The American M113 Armored Personnel Carrier became one of the most successful Cold War vehicles in the world with operators numbering over sixty nations and production reaching over 80,000 units. The vehicle made its way into operational service during 1960 and served with American and Australian forces during the Vietnam War (1955-1975). From there, its global reach was such that the carrier went on to see combat actions in the Yom Kipper War (1973), the Invasion of Panama (1989-1990), the Iran-Iraq War (1980-1988), the Persian Gulf War (1991), the War in Kosovo (1998-1999), and the recent wars in Afghanistan (2001-Present) and Iraq (2003 - 2011) while also being featured in less publicized conflicts. The chassis has also proven hugely adaptable and has served as the basis for a plethora of other related battlefield variants. Despite its 1950s-era design, the M113 remains a frontline participant for many nations today (2014).
Development on the 13.5-ton tracked vehicle began in 1956 to help fulfill a U.S. Army requirement for an air-transportable Armored Personnel Carrier (APC). The vehicle would be compact enough to fit into the cargo hold of a Lockheed C-130 Hercules transport or similar. FMC Corporation (Food, Machinery and Chemical Corp) then returned with two possible vehicles - the aluminum T113 and the steel T117 pilot vehicles to which the Army selected the aluminum version. This made it the first armored military vehicle to be constructed primarily of aluminum when steel was traditionally used. Its production model counterpart then became the M113 to which the model was standardized in the U.S. Army inventory in 1959 and replaced the stock of FMC M59 APCs then in service.
Production began in 1960 from FMC San Jose and these early-batch forms showcased a gasoline-fueled engine, a pintle-mounted 0.50 caliber M2 Browning heavy machine gun, and were (borderline) amphibious by design (propelled in the water by the motion of its tracks). The driver sat in a position at the front-left of the boxy hull superstructure with access possible through a roof hatch. His position also held four periscopes for viewing while "buttoned down" and also supported an infrared scope for low-light operations. Steering of the vehicle was through traditional levers. The glacis plate was mildly sloped for basic ballistics protection while all other sides of the hull were vertical in their angle. A hydraulically-powered ramp at the rear of the vehicle provided easy access to the passenger cabin and held a smaller access door within its frame. The vehicle commander was also granted use of a dedicated roof hatch at his position located behind the driver. He held access to five periscopes for increased situational awareness and a single 0.50 caliber M2 Browning heavy machine gun was a standard armament fitting at his hatch. Occupants could also engage in an firefight through a hatch over the passenger cabin. The internal configuration of the M113 was such that the powerpack was installed in the front-right of the hull along with the drive sprocket. There were five road wheels to a hull side in play with the track idler at rear. Beyond the two crew, eleven infantry could be carried in the rear cabin. Armor protection ranged from 12mm to 38mm. These vehicles reached operational-level readiness during 1962-1963.
During May of 1963, manufacture had shifted to a diesel-fueled variant (Detroit Diesel 6V53 V-6) known as the M113A1 which reduced the chance of fire if pierced in combat and offered increased operational road ranges as a result. The new engine was mated to an Allison TX-100 transmission system. This variant appeared in useful numbers from 1964 onwards. The developmental M113E1 brought about more changes to the base design including improved suspension and engine cooling and showcased features and qualities to become standard in future M113 marks.
The next major improvement to the line did not occur until after the Vietnam War and this was in 1979 with the arrival of the M113A2 mark. The goal of engineers was to figure out ways to wring about performance gains from the existing vehicle - now nearly 20 years old. Externally, the M13A2 was largely indistinguishable from its A1 counterpart but was set apart by its list of gains: the suspension system was overhauled and included increased ground clearance while engine cooling was address again. There was support for optional externally-mounted fuel tanks which increased operational ranges and these were fitted to either side of the rear ramp door. A turbosupercharger was installed on the engine and an Allison X200-3 crossdrive transmission used. The changes added nearly 1.5 feet to the length to the M113 hull while an additional 900lbs of weight was gained.
Appearing in 1987 was a major revision of the M113 line through the new M113A3 model. This mark mated the Allison X200-4 transmission system to the all-new Detroit Diesel 6V-53T turbocharged diesel engine. The suspension system was addressed yet again and the optional external fuel tanks were fitted as standard. The internal tanks were given spall liners for improved protection for the crew and passengers. The steering levers were now replaced by a more conventional automobile-style wheel with foot pedals. TheP-900 armor kit was also supported which allowed for even greater protection against emerging battlefield threats of the period.
Production of the M113 originally ended in 1992 though additional orders allowed for further manufacture to continue. License local production was also undertaken in Italy by OTO Melara and by BMF of Belgium. Final U.S. Army purchases of M113s was in 2007 to which the service has maintained several thousand in its fleet, many of the A2 and A3 models and upgraded for better range, firepower, performance, and survivability (including use of applique armor kits). While no direct successor is in sight, several developments have emerged as possible replacements including the proposed Armored Multi-Purpose Vehicle (AMPV). The original proposal request emerged in early 2013.
As stated earlier, the chassis (and sometimes hull) of the M113 have gone on to serve in a myriad of other useful battlefield guises. There was the M58 "Wolf" smoke screen generator vehicle and the M106/M125 mortar carriers. The M150 was outfitted with the TOW Anti-Tank Guided Missile (ATGM) launcher and this was revised as the M901 ITV (Improved TOW Vehicle). The M113 forms the M163 20mm "Vulcan" air defense vehicle and the M48 "Chaparral" air defense missile carrier. The M548 is a cargo hauler, the M577 a dedicated command vehicle and the M579 a repair vehicle. The M806 was developed into an Armored Recovery Vehicle (ARV) with the M981 FIST-V (FIre Support Team - Vehicle) being based on the M901. The M132 line was a dedicated flame tank and the XM734 was a proposed Infantry Fighting Vehicle (IFV) form. Variants go far beyond this listing due to operator requirements, locally-produced versions, many locally modified forms. The ACV-300 is a Turkish version of the M113 while the Taiha is a Pakistani model. The Italian version is the VCC-1 and Norway uses the NM135/NM142 designations for the M113A1 and M113A2 respectively.
Despite its general external similarity to the M113, the subsequent (and dimensionally smaller) M114 vehicle was a new tracked system adopted by the U.S. Army and intended for the reconnaissance role. the M75 (1952) and M59 (1953) APCs also share the same shape. The M59 was the M75's replacement. The M59 was replaced by the M113.