The M109 is an American-made self-propelled 155 mm howitzer, first introduced in the early 1960s. It was upgraded a number of times to today's M109A6 Paladin. The M109 family is the most common Western indirect-fire support weapon of maneuver brigades of armored and mechanized infantry divisions.
The M109 has a crew of six: the section chief, the driver, the gunner, the assistant gunner and two ammunition handlers. The gunner aims the cannon left or right (deflection), the assistant gunner aims the cannon up and down (quadrant). The M109A6 Paladin needs only a crew of four: the commander, driver, gunner and ammunition 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, which outperforms the M109 in many aspects. Upgrades to the M109 were introduced by the U.S. (see variants below) and by Switzerland (KAWEST). With the cancellation of the U.S. Crusader, the Paladin remains the principal self-propelled howitzer for the U.S. for the foreseeable future.
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. Israel used the M109 against Egypt in the 1973 Yom Kippur War and in the 1982 Lebanon War and 2006 Lebanon War. Iran used the M109 in the Iran Iraq War, in the 1980s. The M109 saw service with the British Army, the Egyptian Army and Saudi Arabian Army in the 1991 Gulf War. The M109 also saw service with the U.S. Army in the Gulf War, as well as in the Iraq War from 2003 to present.
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, Cannon Launched Guided Projectiles (CLGP or Copperhead), Rocket Assisted Projectile (RAP), FAmily of SCAtterable Mines (FASCAM), and improved conventional munitions (the Dual-Purpose Improved Conventional Munition, DPICM).
The developing BCT Ground Combat Vehicle Program will likely replace the M109 as well as many other US army vehicles.
Open breech of M109A5 howitzer.
First produced in 1963, with 155 mm M126 gun in the M127 Howitzer Mount, 28 rounds of 155 mm were carried. Also armed with a .50cal M2HB machine gun mounted, and 500 rounds of .50cal ammunition.
M109A1 and M109A1B
Replaced M126 with longer barreled M126A1 gun for greater effective range. Same M127 mount and ammunition amounts carried. A more recent model, intended for export incorporated more recent improvements into a new production M109A1. These were designated M109A1B.
Incorporated 27 Reliability, Availability, and Maintainability (RAM) mid-life improvements. Most notably, the long barreled 155 mm M185 cannon in the M178 gun mount, ballistic protection for the panoramic telescope, counterbalanced travel lock, and the ability to mount the M140 alignment device. Stowage increased from 28 rounds of 155 mm, to 36 rounds, .50cal ammunition amount remain 500 rounds.
M109A3 and M109A3B
M109A1s and M109A1Bs rebuilt to M109A2 standard respectively. Some A3s feature three contact arm assemblies while all A2s have five.
M109A2s and M109A3s improved with Nuclear, Biological, and Chemical / Reliability, Availability, and Maintainability (NBC/RAM) improvements, including air purifiers, heaters, and Mission Oriented Protective Posture (MOPP) gear.
The traversing mechanism's clutch is hydraulic, as compared to the electric mechanism on previous M109s, and features a manual override in the event of an electrical failure. The A4 also adds an additional hydraulic filter, for a total of two. Also included is an improvement to the engine starting equipment, greatly improving the ability to start in an emergency.
Ammunition amounts remain the same as two previous models.
Replaces 155 mm M185 cannon in M178 mount with 39-caliber 155 mm M284 cannon in the M182 mount, giving the A5 a maximum range of 23,500 meters with unassisted projectiles and 30,000 meters with Rocket Assisted Projectiles (RAP Rounds). The vehicle can carry 36 complete rounds of ammunition, has a 440 hp engine instead of the standard 405 hp engine. M109A5 under repair.
Various manufacturers have upgraded the fire control and other components of the M109A5.
An M109A6 howitzer from Alpha Battery, 3rd Battalion, 82nd Field Artillery, 2nd Brigade Combat Team, 1st Cavalry Division, sends a round down range during combat operations in Fallujah, Iraq.
M109A6 "Paladin" firing at night.
Overall product improvement in the areas of survivability, RAM, and armament. This includes increased armor, redesigned (safer) internal stowage arrangement for ammunition and equipment, engine and suspension upgrades, and product improvement of the M284 cannon and M182A1 mount. The greatest difference is the integration of an inertial navigation system, sensors detecting the weapons' lay, automation, and an encrypted digital communication system which utilizes computer controlled frequency hopping to avoid enemy electronic warfare and allow the howitzer to send grid location and altitude to the battery fire direction center (FDC). The battery FDCs in turn coordinate fires through a battalion or higher FDC. This allows the Paladin to halt from the move and fire within 30 seconds with accuracy equivalent to the previous models when properly emplaced, laid, and safed a process that required several minutes under the best of circumstances. Tactically, this improves the systems survivability by allowing the battery to operate dispersed by pairs across the countryside and allowing the howitzer to quickly displace between salvos, or if attacked by indirect fire, aircraft, or ground forces.
