The StuH 42, SdKfz 142/2, or Sturmhaubitze 42 was a self-propelled gun that was used by Germany during World War II. It had a Maybach HL 120 engine that was capable of propelling it at speeds of up to 40 km/h. It was based upon the StuG III Ausf. F chassis with its most notable difference being the addition of an L/28 howitzer for its main gun. The purpose of this addition was so that the Wehrmacht would have an effective combat support unit that would work well against infantry.
Additional Information: http://world-war-2.wikia.com/wiki/StuH_42