History of Poland
The Polish People's Republic ("Polska Rzeczpospolita Ludowa") was established under the rule of the communist Polish United Workers' Party (PZPR). The name change from the Polish Republic was not officially adopted, however, until the proclamation of the Constitution of the Polish People's Republic in 1952.
Territorial evolution of Poland
On July 17, 1919, a ceasefire was signed in the Polish–Ukrainian War with the West Ukrainian People's Republic (ZUNR). As part of the agreement Poland kept ZUNR territory. The West Ukrainian People's Republic then merged with the Ukrainian People's Republic (UNR). On June 25, 1919, Supreme Allies Council transferred East Galicia (ZUNR territory) to Poland.