The M1A1 Pack Howitzer was the standard howitzer for American forces in World War 2. The Pack design actually traced its roots back to the howitzer development of World War One, standardized in the American Army post-war as the M1. The M1A1 of the Second World War featured a short barrel, could reach a sustained rate of fire of 3 to 6 rounds per minute with a capable crew, and had a range of roughly 9,610 yards (8,790 meters). The system was purposely engineered to be light, easily transportable and operated by a small crew (which worked well in the favor of light divisions such as airborne units as evident in the M8 variant of the Pack). The high explosive shell of the M1 Pack Howitzer weighed 6.3 kilograms. The weapon system could be used for suppression, assault, defense and limited anti-tank duty. Further developments enabled better cross-country mobility.