The MP 38 and MP 40 (MP designates Maschinenpistole, literally "Machine Pistol" and known as Schmeissers by the Allied Forces) were submachine guns developed in NaziGermany and used extensively by paratroopers, tank crews, platoon and squad leaders, and other troops during World War II.
As an officer Hasso Pemsel, had been issued a MP 40 submachine gun and highly appreciated its capacities and firepower. He still had it when he sat upon the Omphalos Stone and was carried into another world. He immediately used it there to save the life of Velona by killing her Grenye pursuers. As the Schmeisser was far superior to the medieval weapons of this world, Pemsel quickly gained credibility and acceptance among Lenelli. The Lenelli magicians considered it to be a magic weapon and praised the skill of the "magicians of Pemsel's world" whom they credited with making it. Pemsel's use of the gun played an important role in the Lenelli victory in the first battle against the Grenye in which he participated. However, that battle exhausted his supply of ammunition and later on he had to rely on knowledge of historical medieval tactics and the production of firepowder. Still, he was reluctant to part with the trusty Schmeisser, even through it had become in practice no more than a useless piece of metal.
As the German's charged through the Low Countries and into France, the German soldiers used the MP 38 for their close combat fire fights. The French army had never issued submachine guns to their own troops, and so many took the MP38's from dead Wehrmacht troops and use those.