Republika Srpska Krajina:
Part of Yugoslavia, today it is part of Croatia.
Short lived Republic, at the time of last civil war in Yugoslavia, which proclaimed independence as response to Croatian proclamation of independence and partition from Yugoslavia Federation.
One very ugly period of civil war there, and in the end, this young independent country was brutally overrun by Croatian forces.
In short period, this Republic issued own postage stamps, that are listed in most of world catalog, except Scott (Scott have own policy and decided not to list this country, for unknown reason, even as this Republic have own Postal System, which operated well inside own territory and also between other Republics).
This postage stamps is NOT cinderella, or as someone say propaganda postage stamps, as it was legally used on mail, mostly inside own territory, and rarely with other countries. At the time of civil war, ugly fighting, no many people used post offices and mail for correspondence, so real, postally used samples are very rare, with one high catalog value in Michel catalog, and even more valued on open market, which is very short on material in PU condition.
