Semovente 75/18

The Semovente 75/18 was an Italian self-propelled gun of the Second World War. It was built by mounting the 75 mm Obice da 75/18 modello 34 mountain gun on the chassis of a M13/40 or M14/41 tank. The first 60 were built using the M13/40 chassis and a subsequent 162 were built on the M14/41 chassis from 1941 onwards. The Semovente 75/18 was intended to be an interim vehicle until the heavier P40 tank could be available.

History
An Italian artillery Colonel named Sergio Berlese (who designed the Obice da 75/18 modello 34) suggested that Italy should create an armoured fighting vehicle similar to the German StuG III, which had been successful in the French campaign. The first prototype was quickly assembled and delivered, on February 10, 1941, only 13 months after the first M13/40 tank upon which it was based. After that, 60 more examples were ordered. They were delivered in 1941, and were then shipped to North Africa in January 1942. This initial batch was based on the M13 chassis, with its weak 125 hp engine (later to be replaced by one of 145 hp, with M14 chassis).

Structurally, this self-propelled gun was built with riveted steel plates, which were thicker but also less sloped than in the original tank (50 mm as against 42 mm max). Frontal armour was almost vertical, but it consisted of two plates that strengthened it when compared to a simple homogeneous steel plate.

Mechanics and technology
The vehicle had its crew compartment and drive section forward, in a large and low casemate. The engine was situated behind it, in a typical Italian design fashion. The engine compartment was not included in the same structure with the same width and height of the crew's space, but rather in a separate structure, which was sloped, somewhat smaller and had inspection panels on the roof. The mechanics were similar to those of M13/40 tanks, with eight small wheels in four trolleys which were joined in pairs by two arms. Suspensions were of the leaf spring type, which was reliable, but had low performance for speed. The transmission was located in the forward part of the vehicle, and the crew consisted of only three members: driver, gunner, and tank commander.

The main gun was a derivative of a 75/18mm gun, itself a quite modern divisional artillery piece. It was 18 calibers long, with 40° traverse and -12/+22° elevation. The gun had a muzzle brake, and there were several observation and aiming systems (binoculars, periscopes and others) for the crew. The low muzzle velocity (around 450 m/s) meant a relative short range, 9,500 m at best elevation of 45 degrees, but the installation allowed only 22° and so the range was limited to around 7–8 km. The range in direct fire mode was also limited, especially against moving targets, for the same reason. Only one roof-mounted machine gun was fitted for close defense, though sometimes it was omitted. Initially this was a 6.5 mm Breda, later upgraded to an 8 mm model. Ammunition load was typically 44 75 mm shells and 1,108 8 mm cartridges. A model RF1 CA with interphone radio was usually fitted, with the gunner also serving as radio-operator.

Service
Although these machines were not widely known, the vehicle performed well in its role. Though it was technically similar to the StuG III, it had a totally different role, serving as divisional artillery instead of a pure assault gun. The organic structure consisted of two artillery groups for every armoured division, with two batteries each (four 75/18 each and a command vehicle). The total was of 18 75/18mm (included two in reserve) and 9 command vehicles, which were characterized by additional radio equipment and a 13 mm machine gun mounted instead of the main gun. The number originally ordered, 60 total, was enough for the three armoured divisions.

The Semovente 75/18s were widely deployed in the North African campaign and during the Allied invasion of Sicily, alongside M13/40 units to provide additional firepower. In North Africa they were quite effective against the US built M3 Grant and M4 Sherman tanks used by the British Army.

Originally, these Italian vehicles were meant as divisional artillery, but since they sported fully enclosed fighting compartments, they were well protected enough for front-line action. They could fire as indirect support, and if necessary, also act as an assault gun and anti-tank vehicle. It could be used with HE, AP and HEAT shells, and with these latter the vehicle was powerful enough to defeat Allied tanks such as the M4 Sherman. In fact, these machines were responsible for many of the successes by the Italian armoured troops during 1942-43.

In 1942, more vehicles were built: 132 or 146, but all with the M41 hull. They fought mainly in a defensive role, as their lack of turret and low profile made them ideal for this task.

The SPG 75/18 was a successful design, and despite the modest quality of Italian armoured vehicles, it performed well in service. It was employed by Italian artillery in a very innovative fashion, because these were the first SPGs employed at a divisional level. However, the rest of Italian army was seriously lacking in mobility for its artillery and these few machines (not debuting in combat until 1942) could not change the overall deficiency.

The capabilities of the 75mm HEAT round were significant because this was the only weapon mounted in Italian AFVs that was able to defeat the heavier enemy vehicles, with the likely exception of the Churchill tanks. Without this shell, the 75/18 was not as impressive, due to the low AP velocity and range.

For a self-propelled gun, its ammunition load was barely enough, as were the power and the range of the gun. The taller and open-topped later vehicles such as the M7 Priest, Sexton, and Wespe, had superior ammo loads and range. The rate of fire for the SPG 75/18 was quite slow, due to the limitations of the 3 man crew. The lack of a coaxial machine gun was also an important difference with respect to a 'real tank'. Only in 1943 were tracked supply vehicles utilized, carrying 99 shells to quickly reload these SPGs. The quantity produced, although not low by Italian standards, was nonetheless insufficient for the dual role of tank-SPG.

Starting in 1942, these vehicles fought in all of the important desert battles, with the apex at the Second Battle of El Alamein until the retreat to Tunisia, serving mainly as direct fire anti-tank and fire support.

The necessity for a longer and more powerful gun led to the development of the 75/34, 75/46 and 105/25 SPGs.

German use
After the Italian surrender in 1943, 123 Semovente 75/18 were seized by the Germans and they continued production of another 55. They were issued to six infantry divisions, two panzer divisions, three Panzergrenadier divisions, 22 SS Volunteer Cavalry Division Maria Theresa and one Gebirgsdivision intended for service in Italy and the Balkans.