The XM97 Scorpion is the result of a complex program started in 1981 at the advent of the Paternian XM5 Victoria. Cuban military engineers at HDI took the XM5s turret and mated it to a hull that had been in development since late 1978. They took the original 120mm cannon and replaced it with the experimental XM3 120mm cannon. The tank comes with a crew of four: Commander, Gunner, Loader, and Driver. Armor is made of a composite involving tungsten, titanium, and a few classified materials to ensure maximum crew survivability. The vehicle is powered by an HDI-AOS-708 multi-fuel air-cooled engine. The program was complete in 1983 and the first 40 M97 Scorpions were delivered to 2nd Battalion, 1st Armored in early 1984. This particular model, the E4, was the final prototype variant before mass production began.