Hi Brian,
I initially thought this might be quite a common name, but if as spelt there are only a couple of real possibilities. The only infantry officer I can find albeit Landwehr, is an Hauptmann der Landwehr a.D. serving with the convalescent battalion at Wündsdorf. I assume we can rule out the Jäger-Regiment zu Pferde Regiment Nr. 1 Leutnant (killed as an aviator) and General der Infanterie Max Kaempffer!! There was also a Oberleutnant d.R. in Grenadier-Regiment Nr. 10 spelt with an Umlaut - Kämpffer, another in RIR 80.
Regards
Glenn