M56 Scorpion

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M56 Scorpion
M56 at AAF Tank Museum.JPG
M56 Scorpion preserved at the American Armored Foundation Tank Museum in Danville, Virginia.
TypeSelf-propelled gun
Place of originUnited States
Service history
Used bySee Operators
WarsVietnam War
Western Sahara War
Production history
ManufacturerCadillac Motor Car Division of General Motors
No. built325
Mass7.1 tonnes (16,000 lb)
Length4.55 metres (14 ft 11 in) (excluding gun)
5.84 metres (19 ft 2 in) (overall)
Width2.57 metres (8 ft 5 in)
Height2.05 metres (6 ft 9 in) over gun shield
Crew4 (commander, gunner, loader and driver)

Armorunarmored except for blast shield
90 mm M54 Gun
29 rounds
EngineContinental A01-403-5 gasoline engine
200 brake horsepower (150 kW)
TransmissionAllison CD-150-4, 2 ranges forward, 1 reverse
SuspensionTorsion tube over bar at wheels 1 and 4, torsion bar at wheels 2 and 3
Ground clearance0.32 m (1 ft 1 in)
Fuel capacity210 litres (46 imp gal; 55 US gal)
230 kilometres (140 mi)
Speed45 kilometres per hour (28 mph)

The M56 Scorpion is an American unarmored, airmobile self-propelled anti-tank gun, which was armed with a 90mm M54 gun with a simple blast shield, and an unprotected crew compartment.


The M56 was manufactured from 1953 to 1959 by the Cadillac Motor Car Division of General Motors for use by US airborne forces, though the vehicle was eventually used by the Spanish Navy Marines, Morocco and the Republic of Korea as well. With a crew of four (commander, gunner, loader and driver), the M56 weighed 6.4 tonnes (14,000 lb) empty and 7.7 tonnes (17,000 lb) combat-loaded. It had infrared driving lights but no Nuclear, Biological and Chemical (NBC) protection system and was not amphibious.

The M56 was a fully tracked vehicle with rubber-tired run-flat road wheels and front drive sprocket wheels. It was powered by a Continental A01-403-5 gasoline engine developing 200 brake horsepower (150 kW) at 3,000 rpm, allowing a maximum road speed of 28 miles per hour (45 km/h) and a maximum range of 140 miles (230 km). Twenty-nine rounds of main gun ammunition were carried, and only the small 5mm thick blast shield was armored.

In service[edit]

The M56 saw combat service with U.S. forces in the Vietnam War. It was deployed with the 173rd Airborne Brigade, which was the only Airborne Brigade deployed with the M56,[1] where it was used mainly in a direct fire-support role. Its function as an air-mobile, self-propelled, anti-tank vehicle was eventually replaced in Vietnam by the troubled but effective M551 Sheridan which had a fully armored turret. The USMC used the Ontos, which had an armored cabin and was armed with recoilless rifles, in a similar role (the running gear of the first Ontos prototype was the same as on the M56, but it was replaced for the production variant).

As for foreign operators, Morocco was only export customer which had used M56 Scorpions in actual combat. M56 Scorpions were deployed against Polisario rebels during Western Sahara War.[citation needed]


Map of former M56 operators in red

Former operators[edit]


Diorama of destroyed M56 at the AAF Tank Museum. Note the prominent rubber tires on the road wheels.

United States

South Korea

See also[edit]


  1. ^ Rottman, Gordon L.; Anderson, Duncan (22 April 2008). The US Army in the Vietnam War 1965-73. Bloomsbury USA. ISBN 9781846032394 – via Google Books.
  2. ^ a b c Estes 2016, p. 44.
  3. ^ Estes 2016, p. 46.

External links[edit]