To form the spearhead of the Italian tank force in the rearmament period of 1940 a completely new tank was designed under the direction of General di Feroleto who was appointed Inspector- General of mechanised forces with the specific task of modernising the range of available AFVs. The M 13/40 design was based broadly on the M 11/39 but was bigger, carrying the main gun — a new high velocity 47mm weapon — in the turret, with the secondary MG turret moved to the hull (reverse arrangement to the M 11/39. Thicker armour and other refinements were also incorporated. First deliveries of production vehicles, built by Fiat and Ansaldo, started in mid-1940, 250 vehicles out of the 1,900 initial order being delivered by the end of 1940. First experience with these vehicles in the desert showed the need for added filters and other 'tropical' parts. These were duly fitted and the opportunity was taken, with later machines, to substitute an uprated engine. Vehicles so fitted — and all late production vehicles — were known semiofficially as M 14/41 but there were few external differences. However, early vehicles had dust guards only at the front end forward of the turret line while later vehicles had full-length dust guards. The M 13/40 was first in action in December 1940 in Libya and proved to be a very practical design with a good high velocity gun, though it was no match for the heavy British infantry tanks like the Matilda. Subsequent production included a Semovente SP gun on this same chassis which eclipsed the value of the original tank design.