Unlike official airmail stamps, semi-official airmail stamps were issued by aviation companies, air shows, and other aviation-related organizations. The semi-official airmail stamps paid the fee for transport of the mail on a particular airplane, glider, or balloon flight.
After World War II, a set of stamps appeared which, as the story went, were printed for use by the civilian postal system in combined Alpenvorland-Adria (a combined district which apparently never actually existed).
Following the defeat of Italy in 1943, Germany assumed responsibility for the Ionian Islands.
During the German occupation, overprinted Hitler-head issues were the primary postage for occupied Ukraine. In addition, at the beginning and end of the German occupation, several local administrations issued emergency local issues to fill the void left between the changing national governments.
During the occupation period, Serbia issued a large number of postage stamps.
Upon the invasion of Russia, Germany established the Reichskommissariat Ostland to govern Estonia, Lithuania, Latvia, eastern Poland, and western Belarus.