The performance of the M109A6 is comparable to that of the first self-propelled artillery over the preceding towed artillery, since the howitzers are not fixed, but may move with the combat forces. They need stop only when a target is identified. After firing on a target, the Paladin is immediately able to resume movement.
Ammunition stowage is increased from 36 to 39 155 mm rounds.
This Swiss improved version produced by Ruag incorporates a new Swiss-designed L47 155 mm gun with an increased firing range of up to 36 km. The L47 155 mm gun is derived from the Swiss Bison fortress gun's inertial navigation system coupled with a new gun-laying system and more ammunition storage. The KAWEST (lit. Kampfwertsteigerung = upgrade of combat capabilities) requires only 6 crew members instead of 8, and is able to fire 3-round bursts within 15 seconds or maintain a constant firing rate of over one round per minute. Technical modifications: Increased firing range of up to 27 km, increased rate of fire (burst of 3 rounds in 15 sec.), increased ammunition autonomy (40 rounds, 64 charges). New electrical system increases reliability (better than Mil STD 1245A, higher operational readiness, increased mean time between failures, fault-finding diagnostics with test equipment.) Integrated inertial navigation and positioning system, increased mobility (gears, engine), day and night operations capabilities, effective fire suppression system installed, NEMP and EMP protection. Camouflage: paint and netting. Upgraded Swiss PzHb (Panzerhaubitze) 79 and 88 (M109A1) are known as respectively PzHb 79/95 and PzHb 88/95.
Jointly developed by the Dutch firm RDM and the German firm Rheinmetall, the M109L52 was first revealed in 2002. The main improvement was replacing the M126 series gun with the longer 52-caliber cannon from the PzH 2000, thus the MTLS ammunition of the PzH 2000 can be used. In addition, improvements to the loading system were made. This resulted in an increase of the rate of fire to 9 10 rds/min from the original 3 rds/min, and this high rate of fire can be sustained for up to 2 minutes. A total of 35 rounds can be carried and trials have revealed that the M109L52 is 90% as effective as the PzH 2000, while the unit price of the M109L52 is only 15% to 30% of the PzH 2000. The M109L52 provides an attractive alternative to customers with financial constraints that prevent them from replacing older M109s with the PzH 2000 on a one-to-one basis.
K55/K55A1 are South Korean variants of the M109, originally based on M109A2 with additional domestic augmentations, license-produced by Samsung Techwin. they are fitted with NBC protection, automatic fire extinguishing system, and a modified ammunition reception module for K56 automatic ammunition resupply vehicle. The Performance Improvement Program variant, K55A1, is a complete domestic overhaul of the K55 which is further augmented by Samsung Thales with modern digital ballistic computers, multifunctional data display and controllers, GPS navigation and target acquisition system, wireless datalink equipment, and upgraded fire control storage battery and power supply unit, to closely match the US military's modernization of the Paladin into next-generation standard. Many improved technologies of the South Korean K9 Thunder were retrofitted on the K55A1. 1,040 to 1,180 howitzers of these variants were produced.
The replacement for the M109A6 in U.S. service is the M109 Paladin Integrated Management (PIM). PIM shares common components with the Bradley Fighting Vehicle such as the engine, transmission, and tracks. This creates commonality with other systems and maximizes costs-savings in production. The PIM's on-board power systems harness technologies originally developed for the Non-Line-of-Sight Cannon. The PIM can sustain a one round per-minute rate of fire and a maximum rate of fire of four rounds per-minute.
Prototypes of the vehicle are undergoing government testing in preparation for an low-rate initial production decision. The testing includes reliability, availability and maintainability mission testing as well as ballistic hull and turret testing. PIM is slated to begin low-rate initial production by 2013. The U.S. Army plans on procuring a fleet of 580 PIM enabled sets of howitzers and ammunition support vehicles. PIM is designed to accommodate networking technologies as they become ready.
