The M113 is a fully tracked armored personnel carrier manufactured by BAE Systems. The vehicle was first fielded by United States Army’s mechanized infantry units in Vietnam in April 1962. The M113 was the most widely used armored vehicle of the U.S. Army in the Vietnam War, earning the nickname ‘Green Dragon’ by the Viet Cong as it was used to break through heavy thickets in the midst of the jungle to attack and overrun enemy positions, but largely known as an APC and ACAV (armored cavalry assault vehicle) by the allied forces.
The M113 introduced new aluminum armor that made the vehicle much lighter than earlier vehicles; it was thick enough to protect the crew and passengers against small arms fire but light enough that the vehicle was air transportable and moderately amphibious. In the U.S. Army, the M113 series have long been replaced as front-line combat vehicles by the M2 and M3 Bradley, but large numbers are still used in support roles such as armored ambulance, mortar carrier, engineer vehicle, command vehicle, etc. The Army’s Heavy Brigade Combat Teams are equipped with around 6,000 M113s and 4,000 Bradleys.
The M113’s versatility spawned a wide variety of adaptations that live on worldwide, and in U.S. service. These variants together represent about half of U.S. Army armored vehicles today. To date, it is estimated that over 80,000 M113s of all types have been produced and used by over 50 countries worldwide, making it one of the most widely used armored fighting vehicles of all time. The Military Channel’s “Top Ten” series named the M113 the most significant infantry vehicle in history. The U.S. Army planned to retire the M113 family of vehicles by 2018, seeking replacement with the GCV Infantry Fighting Vehicle program, but now replacement of the M113 has fallen to the Armored Multi-Purpose Vehicle (AMPV) program.
The basic M113 armored personnel carrier can itself be fitted with a number of weapon systems. The most common weapon fit is a single .50 caliber M2 machine gun. However, the mount can also be fitted with a 40 mm Mk 19 automatic grenade launcher. A number of anti-tank weapons could be fitted to the standard variant: the U.S. Army developed kits that allowed the M47 Dragon and BGM-71 TOW anti-tank missile systems to be mounted. In the case of the M47, the system mated to the existing machine gun mount, without having to remove the machine gun. This allowed the commander to use the weapon, as well as the machine gun. A large array of turrets and fixed mounts are available to mount high explosive cannon from 20 mm to 105 mm to the M113 series making them function also as assault guns and fire support means; while in many cases still having room inside to carry dismounted infantry or cavalry scouts.
The M113 is built of 5083 aircraft-quality aluminum alloy which gives it some of the same strength as steel at a slightly reduced weight, as the greater thickness allows structural stiffness.
Its weight allows the use of a relatively small engine to power the vehicle, a 6V53 Detroit 2-stroke six cylinder diesel, with an Allison TX-100-1 3-speed automatic transmission, and allows the vehicle to carry a large payload cross-country and to be transported by fixed- and rotary-wing aircraft. Original-production M113s can swim without deploying flotation curtains, using only a front-mounted trim vane; propelled in the water by their tracks.
Original version, powered by 209 hp (156 kW) Chrysler 75M V8 petrol engine.
Starting in 1964, the gasoline engine was replaced with a 215 hp (160 kW) 6V-53 Detroit Diesel engine, to take advantage of the better fuel economy and reduced fire hazard of the diesel engine. The suffix A1 was used on all variants to denote a diesel engine, i.e. an M106A1 was an M106 mortar carrier equipped with a diesel engine.
In 1979 further upgrades were introduced. Engine cooling was improved by switching the locations of the fan and radiator. Higher-strength torsion bars increased ground clearance, and shock absorbers reduced the effects of ground strikes. Armored fuel tanks were added externally on both sides of the rear ramp, freeing up 16 cubic feet of internal space. The weight of the M113A2 was increased to 25,880 lbs. Because the added weight affected its freeboard when afloat, it was no longer required to be amphibious. Four-tube smoke grenade launchers were also added. The suffix A2 is used on all variants to denote upgrade to A2 standard.
In 1987, further improvements for “enhanced (battlefield) survival” were introduced. This included a yoke for steering instead of laterals, a more powerful engine (a 6V-53T Detroit Diesel), external fuel tanks and internal spall liners for improved protection. The suffix A3 is used on all variants to denote upgrade to A3 standard.
M113 Armored Cavalry Assault Vehicle (ACAV) variant
The “Armored Cavalry Assault Vehicle” or “ACAV”, was a concept and field modification pioneered by the South Vietnamese Army (ARVN) in 1963 during the Vietnam war, ARVN troops utilized the M113 armored personnel carrier as an infantry fighting vehicle, and more often than not, as a light tank by fighting mounted rather than as a “battle taxi” as dictated by U.S. Army doctrine.
After it was found that the commander and cargo hatch positions were extremely exposed and the commander and troops hence vulnerable to enemy fire, the South Vietnamese engineers thought out a simple and cheap remedy to this problem: Initially field expedient shields and mounts were made from sunken ships, but this was soft metal and could be penetrated by small arms fire. Finally armor plate, from scrapped armored vehicles was used; this worked well, and by the end of 1964 all ARVN ACAVs were equipped with gun shields. For the US Army, ACAV sets were produced industrially in Okinawa for the .50 cal. machine gun, and rear aft and starboard M60 machine gun positions. Finally, the ARVN’s ACAV modifications were adopted by the US Army in Vietnam, and by 1965 the full ACAV set was mass-produced in the U.S. The kit included shields and circular turret armor for the commander’s M2 .50 caliber machine gun, and two additional 7.62 mm M60 machine guns, again with shields, fitted on either side of the top cargo hatch. This kit could be retrofitted to any M113. ACAV sets were sometimes fitted to the M106 mortar carrier, but the different rear hatch found on this vehicle required the left M60 machine gun to be fitted to the extreme rear instead of the side. Many kits were added in the field, but at least in the case of the 11th Armored Cavalry Regiment, the vehicles had their ACAV sets installed in the U.S. prior to their deployment to Vietnam in 1966 from Ft. Meade, Maryland. Additional armor in the form of a mine protective kit under the hull was also frequently fitted.
|Weight||12.3 tonnes (13.6 short tons; 12.1 long tons)|
|Length||4.863 metres (15 ft 11.5 in)|
|Width||2.686 metres (8 ft 9.7 in)|
|Height||2.5 metres (8 ft 2 in)|
|Armor||aluminum 12–38 millimetres (0.47–1.50 in)|
|M2 Browning machine gun|
|varies (see text)|
|Engine||Detroit Diesel 6V53T, 6-cylinder diesel engine
275 hp (205 kW)
|Suspension||torsion bar, 5 road wheels|
|480 km (300 mi)|
|Speed||67.6 km/h (42.0 mph), 5.8 km/h (3.6 mph) swimming|