Here are some things I tried which you may have already used.
"Find a grave"
Military records are stored in St. Louis , Mo.
Lutheran Church in Germany
Native German geneology researchers can help in locating cemeteries, etc in Germany
Confederate soldier records
Some of our Garms clan did indeed leave Illinoiis for Oklahoma. Not from Peter Hinrich Garms or Detlef Garms though. Those two brothers are the original Garms in Brown County, Texas. Through my geneology research I've been able to gather enough information to establish Garms as a historical family in Brown County, Texas, present since before 1900.
Keep the search going