Dear Ms. Lichtenschopf,
Thank you for posting your request on History Hub!
If Gunther von Schlag was a German soldier at Monte Cassino, you may wish to look into the records located on Microfilm Publication A3356 “German Armed Forces Personnel Files” in the National Archives Collection of Foreign Records Seized (Record Group 242). A description of these records in the National Archives Catalog may be viewed here. There is a finding aid to this microfilm publication that can be viewed by following these steps: (1) go to www.archives.gov; (2) click “Research Our Records;” (3) click “Microfilm Catalog;” (4) in the first search box (Search by Microfilm Publication Number or Keyword) enter the microfilm publication number (e.g. A3356) in the search box and click “search;” (5) click the hyperlinked title of the publication; (6) click “View Important Publication Details” (an Adobe PDF document will open). These microfilmed records can be viewed free of charge in the Microfilm Reading Room (Room 4050) at the National Archives at College Park, MD.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request. Also, all of the research rooms and microfilm reading rooms are closed. We apologize for this inconvenience and appreciate your understanding and patience.
Also, you may wish to contact the Deutsche Dienststelle (WASt), Postfach 51 06 57, D-13400 Berlin, Germany as they have World War II German Armed Forces personnel information. The web site is https://www.dd-wast.de/.
Further, German Army, Air Force, and Waffen-SS Paybooks (Soldbücher), Service Record Books (Wehrpässe), Basic Military Record Books (Wehrstammbücher), and Health Books (Gesundheitsbücher) were returned to the Federal Republic of German by the Department of the Army through the US High Commissioner for Germany during 1953 and 1954. For access to these records, please also contact the Deutsche Dienststelle (WASt).
We hope this information is helpful. Best of luck with your research!