View source for M102 howitzer

{{Infobox weapon
| name               = M102
| image              = M102 howitzer.jpg
| image_size         = 300
| caption            = The M102 howitzer firing
| origin             = [[United States]]
| type               = [[Howitzer]]
<!-- Type selection -->| is_ranged          = yes
| is_bladed          = 
| is_explosive       = 
| is_artillery       = yes
| is_vehicle         = 
| is_UK              = <!-- Service history -->
| service            = 1964–present
| wars               = [[Vietnam War]] <br /> [[Cambodian Civil War]] <br /> [[Invasion of Grenada]] <br /> [[Gulf War]] <br /> [[Kosovo War]] <br /> [[Iraq War]] <br /> [[Lebanese Civil War]] <br /> [[Salvadoran Civil War]]
<!-- Production history -->| designer           = 
| design_date        = 1962
| manufacturer       = [[Rock Island Arsenal]]
| production_date    = 
| number             = 
| variants           = <!-- General specifications -->
| weight             = {{convert|1,496|kg|lb|abbr=on}}
| length             = Travel: {{convert|6.40|m|ft|abbr=on|sigfig=2}}|
| part_length        = {{convert|3.36|m|ftin||abbr=on}} L/32<ref name="Christopher Chant">{{cite book|last1=Chant|first1=Christopher|title=A Compendium of Armaments and Military Hardware (Routledge Revivals)|date=2013|publisher=Routledge|location=New York|isbn=978-0-415-71068-8|page=99 |url=https://books.google.com/books?id=zUu4AwAAQBAJ&q=%22M102%22+howitzer+%22bore+length%22+OR+%22barrel+length%22&pg=PA99|access-date=29 October 2016}}</ref>
| width              = Travel: {{convert|1.96|m|ftin|abbr=on}}
| height             = Travel: {{convert|1.59|m|ftin|abbr=on}}
| crew               = 8
<!-- Ranged weapon specifications -->| cartridge          = 105 × 372 mm R
| caliber            = {{convert|105|mm|in|abbr=on}}
| action             = Vertical [[Rifled breech loader#The sliding block|sliding-wedge]]
| rate               = Maximum: 10 rpm<br />Normal: 3 rpm
| velocity           = 
| range              = 11.5 km (7.1 miles)
| max_range          = 15.1 km (9.4 miles) with [[rocket-assisted projectile]]
| feed               = 
| sights             = <!-- Artillery specifications -->
| breech             = 
| recoil             = [[Hydraulic recoil mechanism|Hydro-pneumatic]]
| carriage           = [[Gun carriage#Modern gun carriages|Box trail]]
| elevation          = −5° to +75°
| traverse           = 360°
}}

The '''M102''' is a light, [[Towing|towable]] [[105 mm]] [[howitzer]] used by the [[United States Army]] in the [[Vietnam War]], the [[Gulf War]], and the [[Iraq War]].

== Overview ==
The M102 105&thinsp;mm howitzer is used in air mobile (helicopter), attack plane, and light infantry operations. The weapon carriage is lightweight welded aluminum, mounted on a variable recoil mechanism. The weapon is manually loaded and positioned, and can be towed by a 2-ton truck or [[High Mobility Multipurpose Wheeled Vehicle]] (HMMWV), can be transported by [[UH-60 Black Hawk]] helicopters, or can be dropped by parachute with airborne units. When emplaced, the howitzer's high volume of fire compensates in large measure for the lower explosive weight of the projectile compared to the Army's 155 mm and 203 mm howitzers. Since 1964, the Army acquired 1,150 M102 towed howitzers. The weapon is being replaced by the [[M119 howitzer|M119]]-series 105&thinsp;mm howitzer.<ref name="globalsecurity.org">[http://www.globalsecurity.org/military/systems/ground/m102.htm Global Security. Org, M102 105&thinsp;mm Lightweight Towed Howitzer]</ref>

=== Resistance to change ===
Units were initially equipped with the [[M101 howitzer|M101A1 howitzer]], virtually the same 105&thinsp;mm howitzer that had been used to support U.S. forces since [[World War II]]. In 1966 a new 105&thinsp;mm towed howitzer, the M102, was received in Vietnam. The first M102s were issued to the 1st Battalion, [[21st Field Artillery Regiment (United States)|21st Field Artillery]], in March 1966.<ref name="globalsecurity.org" /> Replacement of the old howitzers continued steadily over the next four years.

