I mistakenly called him "Otto" in an earlier post. He is quoted on pages 52, 123 and 174 in Anthony Brett-James "1812", as well as Haythornethwaite/Chappell's "Uniforms of Napoleons Russian Campaign" (p.154). He is described in the former as "Captain Fritz - whose name it has not beeen possible to trace, but who came from an ancient military and titled family in Pomeranian Mecklenberg, had campaigned in the Peninsula under Wellington's command before deciding to offer his services to Russia."
In the same book "Fritz" himself related that he had done two summer campaigns in Portugal and Spain (1810?, 1811?). He was later in the Elisavetgrad Hussars and was attached to the staff of Prinz Karl von Mecklenburg at the 1812 battle of Borodino where we was wounded. He recovered with relatives in the Ukraine.
I have notes that he fought at Jena-Auerstadt and then was with the "Black Brunswickers" but regrettably cannot remember from where I got this information. Originally I thought he must have been with the KGL in Spain but it may be he was still with the Brunswickers. If so I expect he left them after the problems of the Legion in the Peninsula where they suffered from dilution through the recruitment of deserters of various nationalities from the French Army.
I did possess the Osprey Brunswick Troops 1809-15, but sold it ages ago. Perhaps my details for his early career came from there? There was another Haythornethwaite book that springs to mind but I cannot recall the title. I borrowed it from Aberdeen Central Library in 1991 or 1992....
Also he claims (in another book I cannot locate) that he met and talked with Bluecher in 1815, while serving in one of the Prussian Army units. Possibly a Pomeranian National Cavalry regiment? Again this is conjecture on my part.
Anyone who can add to these details is welcome. "Fritz" deserves more recognition. "Fritz" as we know, is a dimiutive of Friedrich.
K