I have asked this question several places without finding an answer. Maybe somebody here can help.

Austro-Hungarian K.u.K. Feldpost system was intended principally to carry mail (letters, parcels, printed matter, etc) "between the army and home." It was active anywhere there was a military presence, particularly in territories occupied by A-H army. My question is, did this service ever act as an occupation mail service, available for civilian use?

In Romania and Italy, K.u.K. Feldpost stamps were overprinted and redenominated in local currency. Why would that have been necessary if they were not intended for civilian use? And, what about Russian Poland, for instance? Covers are often found with Feldpost postmarks from Austrian occupied cities (Lublin, for example), or designated "Rus.Polen." The same goes for locations in Serbia and the Ukraine. Are these only military mail?
Thanks,
jno