The Field Artillery Ammunition Supply Vehicle (FAASV) is built on the chassis of the M109-series. It is also colloquially referred to as a "CAT" (referring to its nomenclature, CAT: Carrier, Ammunition, Tracked). It replaces the M548 supply vehicle. Unlike the M548 it is armored. This ammunition vehicle has no turret but has a taller superstructure to store 93 rounds and an equivalent number of powders and primers. There is a maximum of 90 conventional rounds, 45 each in two racks, and 3 M712 Copperhead rounds. Until recently much of the remaining internal crew space is taken up by a hydraulically powered conveyor system designed to allow the quick uploading of rounds or transfer of rounds to the M109-series howitzer. Most early models had an additional mechanism called an X-Y Conveyor to lift the rounds into the honeycomb-like storage racks in the front of the superstructure. A ceiling plate above the two racks can be unbolted and opened to allow the racks to be winched out of the vehicle. This vehicle is fitted with a Halon fire suppression system and a weapons mount similar to that on the M109 turret, usually mounting a Mk 19 grenade launcher for local defense against infantry and light armored vehicles. The latest models have a mounting point for two secure radios.
The hydraulic conveyor system is removed by crews as it is slower than moving the rounds by hand. Recently the army has removed the conveyor system and changed the two horizontal opening doors to two vertical doors opening from the center to provide protection to the crew during transfers.
The vehicle also contains a 2-stroke diesel powered auxiliary power unit that can power all non-automotive energy requirements on the Field Artillery Ammunition Supply Vehicle and on the howitzer when a slave cable is used to connect the two. This reduces fuel consumption when mobility is not required.
The US Army uses the Fire Support Combined Arms Tactical Trainer (FSCATT) in two versions for initial and sustainment training of the M109A6 and M109A5. The system uses an actual surplus turret and a simulated ammunition system.
The Swiss Army uses a highly advanced KAWEST trainer from Van Halteren Metaal of the Netherlands.
The Dutch, Belgian, Thai, and Israeli Armies have various configurations of the Van Halteren Metaal LARIT M109 trainer.
M109 operators 2011 (former operators in red) M109 self-propelled howitzer of the Egyptian Army during Operation Bright Star.
- : 48 (24 from Switzerland, upgraded to M-109 KAWEST) 12 A3 and 12 A5 Upgrade to similar Paladin configuration
- : 17
- : 51 A1B
- : 390
- : 5 A1B
- : 44 M109A1 (ex-swiss)
- : 15 A0
- : 12
- : 224 (upgraded to M109 KAWEST)
- : 40 (from Switzerland)
A Spanish Marines M109A2.
- : 127 A2 (of which 64 upgraded to A4BE; all now decommissioned)
- : 40 A3 (former Belgian) Brazilian Army
- : 12 (upgraded to M109 A3DK)
- : 570 A3GE A1/A2 (phased out by 1 July 2007, replaced by the PzH 2000)
- : 84 A2, 50 A3GEA1, 223 A3GEA2 
- : 400 A2
- : 221 M109L (with an Italian made 155 mm/39 calibre barrel)
- : 356 A2/A2-90 (121 M109A2-90 purchased from Netherlands)
- : 43 M109A2 (Ex-Belgium) and 40 M109A3.
- : 126 A2/90 phased out, largely replaced by the PzH 2000.
- : 56 A3G (14 upgraded to A3GN, and then nine of these upgraded to A3GNM to suit the winter climate)
- : 250 A2
- : 6 A2 since 1981 (Portuguese Army). Currently retired from active-service and being used only in training duties.
- : 60 A2s are currently being upgraded to A5s (2010)
- : 6 (Spanish Marines)
- : 19-20 A2
- : 80 A2/A5
- : 225, That'll update to A6 spec.
- : 64 A4BE (all now decommissioned and 40 A3BE sold to Brazil)
- : 76 A4B+ Phased out from the Canadian Forces since 2005, they were used between 1967 to 2005. All vehicle had been modernized to the M109A4B+ SPH standard in 1980s. They were primary used by the 4 Canadian Mechanized Brigade Group in Germany.
- : 300 A4BE
Moroccan M109A5 howitzer in March 2012.
- : 20
- : 201
- : 36
- : 24
- : 600
- : 115
- : 18 since 2002 (Portuguese Army). 14 of these vehicles were M109A2/A3 upgraded to A5 variant. This variant replaced the previous 6 M109A2 operated by the Portuguese Army.
- : 20
- : 12
- : 96 (Spanish Army)
- : 60
ar: 109 de:M109 (Panzerhaubitze) et:M109 es:Ob s autopropulsado M109 fr:M108/M109 ko:M109 it:M109 (semovente) he: M-109 hu:M109 ( nj r tarack) ms:Howitzer M109 nl:M109-houwitser ja:M109 155mm no:M109 pl:M109 SPH pt:M109 howitzer ru:M109 ( ) th: 109 zh:M109