Many of the more seasoned artillerymen did not want the old cannon replaced. Over the years they had become familiar with its every detail and were confident that it would not disappoint them in the clutch. These experienced artillerymen could offer some seemingly convincing reasons why the M101 was still the superior weapon: its waist-high breech made it easier to load; it had higher ground clearance when in tow; but most important, it was considerably less expensive than the M102.<ref name="globalsecurity.org" /> Their arguments, however, were futile.

The new M102 was substantially lighter, weighing little more than {{convert|1.5|ST}} whereas the M101A1 weighed approximately {{convert|2.5|ST}};<ref name="globalsecurity.org" /> as a result, more ammunition could be carried during heliborne operations, and a 3/4-ton truck rather than a [[M35 2½-ton cargo truck|2½-ton truck]] was its prime mover for ground operations. Another major advantage of the M102 was that it could be traversed a full 360°; the M101A1 had a limited on-carriage traverse, which required its trails (stabilizing legs) to be shifted if further traverse was necessary. The M102 fires the same [[Shell (projectile)#Separate loading cased charge|semi-fixed]] ammunition as the M101, but its longer barrel (32 calibres versus 22 calibres on M101) allows a slightly higher muzzle velocity and thus enhanced firing range.<ref name="Christopher Chant"/> A low silhouette made the new weapon a more difficult target for the enemy, an advantage that far outweighed the disadvantage of being somewhat less convenient to load.

== Design ==
[[File:M1114 towing M102 Howitzer.JPG|thumb|right|M102 howitzer belonging to Battery A, 1-206th FA, is towed north from Camp New York, Kuwait by a M1114 Up-Armored HMMWV.]]
The 105&nbsp;mm howitzer M102 is a lightweight towed weapon, which has a very low silhouette when in the firing position. The M102 howitzer fires a {{convert|33|lb|kg|abbr=on}} projectile of semifixed ammunition and at charge 7 it will fire to {{convert|11.5|km|abbr=on}}. It has a muzzle velocity of {{convert|494| m/s|abbr=on}}. The maximum rate of fire is 10 rounds per minute for the first 3 minutes, with a sustained rate of 3 rounds per minute.<ref name="ReferenceA">TM 9-100-202-14, TM 9-1015-234-12, TM 9-1015-234-10, AND LO 9-1015-234-10</ref>

A roller tire attached to the trail assembly of the M102 permits the weapon to be rotated 6,400 mils (360 degrees) around a firing platform, which provides the pivot for the weapon. It can be elevated from −89 mils (−5 degrees) to a maximum of 1,333 mils (75 degrees). The panoramic telescope has a four power, fixed focus optical system, with 178 mils (10 degrees) field of view. It contains dry nitrogen gas to retard fogging and condensation. The parallax shield used during boresighting protects the lens.<ref name="ReferenceA" />

The trails are made of aluminum alloy. They are a single [[Gun carriage#Modern gun carriages|box trail]] in wishbone shape, and serve three purposes: mobility; stability; and stowage of section equipment. The lunette is the towing pintle that allows the weapon to be connected to the vehicle. When towing, vehicle has a fixed or seized tow pintle; remove the lock plate located under the lunette. The drawbar has two positions: lowered for travel and raised for firing. There are two lifting brackets to connect slings to when the howitzer is being lifted by helicopter. A third bracket is located on front yoke. The carriage handles are used by crew members to lifting and shifting the howitzer during loading, unloading, and emplacing the howitzer.

