The first of over 700 M13/40s were delivered following a rate of production of about 60–70 a month, before the fall of 1940. They were sent to North Africa to fight the British; however, most units were hastily formed (and thus lacked cohesion), the tanks had not been fitted with radios (giving them a serious tactical disadvantage even against inferior enemies) and their crews had almost no training (in 1940 the crews were given 25 days of actual tank training and then sent to the front). The baptism of fire came with a special unit, the Babini Brigade. Arriving too late to fight in the September offensive, this unit was ready the next December, for a major British offensive operation. Further action took place in Derna, where the V battalion had just arrived. Tanks of III battalion were also present near this position, at the battle of Bardia. In two days of fighting (January 3–4, 1941), the Australians suffered 456 casualties while the Italians lost 45,000 men captured. On February 6–7, the British offensive penetrated so far that the Babini Brigade sought to open a breach in the British lines at Beda Fomm in an effort to allow cut-off Italian troops to retreat along the Libyan coast. The brigade's action was unsuccessful and all 20 of their tanks were lost. The last six surviving tanks entered a field near the local British command post. They were destroyed one after another by a single 2-pdr (40 mm) anti-tank gun. Many tanks were lost in this campaign to artillery fire rather than other tanks. A number of captured M11 and M13s were re-used by the Australian 2/6th Cavalry Regiment and the 6th Royal Tank Regiment, until the spring of 1941, when their fuel ran out and they were destroyed.
The M13s also fought in Greece, in difficult terrain. Subsequently, in April 1941, M13s of the Ariete division took part in the Siege of Tobruk, with little success against British Matildas. The first successful action for the M13 was the Battle of Bir-el Gobi.
Later use in the desert war
In April 1941, at the time of the arrival of the Afrika Korps, the Italians had around 240 M13 and M14 tanks in first-line service. In 1942, as the Allies began deploying Grants and Crusader IIIs, along with towed 6 pounder anti-tank guns in their infantry units, the weaknesses of the M13 were exposed. In an attempt to improve protection, many crews piled sandbags or extra track links on the outside of their tanks, but this made the already-underpowered vehicles even slower and increased maintenance requirements; such practice, while popular, was discouraged by the commanders for the same reason. The Italians equipped at least one company in each tank battalion with more heavily armed Semovente 75/18 assault guns.
The Second Battle of El Alamein saw the first appearance of the M4 Sherman, while some 230 M13s were still in front line service. In several days of battle, the Ariete and Littorio divisions were used to cover the Axis retreat. The Centauro Division was virtually destroyed fighting in Tunisia. By then, the M13/40 and the M14/41 were completely surpassed, and their armament was all but useless against the enemy's M3 Lee and M4 Sherman medium tanks at all but point-blank range (however, both could easily destroy an M13/40 from a distance); they resorted to firing at the suspensions and the tracks, and to rely on fire support by the Semoventi and artillery.