Try searching with it's correct (German) spelling ("Bataillon" instead of "Battalion" , "Pionier" instead of "Pioneer" for example) and (in the case of German units) drop the initials (such as "Geb.", "Aufk." ,"Nachr.", etc), replacing them with the complete words ("Gebirgs", "Aufklarungs", "Nachrichten", etc)...
Lexikon der Wehrmacht - Gebirgs-Pionier-Bataillon 818
Dave