Hi,
the "German Wehrmacht" used beside standard gauge and broad gaude (1524 mm) 750 mm as "standard" narrow gauge during WW II, Other gauges like 600 mm and 1000 mm were used in addition on exsiting N G RR in the occupied countries. Since there was no 750 mm gauge in France (the military there choosed 600 mm as standard for military and most official carriers in late 1870ies) it must be a two foot or 1000 mm gauge. Most steam and diesel engines were multigauge and could be used from 2 ft up to 760 mm (Bosnian Gauge in Yugoslawia and Romania) soe even to 1000 mm.