Origin

The Italian Army realized on the frontline the need for assault guns, leading to the development of the "Semovente" family, large artillery pieces housed in fixed casemates mated over standard tank chassis. The 75/18 and 75/34, 75/46 were all resembling or inspired b the German StuG III. Well armoured and quicker to produce than tanks they were appreciated, notably on the Russian front around Stalingrad, and North Africa. However as their production reached a peak, deliveries went just as in November 1943, Italy was effectively out of the war. Most of these were happily captured by the Wehrmacht that pressed them into service until the end of the war. Most were direct fire weapons but in late 1942, the Italian command realized it also needed an indirect fire type heavy artillery, also self-propelled, in order to support its armoured formations.

Design development by Ansaldo

Ansaldo was contacted and started to took a part of its development team to work on a suitable chassis for the heavy artilery piece of the time, usually tracted, the 149 mm Cannone da 149/40 modello 35, a 40 caliber gun, searching to mate it on an existing tracked chassis, after tryig to design its own, in order to have it installed under a protected casemate.

In the end, Ansaldo settled on the 149/40 and engineers soon found the Carro Armato M15/42 chassis was suitable. This made a good carriage/weapon combination, but as the Italian army asked for more of this gun and the tank itself, the Italian industry fell short and none were available for the development of the new Semovente da 149/40, which development dragged on until mid-1943. There was an iniitial proposal to have it installed on a large casemate, fitted on the P26/40, but the Carro Pesante, only heavy Italian tank in development, was in even higher demand and still ongoing at the time.

Design of the Semovente da 149/40

In order to accomodate the large gun on a somewhat small chassis, the Semovente da 149/40 carried its main gun completely unprotected. There was simply no room to accomodate a casemate and gun cradle. The long gun barrel indeed, complete with its breechblock mechanism which protruted at the back, made the entire light of the chassis. It pointed forwards, and was loaded at the back, the gun muzzle stopping short of the chassis nose.

The Cannone da 149/40 modello 35 was placed on an open mounting carried on the chassis of the regular M15/42 with the turret removed and plated over, a small platform built above. There was still a trap to access ammunitions. The gun crew stood in the open, around the gun. The latter was mounted on trunnions, placed right to the rear, absorbing some - but not all- the recoil forces. The chassis also took part of it.

Unlike cold war SPGs, there was no foldable spade at the rear to firmly anchor the gun when in use. The Cannone da 149/40 modello 35 fire a 46 kg (101 lb) shell to 23,700 metres (25,900 yards), in parabolic trajectories allowing to camouflage it well out of harm. Despite of this, the chassis nose was 127 mm thick (5 inches). This was an adapted naval gun, capable of 60 rounds per hour, also found in many cruisers of the Regia Marina, so there was no shortage of shells. The M42 chassis powerplant SPA 228 petrol engine developed 246 hp, enough to reach 35 kph at best. Like other Italian tanks chassis, their susensions of the old bogie type was sturdy and reliable but obsolete.

By late 1942, the first prototype was ready for firing trials, seen by the Italian top brass, which approved production right away, before even the conlusion of these. However at the time, Ansaldo was crumbling under orders and completely unable to setup a new production line of the Semovente M42 da 149/40 as it was designated by the Army.

There were at least two unsuccessful attempts to start production in 1943, Italy surrendering to the allies when it was just operational and ready to roll. The Germans soon took over the bulk of the Italian Industries in the north, including manufacturers such as Ansaldo. They reassessed priorities and estimated the Semovente da 149/40 was surplus to their own requirement, cancelling the production. Thus, the prototype remained unique, but saw action nonetheless.

Service record

Semovente da 149/40 at max elevation in fire testings, 1943

Apparently the prototype was not used either by the RSI or German forces in Italy. Instead, immediately after the Italian armistice, it was transferred on a rail carriage back to Hillersleben in Germany. Redesignated gepanzerte Selbstfahrlette M 43 with 15 L/42 854 (i) it was tested apparently on a firing range for further evaluation, but this led to no follow-up. U.S. troops eventually captured the self propelled gun in 1945 when reaching the city, and it was shipped back to the United States, ending at Aberdeen proving grounds where it is under display as of today.

Links about the Semovente da 149/40

The Semovente 149/40 on comandosupremo.com
The Semovente 149/40 on militaryfactory.com
The Semovente 149/40 on regioesercito.it
Pafi, Falessi, Fiore, Corazzati Italiani 1939-1945, D'Anna Editore, Roma, 1968.

Semovente M43 da 105/25 specifications
Dimensions (L-W-H)	6.6 m (22 ft) x 3 m (9.8 ft) x 2.01 m (6.6 ft)
Total weight, battle ready	15.8 tons
Crew	5 (commander, driver, gunner, two loaders)
Propulsion	SPA petrol 250 hp (190 kW) petrol, 10.25 hp/t
Suspension	2x4 Leaf Spring Bogies
Maximum speed (road)	21.75 mph (35.00 km/h)
Operational range	150 km (93 mi)
Armament	149.1 mm (5.87 in) L40 modello 35
Armor	From 14 to 127 mm (0.5-5 in)
Total production	1

Semovente 149/40 M42 in German service


Semovente da 149/40 at max elevation in fire testings, 1943


Semovente da 149/40 at Aberdeen


Semovente da 149/40 at Aberdeen, compared to other SPGs of WW2

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