The 105mm Howitzer

Whenever someone mentions artillery, the mental image that springs into my mind is a crew of redlegs from World War II or maybe Vietnam loading and firing a 105mm howitzer.

The primary light artillery piece of the Army in World War I was the 75mm howitzer  M1897 GUN (thanks, Craig) , based on a French design. President Truman commanded a battery of them as a Captain in the war.

But the Army wasn’t very happy with the French 75. It was light and handy, but the round wasn’t very impressive. It lacked penetration against fortification, and the range was rather anemic. Something better was wanted.

The Army used some of its tiny interwar budget to develop a 105mm gun in the early 1920s. It was generally pleased with the results, but there was simply no money to replace the 75mm guns in the inventory. More importantly, there was no money to replace the vast stocks of 75mm ammo in the inventory.

With the huge increases in military spending just prior to World War II, money finally became available for improvements to the Army, and the new 105mm howitzer was one of the top priorities. Having spent almost 20 years refining the design, the M2 105mm howitzer was quickly built in large numbers, becoming the standard artillery piece of virtually every infantry division.

The M2 (later to be redesignated the M101) and it variants was a weapon with a sliding horizontal breech block mounted on a conventional split trail carriage. That is, the gun rested over a two wheeled axle and the trails of the carriage would be used to tow it behind its 2-1/2 ton truck prime mover. When emplaced, the trails were split, and spades at the end of the trails were used to dig in the gun and absorb some of the recoil. The gun also had a hydropnuematic recoil system.

TM M2A1 left side

TM M2A1 right side

The tube could elevate to provide plunging fires at long ranges, or be lowered for direct fires if needed. There was a limited ability to traverse the tube on the carriage. If the tube needed to traversed more than that, the trails had to be dug up, the entire carriage moved by lifting and moving the trails, and the gun relaid by the aiming stakes.

The gun fired a 33 pound high explosive projectile using semi-fixed ammunition with a base charge and six increments.

Semi-fixed means that each round came with the projectile, fuze, cartridge case and powder in one complete assembly, much as you’d think of a single round of small arms ammunition. But the projectile could easily be removed from the powder cartridge, and the increments removed as needed to vary the range of the round. The projectile would be placed back onto the cartridge case prior to firing. Between this and the manually operated sliding wedge breechblock, a rapid rate of fire could be achieved.

The 33 pound M1 High Explosive projectile was heavy enough, and had enough explosive power that it could penetrate most earthen field fortifications such as foxholes and bunkers. Fused for instantaneous action (and later with VT) it was devastating against troops in the open. In addition, smoke, illumination and other projectiles were available.

With a range of 12,200 yards, the M2/M101 was well suited for its role as a direct support weapon for the infantry regiments.  Each infantry division would have three 18 gun battalions in the division artillery (three batteries of six guns each) for a total of 54 guns. While division often retained control of the battalions to concentrate on divisional targets, it was very common to see each infantry regiment operating with an artillery battalion in a dedicated direct support role. Often, this infantry/artillery partnership was called a Regimental Combat Team.

The M2/M101 was a very successful design, and remained in front line service well into the 1960s with our Army. In fact, the Canadian Army still uses a modified variant.

Two offshoots of the M2/M101 deserve mention here. First, with the rise of armored divisions in our Army in WWII, it quickly became apparent that self-propelled artillery would be needed to keep up with the fast moving tanks (and their half-track mounted infantry). Surplus M3 Grant tank hulls (and later purpose built M4 tank hulls) were modified to mount the M2 105mm gun.


The resulting M7 Priest was highly successful, remaining in service for many years.

The other offshoot was the M3 105mm gun. Airborne forces were in their infancy during World War II. There was no capability to drop large heavy loads. The only way to bring vehicles and artillery to the airborne battle was by glider. But the M2 was simply too large for the Army’s CG-4 gliders. As a result, airborne divisions had to settle for the old 75mm gun as their divisional artillery.  At least until someone had the idea of a “sawed off” 105mm gun. By reducing barrel length by 27 inches, and by adopting a slightly beefed up version of the 75mm gun’s carriage, the M3 105mm gun would just barely fit into the gliders of the day.  The M3 fired the same projectiles as the M2, but because the shorter barrel length lead to incomplete burning of the powder charge. Faster burning powder charges were developed for the M3. The shorter tube meant that the M3 had a much shorter range, only about 7500 yards.

In addition to serving in the division artillery of the airborne divisions, M3s also served as an infantry support weapon. Each infantry regiment had a 6 gun cannon company. Originally equipped with 75mm guns, by the end of the war, many would be equipped with the M3.

After World War II, with the development of larger tactical airlift planes that could perform heavy drop missions (such as the C-119) the M3 in the airborne division was replaced by the longer ranged M2/M101. Also, some time after WWII, probably during the Pentomic Army reorganization, infantry regiments lost their organic cannon company.

By the early 1960s, the M101 was getting a bit long in the tooth.  The main problem was weight. The 2-1/2 ton weight of the M101 was a bit much for most helos to lift. Accordingly, the M102 howitzer was developed and adopted. The big aim was to reduce weight. The tube basically the same, but an entirely new carriage was adopted. Instead of the classic split trail carriage, a new fixed open box  trail was adopted. Instead of resting on its wheels and using spades at the trail end to provide a stable firing platform, a circular baseplate under the carriage was lowered and staked into position.


