M56 Scorpion

• Name — M56 Scorpion • Origin — United States • Type — Self-propelled gun • Is Vehicle — yes • Used By — See Operators • Wars — Vietnam War Western Sahara War • Manufacturer — Cadillac Motor Car Division of General Motors • Production Date — 1953–1959 • Number — 325 • Weight — 7.1 t • Length — 4.55 m (excluding gun) 5.84 m (overall) • Width — 2.57 m • Height — 2.05 m over gun shield • Crew — 4 (commander, gunner, loader and driver) • Armour — unarmored except for blast shield • Primary Armament — 90 mm M54 Gun 29 rounds • Engine — Continental AOI-403-5 gasoline engine • Engine Power — 200 bhp • Transmission — Allison CD-150-4, 2 ranges forward, 1 reverse • Fuel Capacity — 210 L • Suspension — Torsion tube over bar at wheels 1 and 4, torsion bar at wheels 2 and 3 • Clearance — 0.32 m • Vehicle Range — 230 km • Speed — 45 km/h

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 South Korea. With a crew of four (commander, gunner, loader and driver), the M56 weighed 6.4 t empty and 7.7 t combat-loaded. It had infrared driving lights but no NBC protection 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 AOI-403-5 gasoline engine developing 200 bhp at 3,000 rpm, allowing a maximum road speed of 28 mph and a maximum range of 140 mi. Twenty-nine rounds of main gun ammunition were carried, and only the small 5 mm thick blast shield was armored.

• Illustration — M56 Scorpion of 16th Armor, US 173rd Airborne Brigade firing at Viet Cong during Operation Toledo 17 June 1966 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, where it was used mainly in direct fire-support. 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 M50 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 the only export customer which used M56 Scorpions in combat. M56 Scorpions were deployed against Polisario rebels during the Western Sahara War. A number of examples were made available to South Korea but not used.

• Illustration — Map of former M56 operators in red

* •: 5 exported in 1965. Used by Tercio de Armada from 1966 to 1970 •: 1 for evaluation in 1960 •: 87 received in 1966-1967 •: 60 ex-American M56 were left as surplus but never used • Illustration — An APC based on the Scorpion

• Illustration — Diorama of destroyed M56 at the AAF Tank Museum. Note the prominent rubber tires on the road wheels. • Illustration — The outdoor display of M56 Scorpion 1740950 at VFW Post 2524, Culpeper, VA. United States • American Legion Post 8 in Guntersville, Alabama. • Two of them can be found in The American Military Museum in South El Monte, California. • American Legion post in Duluth, Georgia. • Ropkey Armor Museum in Crawfordsville, Indiana • Veterans Memorial Stadium in Cedar Rapids, Iowa. • Iowa Gold Star Museum at Camp Dodge in Johnston, Iowa. • Combat Air Museum at the former Forbes Field, in Topeka, Kansas. • Forest Hill Station in Millersburg, Kentucky. • Boyd County War Memorial in Armco Park in Summit, Kentucky. • Oldtown VFW Post 9451, Oldtown, Maryland. • Collings Foundation in Stow, Massachusetts. • Mississippi Armed Forces Museum, Camp Shelby, Mississippi. • Disabled American Veterans Belleville Hall, Belleville, New Jersey. • Elmwood Park, New Jersey. • 82nd Airborne War Memorial Museum in Fort Bragg, North Carolina. • Fort Sill, Oklahoma • 45th Infantry Museum in Oklahoma City, Oklahoma. • Corner of Elk St. and 3rd St., Elkton, South Dakota • American Legion Hall, Post 88, in Donelson, Tennessee. • Texas Military Forces Museum, Camp Mabry in Austin, Texas. • Veterans of Foreign Wars Post 2524 Culpeper, Virginia. • American Armored Foundation Tank Museum in Danville, Virginia, along with a diorama of a destroyed M56. • Auburn, Washington. • Tillicum Park in Forks, Washington. • National Museum of Military Vehicles in Dubois, Wyoming South Korea • One former Republic of Korea Army example on display at the War Memorial of Korea. New Zealand • One example in M&M Military Vehicle Museum (Private Museum) under restoration.