This self-propelled howitzer carried the 155mm Long Tom gun on a Sherman tank chassis. This provided armored units of World War Two with fast, long range artillery support that could keep up with armored formations. Ironically, while the Germans developed the Blitzkrieg system of tactics, it was American industrial capacity that allowed it to be used to the fullest, with mechanized artillery like this gun making it possible. The M41 was a similar vehicle, but mounted the 203mm howitzer, and is a simple conversion.
M40 SP 155mm Howitzer