During World War 2 (1939-1945), the Italian Army joined its Axis counterpart in Germany in appreciating the battlefield value of the "assault gun" when attempting to dislodge a determined foe. As such, a myriad of tracked vehicles emerged through design and development that attempted to mate the chassis of an existing combat tank with an effective howitzer. Often times, these creations utilized a short profile armored hull superstructure which fixed the armament within, providing limited traversal and elevation reaches. Other times, the guns were simply mounted atop the tank chassis (its turret having been removed) with the crew operating in an open-air environment while being exposed to all sorts of battlefield dangers - though this method eased production and reduced the material commitment.
As Italian industry struggled to keep up with the Army demand for such weapons, the Ansaldo concern attempted a low-cost solution in the "Semovente da 149/40". This design mated the chassis of the Carro Armato M15/42 Medium Tank with the potent 150mm Cannone da 149/40 modello 35 howitzer to produce an open-air, tracked assault gun system. The vehicle was powered by an SPA gasoline-fueled engine of 250 horsepower and provided a maximum road speed of 22 miles per hour. Armor protection (for only the driver and vehicle components) reached 14mm thick. The hull was suspended atop a leaf spring suspension for some inherent cross-country capabilities. Overall weight of the vehicle was 24,000 kg with a length reaching 22 feet, a width of 9.8 feet, and a height of 6.6 feet. Eight double-tired road wheels were fitted to four individual bogies at each hull side. The drive sprocket sat at front along with the engine compartment and driver's position. The gun and mounting hardware was concentrated over the rear of the vehicle.
The first pilot vehicle was readied for trials in 1942 though the promising system was derailed by overcommitted Italian industry and the eventual surrender of the country to the Allies in September of 1943. The gun selected for the Semovente da 149/40 was to give a sound reach on the battlefield and would have negated the limitation of its open-air design concerning the gunnery crew. Nevertheless, only a sole prototype was ever completed, bringing about the end to the vehicle in Italian Army plans moving forward. Its hulk once made up the impressive outdoor display of the U.S. Army Ordnance Museum.