the weight increase (which now topped at 26 tonne) and the difficulties in finding a suitable engine further hampered the start of mass production; in the end, it was decided that the prototype and the early production samples were to be equipped with a 330 HP SPA 8V diesel engine, later to be replaced by a 420 HP petrol engine. Only a few (between one and five depending on the source) pre-production models were completed before the Italian Armistice in September 1943, at which point they were taken over by the German Wehrmacht. A few were used in combat, under the German designation of Panzerkampfwagen P40 737(i), for example at Anzio; some, without engines, were used as static strongpoints. Combat history Only 21 P 40s were finished; during the armistice it served in the defence of Rome. The Germans ordered production to continue after the armistice and appropriated completed tanks to the Southern Tank Training Battalion, 10th and 15th Police Panzer Companies, and the 24th Waffen Mountain Division of the SS Karstjäger. The Southern Tank Training Battalion trained units to use captured Italian tanks and had five P 40s in their inventory. The 10th Police Panzer Company served in Russia before redeployment to northern Italy in late 1944 for anti-partisan duties with the 15th Police Panzer Company. Formed in summer of 1944, the 24th Waffen Mountain Division was deployed to Trieste and Udine along the Adriatic coast. While retreating towards Austria in March 1945, they lost several P 40 tanks to Shermans of the British 6th Armoured Division. About a hundred P 40s were used by the German military, of which about 40 were without engines and used as static emplacements at defensive positions such as the Gustav and Gothic Lines. Design The turret was operated by two crew members and this was a significant drawback as it put excessive workload on the tank's commander. At that time, most new tanks were designed with three-man turrets. Moreover, it lacked a commander's cupola. The main weapon was the 75/34 gun, a development of the Model 37 divisional gun (34 calibres long), retaining the same dimensions. This weapon had a muzzle velocity of around ; and was normally provided with around 75 rounds of ammunition. Its armour-piercing shells could penetrate roughly 70 mm of armour at 500 meters. For secondary armament, the P 40 had a co-axial machine-gun and another which could