
My aunt has found military passports from my great grandfather. He was as a soldier during WWI and he was involved in the German Spring Offensive in 1918, since it is stated in his passport that he has participated in the Große Schlacht von Frankreich, also known as the Kaiserschlacht. In the second WWII he was to old to get into active combat, so he got appointed to the Landwehr and he had to patrol the German-Danish border (if I understood my aunt correctly).
Looking at these passport, one of them being 102 years old, was fascinating, And I felt inspired to pick up "Im Westen nichts Neues", one of the great books about WWI.