, a new fire control system, and three smoke dischargers mounted on either side of the turret as well.
In December 1966, the United States and Norway signed an agreement related to the co-production of the M109G.

M109A1

Fielded in 1973, this modification replaced the M126 cannon with a 39 caliber M185, featuring a longer barrel while increasing maximum range to 18,100 meters.

M109A1B

The M109 rebuilt to M109A1 standard.

M109 66/74

The M109 66/74 is a Swiss upgraded M109 to M109A1B standard.
Switzerland purchased 146 M109 under the armament program 1968, and introduction of the howitzer started in 1971. All vehicles received upgrade to M109A1B standard and were delivered from May 1977 to February 1979.

M109A2

Incorporated 27 Reliability, Availability, and Maintainability mid-life improvements. Most notably, the long barreled 155 mm M185 Cannon in the new M178 gun mount, ballistic protection for the panoramic telescope, counterbalanced travel lock, and the ability to mount the M140 bore sight alignment device. Stowage of 155 mm rounds increased from 28 to 36 rounds;.50cal ammunition remained at 500 rounds. Fielded in 1979.
During M109A2 production, a slightly simplified version was also produced for export. This had minor internal changes and deleted the hull flotation feature. These were designated M109A1B.

K55

The K55 is a South Korean license produced variant of the M109A2. In the 1960s, the South Korean Army received M107 and M110 from the United States. However, the number of these self-propelled guns was insufficient to counter rapidly-growing North Korean artillery capabilities. In the 1970s, South Korea began mass-producing towed howitzers locally, but intelligence reports of North Korean 170 mm self-propelled artillery forced South Korea to look for a new self-propelled artillery system.
In December 1983, the ministers of defense of the United States and South Korea signed a memorandum of understanding to co-produce M109A2 in South Korea using American technical data. The United States delivered two completed M109A2s to South Korea for operational review, and the Agency for Defense Development began to translate the data package and created field and maintenance manuals for soldiers. South Korea wanted to produce every part of the vehicle domestically; however, due to the amendment bill by Rep. Samuel S. Stratton of New York, which established a limit for foreign military technology cooperation, the turret and the M185 cannon from Watervliet Arsenal were imported from the United States.
Compared to the M109A2, besides 63 percent of parts being produced locally, K55 has a driver's night periscope and light exposure minimization device to enhance night-time operations as well as additional radio systems. The vehicle has a nuclear, biological and chemical protection system and halon fire extinguishers. A total of 1,180 K55s were produced between 1985 and 1996. The vehicle's name was changed from KM109A2 to K55, originally a code name from the Samsung factory.
In November 1990, the United States and South Korea signed an agreement to allow South Korea to supply M109 parts to third parties. In May 1997, during the Security Cooperation Committee held in Washington D.C., South Korea requested that the United States revise the MOU to export complete K55s, originally intended for domestic use only. South Korea was expecting to export 72 K55s and four ammunition support vehicles to Brazil for $160 million over Belgium's offer, but the United States Department of Defense declined the request to avoid an arms race in the region.
In May 1998, the South Korean military began operating a K55 simulator to boost artillery operator training. The simulator took a year and a billion KRW budget to develop. It is expected to save 150 million KRW per year per device.

M109A3

M109A1s rebuilt to M109A2 standard, also fielded in 1979. Some A3s feature three contact arm assemblies, while all A2s have five.

M109A3B

M109A1B rebuilt to M109A2 standard.

M109A3G

In 1983, the German Army purchased 586 conversion kits from the FMS Corporation to convert its fleet of M109Gs to the M109A3G standard. This upgraded variant uses a new gun barrel developed by Rheinmetall, giving an extended range of. It also features a new fire-control system, and three forward firing 76 mm smoke grenade launchers on either side of the turret.

M109A3GN

Between 1969 and 1971 Norway acquired 126 M109Gs from West Germany. They were then upgraded to the M109A3GN configuration during the latter half of the 1980s.

M109L

M109A4

Soon after the adoption of A2/A3 versions, the Division Weapon Support System study was initiated in 1980, which by the end of the decade resulted in the development of several modernization packages. The most modest one was the Howitzer Extended Life Program update originally designated as M1903A3E1 and later adopted as M109A4, initially scheduled for 1985-1987 but actually fielded in 1989 in the Reserve Component of the US Army.
This modernization program fitted M109A2s and M109A3s with Nuclear, Biological, and Chemical / Reliability, Availability, and Maintainability improvements, including air purifiers, heaters, and Mission Oriented Protective Posture gear.
The traversing mechanism's clutch was changed to be hydraulic, and added a manual override. The M109A4 also gained a second hydraulic filter and more reliable engine starting equipment which greatly improved the ability to start the vehicle in an emergency.
Ammunition stowage remained the same as in previous models.

M109A5

This modification was also designed for the US Army Reserve, originally planned as an update for all M109A4s under the second phase of the Reserve Component Modified Armament System to bring the range up to the version adopted as M109A6. It was fielded in 1991 in much smaller numbers than originally devised due to the end of the Cold War.
It replaced the 155 mm M185 cannon in an M178 mount with a 39-caliber 155 mm M284 cannon in an M182 mount developed for the M109A3E2, giving the A5 a maximum range of 22,000 meters with unassisted projectiles and 30,000 meters with rocket-assisted projectile rounds. The vehicle can carry 36 complete rounds of ammunition and has a 440 hp engine instead of the standard 405 hp engine.