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Howitzers, both towed and self-propelled, have been mainstays of both the Russians who invaded Ukraine on Feb. 24, 2022, and the Ukrainians who have so skillfully resisted them. Among the most awaited Western types that just entered the Ukrainian arsenal in late May 2022 is a lethal American self-propelled howitzer that has been in military service for almost 60 years.  

History of the M109 Howitzer 

The M109 self-propelled howitzer was conceived in 1960 by the Ground System Division of United Defense LP (now part of BAE Systems Land and Armaments) as a replacement for the M44 using a chassis and other components common to other U.S. Army vehicles. Accepted in November 1962 and entering operational service in Vietnam, where its 360-degree traversing ability made it an instant asset at fire bases, the air-transportable M109 mounted an M126 23-caliber, 155 mm howitzer within an armored turret, as well as a flexible .50-caliber M2HB machine gun. A lighter version, the M108 with a 105 mm howitzer, entered service at Pleiku on June 17, 1966, but was abandoned in 1975, with many being adapted to carry the M109’s 155 mm gun.  

In 1973, the M109A1 entered production, featuring a 39-caliber M189 cannon with a longer tube and more slender muzzle brake, which increased range from 15,967 to 19,794 yards. A succession of upgrades in armament and technology followed.  

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M109 Stats 

The M109A2 was powered by a 405-hp Detroit Diesel 8V71T Model 7083-7396 two-stroke, eight-cylinder diesel, with an Allison XTG 411-A2 cross-drive transmission with four forward and two reverse speeds. Its length was 29 feet, 11 inches, its width 10 feet, 4 inches, its height 10 feet, 10 inches and its combat weight 27.5 tons.  

Its armament comprised one M185 39 caliber, 155 mm howitzer with 36 rounds of ammunition, one flexible turret-mounted M2 .50-caliber machine gun. The six-man crew could quick-fire 4 rounds per minute for three minutes or sustain one round per minute. The gun’s maximum effective range was 11.2 miles, but a rocket extended round could stretch that to 14.6 miles. The self-propelled gun had a road speed of 35 mph, with a cross-country speed of 20 mph. Its maximum range was 217 miles 

The M109’s usefulness got a new lease on life with advances in electronics. The M109A6 Paladin, which entered production in 1994, introduced an advanced fire control system that allowed firing 30 seconds after stopping, greatly assisting in avoiding counterbattery fire. It also introduced more automation, an internal navigation system and an encrypted digital communication system that protects its information from outside interference by computer-controlled frequency hopping.  

The M109 Today 

The last of a 950-vehicle order was completed in 1999. A further upgrade of the basic design, the M109A7, was approved for production in 2013. Although having the same engine, chassis, transmission and tracks as the Bradley Fighting Vehicle, providing commonality in maintenance into the future, the 39-ton M109A7 is faster and more maneuverable than the BFV. 

Used by armies all over the world, M109s have seen combat in every American war since Vietnam, as well as the 1973 Holy Day War, the 1982 and 2006 Israeli interventions in Lebanon and the 1980-1988 Iran-Iraq War.  

In the spring of 2022, as a gesture of support from the North Atlantic Treaty Organization, the United Kingdom acquired and repaired more than 20 M109s from a private firm in Belgium, repaired them and sent them to Ukraine to oppose the Russians.  In May, Ukrainian crews received training from U.S. Army and Norwegian artillerymen for 22 M109A3GN guns, which arrived at the front in June. This Norwegian model of M109 was modernized in 1980s and has a barrel length of 39 calibers instead of 23.  

As more NATO donations come in, the M109s are expected to make their mark as the latest Russian nemeses in a remarkably long career that has yet to see any sign of them outliving their usefulness. 

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