Kingdom of Poland (1320 - 1505)

The period of rule by the Piast dynasty between the 10th and 14th centuries is the first major stage of the history of the Polish nation. The dynasty was founded by a series of dukes listed by the chronicler Gallus Anonymous in the early 12th century: (Siemowit, Lestek and Siemomysł. It was Mieszko I, the son of Siemomysł, who is now considered the proper founder of the Polish state at about 960 AD. The ruling house then remained in power in the Polish lands until 1370. Mieszko converted to Christianity of the Western Latin Rite in an event known as the Baptism of Poland in 966, which established a major cultural boundary in Europe based on religion. He also completed a unification of the West Slavic tribal lands that was fundamental to the existence of the new country of Poland.

Following the emergence of the Polish state, a series of rulers converted the population to Christianity, created a kingdom of Poland in 1025 and integrated Poland into the prevailing culture of Europe. Mieszko's son Bolesław I Chrobry established a Roman Catholic Archdiocese in Gniezno, pursued territorial conquests and was officially crowned in 1025 as the first king of Poland. The first Piast monarchy collapsed with the death of Mieszko II Lambert in 1034, followed by its restoration under Casimir I in 1042. In the process, the royal dignity for Polish rulers was forfeited, and the state reverted to the status of a duchy. Duke Casimir's son Bolesław II the Bold revived the military assertiveness of Bolesław I, but became fatally involved in a conflict with Bishop Stanislaus of Szczepanów and was expelled from the country.

...
Wikipedia