As early as 1926 various German companies, including Rheinmetall and Daimler-Benz, produced a single prototype armed with a large 75-millimeter cannon (the Großtraktor, "large tractor", was so codenamed to veil the true purpose of the vehicle).[11] Only two years later prototypes of the new Leichttraktor ("light tractor"), were produced by German companies, armed with 37-millimeter KwK L/45 guns.[12] Development of the Neubaufahrzeug (German for "new construction vehicle") started in 1933 when the then Reichswehr gave a contract for the development of a Großtraktor to both Rheinmetall and Krupp. Großtraktor was a codename for the development of a heavy tank, Germany being still forbidden to develop tanks under the terms of the Treaty of Versailles. The Rheinmetall and Krupp designs resembled each other to a great extent, the main difference being the weapons placement.