Note the circular baseplate firing platform.


One of the last M102s in Iraq, 2004

The lighter weight of the M102 made it easier to move by helicopter, and also allowed for it to be moved by lighter vehicles.  The circular baseplate also meant that the gun could easily be traversed through 360 degrees (or 6400 mils, as the gunners would say). The tube had a manually operated vertical sliding wedge breechblock. The gun used the same ammunition as the M101, and had nearly identical range. It was used in the same role of direct support in the infantry, airborne, and airmobile divisions.

First entering service in the early 1960s, it served throughout the Vietnam War and after. It began to be replaced in the late 1980s, but as you can see from the picture above, it was still in use with some National Guard units as late as 2004.

Mechanized and armored divisions still using the M7 Priest in the late 1950s finally began to replace them with the M108. This self propelled 105mm howitzer shared a common hull and cab structure with the M109 155mm self propelled howitzer. While the M108 was a successful design, however, it was soon decided that heavy divisions would instead use 155mm M109s as the main weapon of the direct support artillery battalions, and the M108 was quickly withdrawn from service.

In the mid-1980s, the US Army began looking to replace the M102, and was deeply impressed with the performance of the British L118 Light Gun in the Falklands. The L118 used separate loading ammunition. After a minor redesign to allow used of existing US semi-fixed ammunition and adopting US fire control and sights, the weapon was adopted as the M119 105mm howitzer and licensed production began at the Rock Island Arsenal. The M119 (and the M119A1 and A2 variants) is the current light howitzer for US infantry, airborne, and air assault brigade combat teams. It can be airlifted by airplanes and helicopters, air-dropped by parachute, towed by a Humvee, and in a real pinch, moved by hand.


M119 firing in Afghanistan

The M119 uses a similar baseplate firing platform to the M102, and features a fixed open box carriage trail of tubular design.

The M119 still uses the same M1 round as the original 105mm howitzers. It’s longer tube does allow for a greater charge to be used, however, and “Charge 8” gives a maximum range of 13,700 meters.  Newer ammunition includes rocket assisted High Explosive rounds (HERA) with ranges of up to 19,500 meters, greatly increasing the area one battery can cover. Somewhat surprisingly, there are no immediate plans to field a GPS guided projectile. The apparent thinking is that Guided MLRS and 155mm Excalibur fires can cover most missions.

Historically, US artillery doctrine has stressed concentration of fires. That is, if an artillery battalion had three targets, rather than having one battery engage each target, the fires of the entire battalion would be dedicated to one target, then the next, and then the third.

But the dispersed nature of the battlefield in Afghanistan means that artillery has to be widely dispersed itself, or many units would have no artillery support in range. Accordingly, it is not uncommon to find single 6 gun batteries or even a two-gun platoon operating independently in support of remote outposts.

The 105mm howitzer has provided over 70 years of faithful service, and there are no plans to replace it.

The M102 105mm howitzer.

12 thoughts on “The 105mm Howitzer”

  1. I myself operated the M101A1 while in the Marine Corps. I was trained on it while a Ft. Sill. Once or twice for dog and pony shows in the field and once at the Chocolate Mountain Gunnery Range for a close air support school (or something, my memories of the specifics are a little faded 20+ years later) out of MCAS Yuma. Damn Phrog crew dropped our howitzer and ammo about half a click apart one day. We had to run all those rounds to the gun position. That was the one and only time we did any helo ops that week.
    Slightly off topic, while an enlisted Field Artillery School student at Ft Sill, early 1988, we were told that there was more artillery at Ft. Sill alone, than in the entire Marine Corps. Up until that point I thought the Marine Corps was huge. Little did I know.
    Back on topic. The M101A1 was my absolute favorite howitzer. Hands down. Small, light, fast firing and easy to maintain. I remember one we used at 29 Palms was manufactured in 1942. If that howitzer could talk, I can only imagine the tales it could tell. I am a little sad that they are not still used for putting steel on target. At least they still live on in a ceremonial capacity. At least in the Marine Corps.

  2. The M101A1 was superior to the M102, and we should have looked to do what the Germans did when looking for a replacement for the 102. They replaced the 22.5 caliber tube with a 34-caliber tube, fitted a muzzle brake, and achieved 16.4km with standard munitions. And it kept 80+ percent standard parts for the M101A1 in the system.

    Silly us. The money saved on development of the M119 should have gone to munitions/propellant development.

    The damned thing was reliable, easy to use, damn near indestructible, especially with the kevlar recoil mechanism sleeve. It may have cost me my right eardrum, but I loved the damned thing.

  3. Were the M102 gun tubes recycled M101 tubes with lots of life still in them, or new production to basically the same design?

    1. New tubes. The breechblock was an entirely different design. The range of the system was pretty much the same. The big benefit over the 101 was decreased weight per gun.

  4. True the M102 weighed about 1,600 pounds less than the M101A1, but I would take the easier emplacement, higher towing speed, and better cross country mobility of the M101A1.

  5. Scott,
    Yeah, significantly. It had a higher axle and wider wheelbase, and was not nearly as prone to flipping.

  6. when in Vietnam this weapon served well..i was a section chief with India 3/12..3rd Mar.Div……..1966-69…We ran into Hot tubes,,round caught in the tube..never had a flat..and the BEE-HIVE rounds worked perfect

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