sentences:  The world's first submachine gun (a fully automatic firearm which fires pistol cartridges) able to be maneuvered by a single soldier is the MP18.1, invented by Theodor Bergmann.It was introduced into service in 1918 by the German Army during World War I as the primary weapon of the Stosstruppen (assault groups specialized in trench combat).Submachine guns came to prominence during World War II, with millions manufactured.