The 9×25mm Mauser returned to prominence after World War I as a viable, powerful cartridge for submachine guns. As Germany was restricted by the Treaty of Versailles from manufacturing certain small arms, it outsourced production to companies in other countries, including Belgium and Switzerland. Rheinmetall approached Solothurn Waffenfabrik AG in Switzerland to manufacture the MP19, an improvement on the MP18 designed by Louis Stange and Theodor Rakula. As Solothurn did not have the production capacity for large-scale manufacturing, Rheinmetall acquired a controlling interest in Waffenfabrik Steyr of Steyr Daimler-Puch AG, an established arms manufacturer in Austria, creating the business consortium Steyr-Solothurn Waffen AG. The Solothurn trademark changed from a single S to a double S with a W in the center.
