From the early Middle Ages, West Slavic communities formed varied political groupings between the Baltic and Central Europe. The Piast rulers consolidated power, and Mieszko I’s baptism in 966 connected the principality with Latin Christian institutions. The kingdom developed through dynastic change and regional fragmentation. Its union with Lithuania grew into the Polish-Lithuanian Commonwealth, an extensive political community of Polish, Lithuanian, Ruthenian, Jewish and other inhabitants.
The Commonwealth was an aristocratic parliamentary republic with religious diversity and extensive privileges for the nobility, but political rights were unequal. Wars and internal power struggles weakened the state; between 1772 and 1795, Russia, Prussia and Austria partitioned its territory. Polish uprisings, culture and language persisted under foreign rule in the nineteenth century. The restored independence of 1918 brought new border conflicts and a multinational population within the new republic.
Germany and the Soviet Union invaded Poland in 1939. German occupation brought the Holocaust and the murder of millions of Polish Jews, as well as repression and forced labour; after the war, the border shifted west and populations were forcibly displaced. The communist state transformed property and society, while opposition and church networks provided space for resistance. The 1989 negotiations led to a democratic transition; Poland has been a member of the European Union since 2004.