The firing platform attaches to the howitzer lower carriage by using a socket and a locking handle. The eight holes are for the stakes needed to stake the howitzer in position. Platform stakes are issued in three sizes. There are four {{convert|15|in|cm|abbr=on}} stakes issued for use in frozen or rocky terrain, and are normally issued only where needed, such as extremely cold areas. There are eight {{convert|24|in|cm|abbr=on}} stakes issued, and are used for hard packed ground. Four {{convert|38|in|m|abbr=on}} stakes are issued for use in soft ground.

The first production versions were displayed with a [[muzzle brake]], most likely to allow long range 105&nbsp;mm rounds to be fired, but was discontinued before shipment to Vietnam.<ref>[https://books.google.com/books?id=yykDAAAAMBAJ&dq=popular+science+1930&pg=PA95 "Howitzer Fires In All Directions."] ''Popular Science'', September 1966, p. 95, bottom of page.</ref>

== Current usage ==
[[File:M102 Howitzer A1206 Tai Iraq 2004.JPG|thumb|left|102 Howitzer belonging to Battery A, 1st Battalion, 206th Field Artillery, 39th Brigade Combat Team, in position at Camp Taji, Iraq 29 May 2004]]
While the M102 is no longer in active use by the United States Army, having been replaced by the [[M119 howitzer|M119]], it is  still in use by the [[United States National Guard|National Guard]]. The M102 was last deployed to combat in 2004 by the [[1st Battalion, 206th Field Artillery]], [[Arkansas Army National Guard]].  Seventeen M102 howitzers were deployed to [[Camp Taji]], Iraq. The 1-206th FA provided fire and conducted counter-fire missions in support of [[39th BCT]] operations, an element of the [[1st Cavalry Division (United States)|1st Cavalry Division]]. The 1-206th scavenged spare parts from nine M102 howitzers that were located in the Camp Taji Boneyard.  These howitzers were allegedly captured by the [[Iraqi Army]] during the [[Iran–Iraq War]] in the 1980s.

The M102 is also used on the [[United States Air Force]]'s [[Lockheed AC-130]] gunship. The M102 105&thinsp;mm cannon was modified to be fired from the left rear side door of the AC-130. To accommodate the cannon, the rear side-firing 40&thinsp;mm guns were replaced by the radome that formerly had been installed in the door cavity. That change provided enough space for the 105&thinsp;mm gun to be mounted in the doorway in place of the radome. The gun was first used in the later stages of the Vietnam War.<ref>{{Cite web|url=https://fas.org/man/dod-101/sys/ac/equip/m102.htm|title = M102 105mm Cannon}}</ref> The latest AC-130J Ghostrider gunship was not originally planned to include the 105&thinsp;mm, but designed with enough spare power and room to mount it at some later point.  The Air Force decided to include it in January 2015, starting installation on the third aircraft, then having the first two be retrofitted when guns become available; M102s will be pulled off retiring AC-130Us and put into the AC-130Js.<ref>[http://breakingdefense.com/2015/01/ghostriders-big-gun-ac-130j-gets-105-asap-laser-later/ Ghostrider’s Big Gun: AC-130J Gets 105 ASAP; Laser Later] – Breakingdefense.com, 27 January 2015</ref>

The M102 is used in extremely limited roles by the [[United States Marine Corps]], primarily for firing salutes.

The [[Malaysian Army]] used the M102 during Malaysia's [[Communist insurgency in Malaysia (1968–89)|second communist insurgency]] (1968–1988) to bombard [[Malayan Communist Party|insurgent]] positions on the [[Malaysia-Thailand border]]. The guns were transported by helicopter to remote firing positions. All Malaysian M102s have now been decommissioned and are only used for firing salute.

