In 1138, Poland fragmented into several smaller duchies when Bolesław divided his lands among his sons.
Casimir III realized that the nation needed a class of educated people, especially lawyers, who could codify the country's laws and administer the courts and offices.
His efforts to create an institution of higher learning in Poland were finally rewarded when Pope Urban V granted him permission to open the University of Kraków.
Following the Partitions of Poland at the end of the 18th century, Poland regained its independence in 1918 with the Treaty of Versailles.
In September 1939, World War II started with the invasion of Poland by Nazi Germany, followed by the Soviet Union invading Poland in accordance with the Molotov–Ribbentrop Pact. In the aftermath of the Revolutions of 1989, most notably through the emergence of the Solidarity movement, Poland reestablished itself as a democratic republic.
Casimir III the Great is the only Polish king to receive the title of Great.