M116 howitzer

The 75mm pack howitzer M1 was a pack howitzer designed in the United States. The gun saw combat in World War II with the United States Army and the United States Marine Corps, and was also supplied to foreign militaries. Initially designed to be moved across difficult terrain, the gun and carriage could be broken down into several pieces to be carried by pack animals, and this ability as well as its compact size allowed it to be used by paratroop and glider forces
In addition to the pack or air-portable configuration, the gun was also mounted on a split-trail carriage to serve as a field artillery piece. The M1 in its original version was mated to a number of self-propelled carriages, though only one of those – 75 mm HMC T30 – reached mass production, while he M2 and M3 variants were vehicle-mounted in the 75 mm HMC M8 and some LVT models.

Development and production

The 75 mm pack howitzer was designed in the United States in the 1920s to meet a need for an artillery piece that could be moved across difficult terrain. Development began in 1920, and in August 1927, the weapon was standardized as howitzer, pack, 75mm M1 on carriage M1. Due to meager funding, production rates were very low; by 1933, only 32 guns had been manufactured, and by 1940, only 91 pieces. It was not until September 1940 that the howitzer was put into mass production. By then, the M1 had been succeeded by the slightly modified M1A1. Production continued until December 1944.
The only significant changes during the mass production period were carriage improvements. The original carriage M1 was of the box trail type, with wooden wheels. The requirement for a lightweight howitzer for airborne troops led to the introduction of the M8 carriage, similar except for new wheels with pneumatic tires.
Another requirement, from the United States Cavalry, resulted in a completely different family of "field howitzers" mounted on split trail rather than box trail carriages. However, only limited numbers of the M1 field howitzer variant were built because of the Cavalry branch's rapid switch to self-propelled guns.

Year	1940	1941	1942	1943	1944	Total
Pack howitzers, pcs.	36	188	1,280	2,592	915	4,939
Field howitzers, pcs.	–	234	64	51	–	349

Description

The howitzer M1 or M1A1 consisted of the gun tube and breech, joined together by interrupted threads, allowing for quick assembly and disassembly. One-eighth of a turn was required to connect or disconnect the two elements. The tube had uniform, right-hand rifling with one turn in 20 calibers. The breech was of horizontal sliding-block type, with a continuous-pull firing mechanism. The recoil system was hydro-pneumatic, with the buffer and recuperator under the barrel.
The pack howitzer carriage M1 was of box trail type, and originally had steel-rimmed wooden wheels. For transportation, the howitzer M1 or M1A1 on carriage M1 could be broken down into six loads for pack animals, with weights between and each:

Tube
Breech and wheels
Top sleigh and cradle
Bottom sleigh and recoil mechanism
Front trail
Rear trail and axle.

The carriage M8 was identical except for the axle arms and wheels, which were metal with pneumatic tires. The howitzer on carriage M8 could be broken down into seven mule loads or into nine parachute loads. It could also be towed by a vehicle such as a 1/4 ton jeep, or transported by plane or glider such as the CG-4 Waco.
In contrast, the field howitzer carriages were non-dismantling, and were fitted with metal wheels with pneumatic tires. They also had an additional retractable support, referred to as a firing base; in the firing position, the base could be lowered and the wheels raised, leaving the weapon to rest on the firing base and trails.

Organization and service

US military

In the Second World War era US Army, 75 mm howitzers were issued to airborne and mountain units.
An airborne division, according to the table of organization and equipment of February 1944, had three 75 mm howitzer battalions – two glider field artillery battalions and one parachute field artillery battalion.
The only mountain division formed, the 10th, had three 75 mm howitzer battalions, with 12 pieces each. The gun was also used by some separate field artillery battalions. These included mule-packed field artillery battalions seeing service in Burma.
The M1A1 also saw use during the Battle of Anzio, 39th Field Artillery Regiment.
In the US Marine Corps, under the "E-Series" T/O&E from 15 April 1943, the divisional artillery included three 75 mm howitzer battalions with 12 pieces each. The F-series T/O&E from 5 May 1944 reduced the number of 75 mm battalions to two, while the G-series T/O&E removed them altogether and marked a completion of the shift to 105 mm and 155 mm howitzers. Although the G-series T/O&E was only adopted officially on 4 September 1945, in practice many changes contained in the table were introduced early in 1945.
The M116 is still used by the US military for ceremonial purposes as a salute gun firing blanks.