== Characteristics ==
[[File:M102 plate.JPG|thumb|right|Data plate on an M102 Howitzer]]
* Caliber: 105&thinsp;mm (4.13&thinsp;in)
* Length: 21.8 feet (6.4 m)
* Barrel Length: 32 calibres<ref name="Christopher Chant"/>
* Width: 6.4 feet (2&thinsp;m)
* Height: 5.2 feet (1.6 m)
* Weight: 1.5 tons (1.4 t)
* Crew: 8
* Rate of fire: 10 rounds per minute maximum, 3 rounds per minute sustained
* Range: 11,500&nbsp;m (7.1 miles), 15,100&thinsp;m (9.4 miles) with rocket-assisted projectile

== Operators ==
[[File:U.S. Army artillerymen in Grenada, 1983.jpg|thumb|U.S. [[82nd Airborne Division]] firing an M102 howitzer in [[Operation Urgent Fury|Grenada]], 1983]]
[[File:Quasqueton Veterans Memorial.JPG|thumb|right|[[Quasqueton, Iowa]] Veterans' Memorial with M102 on display]]
* {{flag|Brazil}} 19
* {{flag|El Salvador}} 24
* {{flag|Honduras}} 24<ref>{{Cite web |url=https://www.infodefensa.com/texto-diario/mostrar/3914931/artilleria-centroamericana-pasado-belico-activo-pero-hoy-rezago |title=Artillería centroamericana, pasado bélico y presente incierto |access-date=17 September 2024}}</ref>
* {{flag|Jordan}} 50
* {{KUR}} 84 – Used by the [[Peshmerga]]{{sfn|Military Balance 2016|p=491}}
* {{flag|Lebanon}} 18<ref>{{Cite web |url=http://armstrade.sipri.org/arms_trade/trade_register.php |title=SIPRI Arms Transfers Database |access-date=22 February 2019 |archive-date=5 August 2009 |archive-url=https://web.archive.org/web/20090805014045/http://armstrade.sipri.org/arms_trade/trade_register.php |url-status=dead }}</ref>
* {{flag|Malaysia}} 40<ref name="SIPRI">{{cite web|url=http://armstrade.sipri.org/armstrade/page/trade_register.php|title=SIPRI arms transfer database|date=17 June 2011|publisher=[[Stockholm International Peace Research Institute]]|access-date=17 June 2011|archive-date=14 April 2010|archive-url=https://web.archive.org/web/20100414022558/http://armstrade.sipri.org/armstrade/page/trade_register.php|url-status=dead}}</ref>
* {{flag|Oman}} 36
* {{flag|Philippines}} 24
* {{flag|Saudi Arabia}} 140
* {{flag|Turkey}}
* {{flag|Thailand}} 12
* {{flag|United States}} – Used on the [[Lockheed AC-130#Armament|AC-130J gunships]]
* {{flag|Uruguay}} 15
*{{flag|Vietnam}} – Captured during the [[Vietnam War]]

===Former operators===
* {{flag|Khmer Republic}}
* {{flag|South Vietnam}} – Unknown number used by the [[Republic of Vietnam Airborne Division]]

== See also ==
* [[M101 howitzer]] – previous American 105&thinsp;mm towed howitzer
* [[M119 howitzer]] – current towed 105&thinsp;mm howitzer in US Army service
* [[List of artillery]]
* [[List of crew served weapons of the US Armed Forces]]

== References ==
{{Reflist}}

===Works cited===
* {{cite book |title=The Military Balance 2016 |date=February 2016 |volume=116 |isbn=978-1-85743-835-2 |publisher=Routledge |ref={{harvid|Military Balance 2016}} |author=International Institute for Strategic Studies |author-link=International Institute for Strategic Studies}}

== External links ==
{{Commons category|M102 105 mm howitzer}}
* [https://web.archive.org/web/20070614040604/http://www.army.mil/factfiles/equipment/indirect/m102.html The Army Fact File]
* {{Internet Archive short film|id=gov.dod.dimoc.26968|name=STAFF FILM REPORT 66-19A (1966)}}

{{USAF weapons}}
{{Use dmy dates|date=June 2017}}

[[Category:Cold War artillery of the United States]]
[[Category:Artillery of the United States]]
[[Category:Aircraft artillery]]
[[Category:Field artillery of the Cold War]]
[[Category:105 mm artillery]]
[[Category:Military equipment introduced in the 1960s]]