However, even as the tank began its trials, it was clear that the German military missed its mark. While the Grosstraktor was overcomplicated over its five years of development by three companies (it's enough to say that it was also amphibious), the Nb.Fz. was in an even bigger hole. The initial project, designed by Rheinmetall (chassis and turret) and Krupp (second turret variant) was supposed to fit into the 15 ton class. As a result, the appetite of the 6th Waffenprüfamt led to a complex and expensive 23 ton tank.
A new tank concept split up tanks into support tanks and tank destroyers. The tank destroyer role was filled with the 10 ton Zugführerwagen (future PzIII). The Z.W. specification was developed in late 1933, even before the first Nb.Fz. was built. As for the Nb.Fz., it's fate was sealed in the fall of 1934. Initially, the new tank was called verbesserten Nb.Fz (improved Nb.Fz.) in documents, but a new index was used in correspondence between Krupp and the 6th Waffenprüfamt starting on November 14th, 1936: B.W. or Begleitwagen, support vehicle.