Other operators

Two major lend lease recipients of the M1 were United Kingdom and China. 68 pieces were supplied to France, and 60 to various countries in Latin America.
In British service, the howitzer was issued to two mountain artillery regiments, two air-landing light artillery regiments, raiding support regiment and was temporarily used by some other units. The gun remained in British service until the late 1950s.
The 75 mm howitzer was also used by Australian forces – two mountain batteries and some other units.
A single howitzer was airdropped in April 1945 to the 2nd SAS Regiment, a special force coordinated by Major Roy Farran and composed of partisans with mixed political allegiances, Russian ex-prisoners-of-war, and Wehrmacht deserters. Baptized "Molto Stanco", the gun was used in the course of Operation Tombola to harass enemy convoys driving up and down along Route 12 between Modena and Florence. On 21 April 1945, the howitzer was towed by means of a Willys Jeep to the outskirts of Reggio Emilia, from where the Italian gunners initiated a shelling of the city that wrought panic among Axis troops. Believing that the arrival of Allied forces was imminent, the Germans and their fascist allies evacuated the city.
In China after the loss of the mainland, guns left behind were seized by the People's Liberation Army and used during the Korean War. There is record of these guns being used at the Siege of Dien Bien Phu and, presumably, in later conflicts. The type also remained in use with the Republic of China Army's outlying island garrisons as well as mountain troops.
File:Baterije brdske artilerije v bojih pri Kninu.jpg|thumb|M1s of the Artillery brigade of the 8th Dalmatian Corps during Battle of Knin, 1944
153 M116s were supplied to Japan and they were used until the 1980s. The Croatian Army fields M116 howitzers as ceremonial cannon, 12 of which are still kept in service for that purpose; an additional 45 guns have been retired and are no longer utilized by the army, some being stored in local army museums.
In 2010, the M116 75 mm pack howitzer was used by the Turkish Army in operations against Kurdish separatists in southeastern Turkey.
The howitzers have been used for avalanche control at several western US ski areas.
Three howitzers are used by Norwich University's Norwich Artillery Battery, along with a Civil War-era cannon used for ceremonies. The howitzers are used in field training exercises for both the Battery and the school's Ranger Company and the Corps of Cadets, as well as school traditions, such as at football game kickoffs. The University of North Georgia, one of six senior military colleges also utilizes a pack howitzer at the base of their drill field. The piece is fired daily during reveille, retreat and during any special ceremonies honoring military graduates or active duty personnel.

Variants

Howitzer variants:
*M1920, M1922A, M1922B, M1923B, M1923E1, M1923E2 – prototypes.
*M1 – the first standardized variant. Based on M1923E2 with minor changes
*M1A1 – variant with modified breech block and breech ring
*M2 – vehicle mounted variant. Tube and breech from M1A1 were used. In order to provide a cylindrical recoil surface, the tube was fitted with an external sleeve. 197 built.
*M3 – vehicle mounted variant. Similar to M2 but with recoil surface as a part of the tube. The M2 and M3 barrels were interchangeable.
*M116 – post-war designation of the complete weapon
*M120 – post-war designation for saluting howitzers, can only fire blanks
Carriage variants:
*M1 – dismantling box trail carriage with wooden wheels
*M2A1, T2, T2E1, T2E2, T2E3 – experimental carriages
*M3A1 – split-trail carriage with firing base and pneumatic tires
*M3A2 – M3A1 with shield added
*M3A3 – M3A2 with different wheels and combat tires
*M8 – M1 with new wheels with pneumatic tires

	M1A1 on carriage M1	M1A1 on carriage M8	M1A1 on carriage M3A3
Carriage type	box trail	box trail	split trail
Wheels	wooden, with steel rims	steel, with pneumatic tires	steel, with pneumatic tires
Shield	none	none	+
Length
Width
Height
Combat weight
Travel weight
Elevation	+5° to +45°	+5° to +45°	+9° to +50°
Traverse	6°	6°	45°
Transportation	6 mule loads	1/4 ton 4x4 truck, 7 mule loads, 9 parachute loads, plane or glider	1/4 ton 4x4 truck