The M56 (sometimes called the "Scorpion") was a fully tracked 90mm gun developed in the 1950s to provide airborne troops with a mobile anti-tank weapon. As such the system was used by airborne battalions and airborne infantry tank companies in the 1960s. The M56 Scorpion was also known as the SPAT for Self-Propelled Anti-Tank. Hull construction of the M56 consisted of an all-welded and riveted aluminum. The standard 90mm main gun was closely associated with the main gun as found on the M47 Patton Tank.
One major drawback of the M56 was that the crew of the M56 was exposed to the elements, with the exception of the blast shield and a windscreen for the driver. The loader utilized a folding stage from which to stand on to reload the weapon system. Despite this complete lack of crew protection, the system was a formidable piece of mobile artillery, particularly given the fact that it would be made available to frontline airborne units. Couple that with the maximum range of the main gun set out to 1,500 meters and the benefits appear to outweigh the drawbacks. Another major drawback was in the force of the recoil of the main gun which would literally tilt the entire system up and backwards when the weapon was fired along with produce an absorbent amount of dust and smoke in the process.
The M56 had a lifespan with the United States 82nd Airborne and 101st Airborne up until the 1960's to which the system gave way to the M551 Sheridan. Despite this replacement, the M56 was in fact fielded in the Vietnam War in limited numbers, yet relegated to the fire support role. The chassis would also be featured in several less noteworthy roles including that of an APC, mortar carrier and a recoilless rifle tank.
Designation: M56 Scorpion
Classification Type: Airborne Self-Propelled Anti-Tank Gun
Contractor: Cadillac Motor Car Division of General Motors Corp - USA
Country of Origin: United States
Initial Year of Service: 1953