1940 Airmail Set:
1: 1940 King Boris III Definitives
2,3: Postage Stamp Centenary (1940)
4-6: Occupation of South Dobrudja (1) (1940)
7 : 1940 King Boris Definitives
8 -13: Famous Bulgarians (1940)
1-10: 1940 Definitives: Agriculture
11,12: 1940 Invention of Printing Quincentenary and Bulgarian Printing Centenary (2): J. Gutenberg (3) and N. Karastojanov (first Bulgarian printer)
1-3: H. Botev 65th Death Anniversary (1941)
4-6: 1941 Definitives: Sofia Buildings
7-11: 1941 Reoccupation of Macedonia and Thrace (4)
13-16: Work and Joy Propaganda (1942)
17-30: Bulgarian History (1942)
31-36: War Invalids (1942)
37: 1944 Definitive Stamp: King Simeon II
1944 King Boris III Commemoration Set (perforated and imperforate):
(1) With German armies at the border, Bulgaria was forced to join the Axis Powers to avoid a direct invasion. This was generally accepted by the population, mostly because Germany in 1939 had signed a pact of non-aggression with the Soviet Union, which by most Bulgarian still was identified with the Russia which liberated their country in 1878. After the German occupation of Scandinavia and France, Stalin demanded "compensations" in the east. This was carried out at the expense of Romania, which after Soviet pressure had to cede Northern Bukovina and Bessarabia to the Soviet Union, North Transylvania to Hungary as well as returning Southern Dobrudja to Bulgaria, which had been lost to Romania in 1913. The Paris peace treaty which was signed in 1946, made provision for the territorial integrity of Bulgaria within its borders of 1939 and acknowledged the annexation of Dobrudja.
(2) After the publication of the first Bulgarian book in Bucharest in 1806 (Vrachenski’s collection of sermons), the number of publications outside the Ottoman Bulgaria increased steadily during the beginning of the 19th century. The first Bulgarian printing press inside the borders of the Ottoman Empire was, however, not established until 1840. One printing press in Smyrna in Little Asia was owned by a Greek who had imported Cyrillic types from the US at the request of the British and Foreign Bible Society. In the same year another Bulgarian press was established in Saloniki. Both printing presses had primarily a religious function, but were also used for secular purposes.
(3) Johannes Gutenberg (1398–1468) was a German metal-worker and inventor. He achieved fame for his contributions to the technology of printing during the 1450’s, including a type metal alloy and oil-based inks, a mould for casting type accurately, and a new kind of printing press based on presses used in wine-making. Tradition credits him with inventing movable type in Europe, an improvement on the block printing already in use there. By combining these elements into a production system, he allowed for the rapid printing of written materials and an information explosion in Renaissance Europe.
(4) As Bulgaria joined the Axis Powers, Germany could attack Yugoslavia and Greece in April 1941 by sending troops over Bulgarian territory. Within one month the whole Balkan peninsula was occupied, and the region was divided between the Axis Powers and their allies. Bulgaria got back Western Thrace and Macedonia, the lands lost in 1918.