The MP18.1 manufactured by Theodor Bergmann Waffenbau Abteilung was the first practical submachine gun used in combat. It was introduced in service in 1918 by the German Army during World War I as the primary weapon of the Stosstruppen, assault groups specialized in trench combat. While MP18 production ended in the 1920s, its design was the base of most of the submachine guns between 1920 and 1960. The firepower of this new class of weapons made such an impression on the Allies that the Treaty of Versailles banned further study and manufacture of such light automatic firearms.