Submachine gun
World War II developments were many and interesting. In Germany the development of machine carbines (Maschinenkarabiner) was notable.  From 1939 onwards the German Army analyzed combat conditions and developed new tactics and equipment requirements. The existing 7.92x57mm rifle cartridge was more powerful and long ranged than needed. Most combat took place at ranges less than 400 m (440 yards). A less powerful round (bullet) could be used. This meant a soldier could carry more ammunition, the weapon could be shorter, lighter and with less recoil. The gun could be an automatic.