Short answers, pulled from the story.
Poland accepted Western Christianity in 966 under the ruler Mieszko I, marking the beginning of its statehood. A missionary bishopric was established in Poznań two years later in 968.
The First Partition of the Commonwealth occurred in 1772 when Prussia, Russia, and Austria took place to divide Polish territory. The Partition Sejm ratified this act under considerable duress as a fait accompli.
Around 6 million citizens perished during World War II, representing more than one-sixth of Poland's pre-war population. This includes approximately 3 million Polish Jews killed in six German extermination camps and between 1.8 and 2.8 million ethnic Poles.
Poles voted to join the European Union in a referendum in June 2003 with Poland becoming a full member on the 1st of May 2004. This followed the transformation of its Soviet-style planned economy into a market economy by Leszek Balcerowicz in the early 1990s.
Stanisław II Augustus Poniatowski reigned from 1764 until his abdication on the 25th of November 1795. On the 24th of October 1795, the Commonwealth was partitioned for the third time and ceased to exist as a territorial entity.