First prototypes of German tank destroyer Sturmgeschütz III (StuG III) were built in 1937 and based on the PzKpfw III Ausf. B tank. Vehicles were armed with short barreled 75mm guns. From spring 1942, StuG IIIs were equipped with StuK 40 75mm guns. Self propelled guns StuG III served in separated assault artillery units, and later in self propelled guns brigades. They were also used in support units of armored divisions.