The M13/40 was the next logical evolution of the M11/39 medium tank series of 1939 and introduced improved armor protection as well as a more potent main gun while introducing a diesel-fueled powerplant and improved defensive armament. The M13/40 was brought online to replace previous Italian tank offerings including the L3, L6/40 and M11/39 and the arrival of the M13/40 directly replaced the M11/39 in production at the time. Some 779 M13/40s were produced in whole with most of these under the Ansaldo-Fossati brand. Despite her 14 ton weight, the Italian Army classified the M13/40 as a "medium tank" for the "M" in her designation stood for "Medio" and was based on Italian Army naming conventions of the time. The M13/40 was delivered to awaiting Italian tankers in Libya in 1940.
Design of the Carro Armato M13/40 series was conventional throughout. Its long running, side-mounted track systems sported the drive sprocket at the front of the assembly with the track idler at the rear. There were three track return rollers along the top portion of the track system with no fewer than eight small, paired road wheels with two wheels per bogey and two of these bogies per suspension installation. The hull was suspended from the wheels by a leaf-spring bogie system with the chassis itself was based on the earlier M11/39 series. The running gear of the tank was heavily influenced by Italian usage of the British Vickers 6-Ton tank prior to the war - the Vickers 6-Ton being a very popular light tank that went on to influence several other designs before the war. The hull featured a heavily sloped glacis plate (nearly horizontal) and fixed superstructure with slightly sloped facings. The turret assembly was mounted to the top of the superstructure and provided for a tall profile. Construction was riveted steel with 42mm armor thickness along critical facings.
Power for the M13/40 series was derived from a single fitting of a SPA TM40 V8 diesel engine. This powerplant developed up to 125 horsepower and was fitted to the rear of the hull with a shaft driving the front sprockets. This allowed the vehicle to reach top speeds of 20 miles per hour on level roads (lesser so off road) with a range out to 120 miles. The 120 mile range was actually an excellent quality of the tank while her 20 mile per hour top speed was rather slow for such a light tank design (despite her classification as a medium tank). Overall weight was in the vicinity of 14 tons.
The Carro Armato M13/40 was crewed by four personnel made up of the driver, tank commander, main gunner and machine gunner. The driver maintained a front-left seating in the hull with the machine bow machine gunner to his immediate right. This machine gunner also doubled as the tank radio operator, a practice consistent with the times. However, radios were not fitted as standard equipment to all of the completed M13/40s. The commander and gun layer both resided in the cramped turret. Access to the turret was through a two-piece hatch on the roof. The hull crew managed with a left-side rectangular hatch along the superstructure.
Primary armament for the series was the 47mm Cannone da 47/32 M35 main gun. 104 x 47mm projectiles were afforded to the gunnery crew and this consisted of a mix of Armor-Piercing (AP) and High-Explosive (HE) rounds to be used against "hard" and "soft" targets respectively as required. The gun mount allowed for +20 and -10 elevation while the turret allowed for a full 360-degree traversal. Between three and four Modello 38 series 8mm machine guns were fitted throughout the design. One machine gun was fitted coaxially with the main gun in the turret and operated by the gunner. The machine gunner/radio operator managed a double 8mm machine gun pairing in the front hull by way of a flexible ball-mount. While the pairing could be seen as advantageous, the firing arc and the position's vision was relatively limited. If equipped, a fourth 8mm machine gun could be installed on the turret roof and serve double-duty in combating both enemy infantry or low-flying attack aircraft. Up to 3,048 x 8mm ammunition was provided for all of the available machine gun emplacements.
In practice, the light nature of the Carro Armato M13/40 shown through. At the time of her inception, she was a solid offering, owning much to her British-inspired track system and use of a diesel engine over that of conventional gasoline-fueled types. Ammunition for the 47mm gun was ample and capable of dealing with light armored targets (up to 45mm in armor thickness) at ranges out to 500 meters. All was not perfect, however, for inherent mechanical issues were ever apparent during the life of the tank and the interior fighting compartment was cramped at best. Regardless, the tank was a new fixture and could prove valuable in a fight, particularly in the style of the Italian Army to this point.
The M13/40 saw combat actions in both the Balkans and in the Western Desert campaigns of the North African in World War 2. In the early phases of the North African Campaign, they seemingly held their ground against the enemy tanks where her 47mm main gun was capable of dealing with all manner of light armor and troop concentrations. The early British "cruiser" tanks were her contemporaries and the 47mm main gun proved useful. However, as experience and equipment improved for the Allies, these Italian "medium" tanks proved much less effective for many were lost in ensuing actions to more powerful enemy guns. While other global military powers had adapted their fighting styles and technologies to the changing battlefield, the Italians did not, suffering the consequences as a result. Enough M13/40 tanks were abandoned by the Italians and subsequently captured by British and Commonwealth forces that they stocked the ranks of the British 6th Royal Tank Regiment and the Australian 6th Cavalry Regiment only to be used against their former masters. These tanks were accordingly marked to help avoid incidences of "friendly fire" in the vast desert campaign. As the Allies were desperately short of capable armor at the time, the use of enemy equipment was almost a requirement for future successes until Allied production of tanks ramped up. M13/40s participated in the famed Second Battle of El Alamein which went down in history as a major Allied victory and would signal the beginning of the end of the North African Campaign.
As time wore on, the M13/40 showcased her limitations in the forefront of the ever evolving war effort. Her 47mm main gun now proved ineffective against the latest generation of Allied tanks including the Matilda, Grant/Lee and M4 Sherman. Her powertrain was put through its paces in unforgiving conditions resulting in many mechanical break downs while her thin armor protection (utilizing riveting) did little against Allied armor-piercing shells from anti-tank gun crews, battle tanks and artillery barrages. When directly hit, rivets could become flying "bullets" within the fighting compartment for the crew. Additionally, M13/40s were known to be fire-prone when hit - a tanker's worst nightmare in being burned alive within his mount. Many M13/40s were lost to both enemy action and abandonment which did not help the Axis cause in the desert. Despite this, her production numbers were sufficient enough that she saw active service up until the end of the war in 1945.
The M13/40 was formally replaced in the Italian Army inventory by the improved M15/42 series. Though production of this new type was rather limited, it featured a more powerful 47mm main gun and a modular engine compartment.