История почты и почтовых марок Срединной Литвы (ru); Postage stamps and postal history of Central Lithuania (en)
Stamps of Central Lithuania = Stamps of the Polish occupation of Lithuania, 1920-1922
The state territory of Central Lithuania (green), 1920-1922
In the course of the Polish-Soviet War 1919-1921 occupied Polish military units under the command of General Lucjan Żeligowski in September 1920 the area around of Vilnius (Polish: Wilno; German: Wilna) in the then new founded state of Lithuania.
Pro-Polish separatists proclaimed on the 18th of October, 1920 their own state Central Lithuania (Polish: Środkowa Litwa; German: Mittellitauen) with a Pro-Polish interim-government and an own parliament.
According to a resolution of the Pro-Polish parliament from the 20th of February, 1922 requested the government of Central Lithuania for an entry in the state area of Poland (Second Polish Republic).
The state area of Central Lithuania was annected by Poland with the 16th of April 1922.
With the enactment of the Molotov–Ribbentrop Pact from the 23rd of August, 1939 was the state of Poland liquidated and the then Polish administrated region of Central Lithuania was split in a Western part (with Vilnius) as part of Lithuania and later part of the Lithuanian Soviet Socialist Republic and in an Eastern part as part of a reunified Belarus.
The stamps with the country name Środkowa Litwa or Litwa Środkowa(= Central Lithuania) were valid as postage to the 16th of April, 1922. From the 16th of April, 1922 to September 1939 were valid the stamps of Poland.