Up until the creation of Mieszko's state and his subsequent conversion to Christianity in 966 AD, the main religion of Slavic tribes that inhabited the geographical area of present-day Poland was Slavic paganism.With the Baptism of Poland the Polish rulers accepted Christianity and the religious authority of the Roman Church.Following the Partitions of Poland at the end of the 18th century, Poland regained its independence in 1918 with the Treaty of Versailles.
In 1264, the Statute of Kalisz or the General Charter of Jewish Liberties introduced numerous right for the Jews in Poland, leading to a nearly autonomous "nation within a nation".
In the middle of the 13th century, the Silesian branch of the Piast dynasty (Henry I the Bearded and Henry II the Pious, ruled 1238–41) nearly succeeded in uniting the Polish lands, but the Mongols invaded the country from the east and defeated the combined Polish forces at the Battle of Legnica where Duke Henry II the Pious died.
Other major cities include Kraków, Łódź, Wrocław, Poznań, Gdańsk, and Szczecin.
The establishment of a Polish state can be traced back to 966, when Mieszko I, ruler of a territory roughly coextensive with that of present-day Poland, converted to Christianity.
The Kingdom of Poland was founded in 1025, and in 1569 it cemented a longstanding political association with the Grand Duchy of Lithuania by signing the Union of Lublin.
This union formed the Polish–Lithuanian Commonwealth, one of the largest (about 1 million km which adopted Europe's first written national constitution, the Constitution of .Poland's first historically documented ruler, Mieszko I, accepted Christianity with the Baptism of Poland in 966, as the new official religion of his subjects.The bulk of the population converted in the course of the next few centuries.The origin of the name Polanie itself derives from the early Slavic word pole (field).In some languages, such as Hungarian, Lithuanian, Persian and Turkish, the exonym for Poland is Lechites (Lechici), which derives from the name of a semi-legendary ruler of Polans, Lech I.The Black Death, a plague that ravaged Europe from 1347 to 1351 did not significantly affect Poland, and the country was spared from a major outbreak of the disease.