"One of the distinguishing characteristics of German tank building in WWII was an aim to use up obsolete vehicles, including those which used to be the backbone of the German tank force. If a German tank became obsolete, that didn't mean that it would be scrapped. Some tanks were sent to training units, other were modernized. Obsolete tanks, especially light ones, were often converted to SPGs or engineering vehicles. This was the fate that awaited the PzI, Germany's first mass produced tank, which was already obsolete at the start of WWII.
Minor mechanization of infantry artillery
German infantry units were armed with a wide variety of artillery by the end of the 1930s. Aside from anti-tank guns and mortars, the infantry had howitzers and so called "infantry guns" (Infanteriegeschütz). The parameters of these cannons (barrel length, high elevation angles) made them closer to howitzers, but, formally, they were listed as regimental artillery.
German infantry used two types of infantry guns: the light 7.5 cm leIG 18 and heavy 15 cm sIG 33. The heavy gun was the most interesting, as nothing of the sort was used by any other military. Some of its characteristics were similar to those of a mortar, which was not surprising. The main objective of the sIG 33 was combat with enemy fortifications. Initially, the gun was towed with horses, but later a version that could be towed by artillery tractors appeared. It is easy to distinguish between the two: the motorized version has rubber rims on its wheels, which increased its top speed…"
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