Wikipedia
Sonderführer (short: Sdf | or Sf = Sonderführer with military command power ) – in the meaning of specialist leader (literal: special leader) – was the function assignment, introduced in the Wehrmacht of Nazi Germany in 1937.
It was established for the mobilization of the German armed forces. With the draft of Sonderführer to military service, the competence of civil experts and specialists could be exploited. Certain assignments from senior officers, company-grade officers, up to non-commissioned officer (NCO) ranks could be filled. A huge variation of service functions, e.g. in foreign languages, propaganda work, medical service, veterinary service and the like, was possible. Typically, the men were not trained as soldiers. They received the pay applicable to the position they were holding, but only by virtue of their temporary appointment. As a rule, Sonderführer were not allowed to execute the command and disciplinary powers vested in the rank. However, this was changed in 1942, during World War II.
Sonderführer were used not only in Wehrmacht and Waffen-SS, but also in other Nazi-organisation, e.g. in the Organisation Todt, Reichsarbeitsdienst, etc.
In soldier´s slang Sonderführers, as well as Wehrmacht´s officials (de: Wehrmachtsbeamte) and military chaplains, were called narrow-gauge officers (de: Schmalspuroffiziere).