The weapon was developed in 1917 on request from Imperial German Army, which required a compact, yet highly effective weapon for short-range fighting in trenches of World War One.
Schmeisser’s design was a simple and effective blowback operated, full automatic only weapon that fired from open bolt which fired the standard Luger pistol cartridge. The tubular receiver was attached to the front of the wooden stock, and could be pivoted barrel down for maintenance and disassembly.
Prototypes were with double-row box magazines which held 20 rounds, but Army insisted on adoption of a 32-round snail-drum magazine (TM08), originally produced for the Luger P08 "Parabellum"pistol.
Nevertheless, weapon historians feel, that around 25-30,000 of M.P.18.I submachine guns were built before Armistice in 1918, and likely no more than 12,000 of those reached German troops at the fronts.
Soon after the end of WW1, Schmeisser converted his weapon back to more convenient and reliable box magazines and he added a manual safety, located on the left side of receiver, behind magazine housing. This weapon saw limited use by police of Weimar Republic.