MP-40 ili Smajser
The MP 40 is descended from its predecessor, the MP 38. The MP 36, a prototype made of machined steel, was developed independently by Erma's Berthold Geipel with funding from the German Army. It took design elements from Heinrich Vollmer's VPM 1930 and EMP. Vollmer then worked on Berthold Geipel's MP 36 and in 1938 submitted a prototype to answer a request from the German Armament services for a new submachine gun, which was adopted as MP 38. The MP 38 was a simplification of the MP 36, as the MP 40 was a further simplification of the MP 38, with certain cost-saving alterations, notably in the use of more pressed rather than machined parts.
Other changes resulted from experiences with the several thousand MP 38s in service since 1939, used during the invasion of Poland. The changes were incorporated into an intermediate version, the MP 38/40, and then used in the initial MP 40 production version. Just over 1 million would be made of all versions in the course of the war.
The MP 40 was often called the "Schmeisser" by the Allies, after weapons designer Hugo Schmeisser. Hugo Schmeisser himself did not design the MP 40 but held a patent on the magazine. He designed the MP 41, which was an MP 40 with a wooden rifle stock and a or, identical to those found on the earlier MP 28 submachine gun. The MP 41 was not introduced as a service weapon with the German Army, but saw limited use with some SS and police units. They were also exported to Germany's ally, Romania. The MP 41's production run was brief, as Erma filed a successful patent infringement lawsuit against Schmeisser's employer, Haenel.